WEBVTT

e1a6d0f5-c720-4206-b6ae-9c1973856016/38-0
00:00:07.293 --> 00:00:09.573
<v Guns, Katherine A>Ok, happy to introduce Martijn
van den Ende.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/47-0
00:00:11.143 --> 00:00:13.636
<v Guns, Katherine A>From the Université Côte d'Azur
in southern France. Where he's a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/47-1
00:00:13.636 --> 00:00:13.943
<v Guns, Katherine A>post-doc</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/50-0
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<v Guns, Katherine A>there as well.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/90-0
00:00:17.463 --> 00:00:21.117
<v Guns, Katherine A>In rock mechanics that tracks
university  master's and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/90-1
00:00:21.117 --> 00:00:24.837
<v Guns, Katherine A>bachelors in Urban Sciences,
please work on a number of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/90-2
00:00:24.837 --> 00:00:28.823
<v Guns, Katherine A>topics from Earth made cycle
modeling, possible seismology,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/90-3
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<v Guns, Katherine A>raycasting, and deep learning,
which is Helen with this work.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/101-0
00:00:32.943 --> 00:00:37.043
<v Guns, Katherine A>One thing I really appreciate
about work is limited to his</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/101-1
00:00:37.043 --> 00:00:38.503
<v Guns, Katherine A>Open Access research.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/114-0
00:00:39.263 --> 00:00:41.912
<v Guns, Katherine A>Umm, so there are number of
things in this area, but umm</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/114-1
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<v Guns, Katherine A>also mention two.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/142-0
00:00:42.703 --> 00:00:46.598
<v Guns, Katherine A>The first things most people do
is the boundary line in Open</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/142-1
00:00:46.598 --> 00:00:50.365
<v Guns, Katherine A>Access journals seismicode,
which has been a global effort</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/142-2
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<v Guns, Katherine A>to have Open Access publishing
in seismology.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/160-0
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<v Guns, Katherine A>One cool thing about that is
there's the meeting article that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/160-1
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<v Guns, Katherine A>kind of interests the journals
in five of the abstracts in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/160-2
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<v Guns, Katherine A>languages purely.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/179-0
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<v Guns, Katherine A>Second thing, how to begin this
work to run this paper on</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/179-1
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<v Guns, Katherine A>graphical networks is really
interested in how did it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/195-0
00:01:09.263 --> 00:01:12.232
<v Guns, Katherine A>So we'll just get a page and
we'll be able to post it the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/195-1
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<v Guns, Katherine A>full model and training code. So
it's easy to see what you're</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/195-2
00:01:15.407 --> 00:01:15.663
<v Guns, Katherine A>done.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/200-0
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<v Guns, Katherine A>So I think that's it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/207-0
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<v Guns, Katherine A>Posting code kind of full access
to.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/237-0
00:01:24.063 --> 00:01:27.936
<v Guns, Katherine A>Service attacked in multiple
seismology and just community</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/237-1
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<v Guns, Katherine A>efforts is going to receive the
2024 KA work in about two to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/237-2
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<v Guns, Katherine A>outstanding early career
seismologist.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/244-0
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<v Guns, Katherine A>Us to monitor a number of
phenom.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/265-0
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<v Guns, Katherine A>En traffic, aftershock sequences
and phenomena, these are folks</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/265-1
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<v Guns, Katherine A>today on potential DAS perfect
early in the morning, until this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/265-2
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<v Guns, Katherine A>talk is EW.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/271-0
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<v Guns, Katherine A>What about the dynamic range so
that we get?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/288-0
00:02:01.043 --> 00:02:04.715
<v Martijn Van Den Ende>Alright. Well thank you, Tim and
thank you also for the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/288-1
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<v Martijn Van Den Ende>invitation to to present here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/308-0
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<v Martijn Van Den Ende>I would like to begin by
introducing you to the Abyss</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/308-1
00:02:13.445 --> 00:02:17.423
<v Martijn Van Den Ende>team, which hopefully now you
can see over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/345-0
00:02:19.103 --> 00:02:22.879
<v Martijn Van Den Ende>So the Abyss project is a
project funded by the ERC, which</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/345-1
00:02:22.879 --> 00:02:26.527
<v Martijn Van Den Ende>is the European Research
Council, and the objective, the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/345-2
00:02:26.527 --> 00:02:30.623
<v Martijn Van Den Ende>main objective of this project
is to monitor mega trust faults.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/348-0
00:02:31.383 --> 00:02:32.703
<v Martijn Van Den Ende>With fiber optic cables.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/369-0
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<v Martijn Van Den Ende>And so within this team, led by
Diane River, we have Marie, who</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/369-1
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<v Martijn Van Den Ende>is in charge of data management
and transfer.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/381-0
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<v Martijn Van Den Ende>We have a postdoc, Alastair and
Yuqing and PhD student Clara.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/400-0
00:02:50.823 --> 00:02:56.659
<v Martijn Van Den Ende>And the three sort of main work
packages of this project are,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/400-1
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<v Martijn Van Den Ende>first of all to detect weak
cycling.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/419-0
00:03:01.363 --> 00:03:05.051
<v Martijn Van Den Ende>Make seismic signals and
complement online sizing</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/419-1
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<v Martijn Van Den Ende>networks with offshore
instrumentation.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/424-0
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<v Martijn Van Den Ende>So that is DAS cables.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/439-0
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<v Martijn Van Den Ende>The second objective is to
monitor the crust for precursory</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/439-1
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<v Martijn Van Den Ende>seismic velocity changes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/455-0
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<v Martijn Van Den Ende>So essentially the preparation
phase of large earthquakes and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/455-1
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<v Martijn Van Den Ende>the first one that I'm going to
talk about today is to develop</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/455-2
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<v Martijn Van Den Ende>the 1st.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/468-0
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<v Martijn Van Den Ende>Prototype of offshore Das
Earthwake early warning in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/468-1
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<v Martijn Van Den Ende>Chile.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/511-0
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<v Martijn Van Den Ende>So to give you a bit of context
of the project, we are situated</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/511-1
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<v Martijn Van Den Ende>in Chile, so this is the map we
are focusing on this rectangle</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/511-2
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<v Martijn Van Den Ende>over here in the centre of Chile
where we have access to three</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/511-3
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<v Martijn Van Den Ende>offshore dask cables. These sort
of red little wires that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/513-0
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<v Martijn Van Den Ende>You see here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/527-0
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<v Martijn Van Den Ende>These are sensitive 3 up to DAS
interrogate units. As you can</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/527-1
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<v Martijn Van Den Ende>see over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/537-0
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<v Martijn Van Den Ende>For a total of about 450
kilometers.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/559-0
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<v Martijn Van Den Ende>And the location of the the
project is not by accident</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/559-1
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<v Martijn Van Den Ende>because here we have some major
seismic gaps.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/577-0
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<v Martijn Van Den Ende>So there is a real possibility
that within the duration of the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/577-1
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<v Martijn Van Den Ende>project there are some large
earthquakes occurring in this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/577-2
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<v Martijn Van Den Ende>region.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/588-0
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<v Martijn Van Den Ende>On top of these three
permanently installed</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/588-1
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<v Martijn Van Den Ende>interrogators.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/614-0
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<v Martijn Van Den Ende>We will also soon have one
travelling interrogator that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/614-1
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<v Martijn Van Den Ende>moves S to north or back to do
temporary deployments to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/614-2
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<v Martijn Van Den Ende>characterise local seismicity
and and cross off properties.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/638-0
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<v Martijn Van Den Ende>And off the data that are being
generated in this project are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/638-1
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<v Martijn Van Den Ende>transferred to France daily with
a sort of a daily</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/638-2
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<v Martijn Van Den Ende>synchronization procedure.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/658-0
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<v Martijn Van Den Ende>We acquire the data at a special
sampling rates of about 15</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/658-1
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<v Martijn Van Den Ende>metres and a temporal sampling
rate of 62 Hertz.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/697-0
00:05:06.293 --> 00:05:10.797
<v Martijn Van Den Ende>So if you then work out the
maths, that amounts to about 300</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/697-1
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<v Martijn Van Den Ende>gigabytes of data per day, or
about half a petabytes of data</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/697-2
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<v Martijn Van Den Ende>over the periods of five years.
And so for this, we have plenty</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/697-3
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<v Martijn Van Den Ende>of storage and processing
capacities at zero by zero to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/697-4
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<v Martijn Van Den Ende>deal.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/700-0
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<v Martijn Van Den Ende>With the data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/730-0
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<v Martijn Van Den Ende>But on top of the daily
transfers that's transferred the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/730-1
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<v Martijn Van Den Ende>roll data to France, we also are
experimenting with sort of live</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/730-2
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<v Martijn Van Den Ende>transfer of data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/757-0
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<v Martijn Van Den Ende>So for this we have set up a
live stream on YouTube, which</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/757-1
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<v Martijn Van Den Ende>unfortunately doesn't work right
now, but hopefully in the near</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/757-2
00:05:44.939 --> 00:05:48.849
<v Martijn Van Den Ende>future it will work again. But
in our office we have actually a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/757-3
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<v Martijn Van Den Ende>screen that shows the data
coming in real time.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/765-0
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<v Martijn Van Den Ende>So here we have an earthquake
and Marie probably presenting.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/773-0
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<v Martijn Van Den Ende>The the data coming in in real
time.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/797-0
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<v Martijn Van Den Ende>Now, the reason why we're doing
this experimentation with the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/797-1
00:06:04.561 --> 00:06:08.714
<v Martijn Van Den Ende>live data transfer is of course
to work on the topic of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/797-2
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<v Martijn Van Den Ende>earthquake really warning.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/810-0
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<v Martijn Van Den Ende>And there are lots of advantages
of using DAS for earthquake</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/810-1
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<v Martijn Van Den Ende>early warning.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/841-0
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<v Martijn Van Den Ende>First of all, we can use DAS to
complements sometimes very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/841-1
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<v Martijn Van Den Ende>sparse coverage of seismometers.
So particularly in the northern</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/841-2
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<v Martijn Van Den Ende>parts of the region where we're
working, we have very few.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/865-0
00:06:31.663 --> 00:06:36.491
<v Martijn Van Den Ende>Land stations and so the special
coverage is very sparse and in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/865-1
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<v Martijn Van Den Ende>addition to that we get offshore
instrumentation.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/893-0
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<v Martijn Van Den Ende>So we are closer to the trench
and closer to the seasick</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/893-1
00:06:44.162 --> 00:06:48.130
<v Martijn Van Den Ende>source. We can use existing
infrastructures because we're</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/893-2
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<v Martijn Van Den Ende>using dark fibre here, so we do
not have any deployment and and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/893-3
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<v Martijn Van Den Ende>maintenance costs related to
that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/907-0
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<v Martijn Van Den Ende>And lastly, the acquisition and
processing of the data takes</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/907-1
00:07:00.924 --> 00:07:01.583
<v Martijn Van Den Ende>place in.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/917-0
00:07:02.103 --> 00:07:03.743
<v Martijn Van Den Ende>And earthquake proof
environment.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/934-0
00:07:04.063 --> 00:07:08.166
<v Martijn Van Den Ende>The interrogators are placed in
server rooms that serve as</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/934-1
00:07:08.166 --> 00:07:11.783
<v Martijn Van Den Ende>central hubs for communication
in case of disaster.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/949-0
00:07:12.303 --> 00:07:16.554
<v Martijn Van Den Ende>So they are really designed to
withstand even the strongest of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/949-1
00:07:16.554 --> 00:07:20.063
<v Martijn Van Den Ende>earthquakes and be operational
during those events.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/975-0
00:07:21.623 --> 00:07:26.043
<v Martijn Van Den Ende>So after setting up the
interrogators last year, we were</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/975-1
00:07:26.043 --> 00:07:30.540
<v Martijn Van Den Ende>sort of hoping between quotes
for a magnitude 6 or larger</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/975-2
00:07:30.540 --> 00:07:34.263
<v Martijn Van Den Ende>earthquake to occur within a
five years period.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1004-0
00:07:35.803 --> 00:07:39.799
<v Martijn Van Den Ende>And so two months later, our
prayers were heard and a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1004-1
00:07:39.799 --> 00:07:43.869
<v Martijn Van Den Ende>magnitude 6.6 earthquake
occurred right at the edge of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1004-2
00:07:43.869 --> 00:07:47.643
<v Martijn Van Den Ende>one of the three cables that we
are instrumenting.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1008-0
00:07:48.483 --> 00:07:51.043
<v Martijn Van Den Ende>So here we have the three
cables.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1015-0
00:07:51.043 --> 00:07:53.963
<v Martijn Van Den Ende>That's that we are that are
located offshore.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1029-0
00:07:54.683 --> 00:07:57.472
<v Martijn Van Den Ende>Earthquake was here in the
north, and so we have this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1029-1
00:07:57.472 --> 00:08:00.003
<v Martijn Van Den Ende>beautiful propagation of the
seismic waves from.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1039-0
00:08:00.863 --> 00:08:04.724
<v Martijn Van Den Ende>North to South here on the
slides, we have N on the left</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1039-1
00:08:04.724 --> 00:08:05.063
<v Martijn Van Den Ende>side.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1044-0
00:08:05.593 --> 00:08:09.313
<v Martijn Van Den Ende>And South on the right and time
is is moving up.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1075-0
00:08:10.863 --> 00:08:15.103
<v Martijn Van Den Ende>And so this look very promising
and this this look like</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1075-1
00:08:15.103 --> 00:08:19.571
<v Martijn Van Den Ende>fantastic data to try early
warning algorithms etcetera on</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1075-2
00:08:19.571 --> 00:08:24.039
<v Martijn Van Den Ende>and some of the data looked
really nice, but unfortunately</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1075-3
00:08:24.039 --> 00:08:26.463
<v Martijn Van Den Ende>most of the data look like this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1082-0
00:08:28.143 --> 00:08:29.943
<v Martijn Van Den Ende>So clearly here something is
wrong.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1088-0
00:08:30.143 --> 00:08:32.863
<v Martijn Van Den Ende>The amplitudes are clips and.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1090-0
00:08:34.423 --> 00:08:34.463
<v Martijn Van Den Ende>This.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1102-0
00:08:35.273 --> 00:08:38.473
<v Martijn Van Den Ende>Prompted us to ask a couple of
questions on OK.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1114-0
00:08:38.473 --> 00:08:42.473
<v Martijn Van Den Ende>How feasible is it to use DAS
for earthquake warning?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1142-0
00:08:44.063 --> 00:08:47.613
<v Martijn Van Den Ende>And so some of the main
questions that we had was well,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1142-1
00:08:47.613 --> 00:08:51.608
<v Martijn Van Den Ende>why are these DAS measurements,
clips or saturated as we as we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1142-2
00:08:51.608 --> 00:08:52.623
<v Martijn Van Den Ende>tend to call it?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1152-0
00:08:53.423 --> 00:08:57.646
<v Martijn Van Den Ende>And what is the big round
displacement or velocity or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1152-1
00:08:57.646 --> 00:08:58.663
<v Martijn Van Den Ende>acceleration?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1168-0
00:09:00.383 --> 00:09:03.728
<v Martijn Van Den Ende>That that triggers this
saturation or other words, what</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1168-1
00:09:03.728 --> 00:09:04.863
<v Martijn Van Den Ende>is the maximum bgd.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1195-0
00:09:05.783 --> 00:09:11.254
<v Martijn Van Den Ende>HGV PGA that we can measure with
us and be more precisely what is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1195-1
00:09:11.254 --> 00:09:15.813
<v Martijn Van Den Ende>the maximum magnitude of an
event that we can reliably</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1195-2
00:09:15.813 --> 00:09:17.223
<v Martijn Van Den Ende>measure with DAS?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1230-0
00:09:19.183 --> 00:09:22.930
<v Martijn Van Den Ende>So to answer the first question,
that's actually relatively</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1230-1
00:09:22.930 --> 00:09:26.739
<v Martijn Van Den Ende>straightforward. If you look at
the measurement principle of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1230-2
00:09:26.739 --> 00:09:30.611
<v Martijn Van Den Ende>DAS, what does measures is the
phase of of light or the phase</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1230-3
00:09:30.611 --> 00:09:34.358
<v Martijn Van Den Ende>difference between consecutive
processes of lights that are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1230-4
00:09:34.358 --> 00:09:34.983
<v Martijn Van Den Ende>sent down.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1259-0
00:09:35.753 --> 00:09:39.572
<v Martijn Van Den Ende>An optical fiber and the
relation between the face that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1259-1
00:09:39.572 --> 00:09:43.528
<v Martijn Van Den Ende>you measure and the sort of
length of the trajectory that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1259-2
00:09:43.528 --> 00:09:46.393
<v Martijn Van Den Ende>the light follows is a simple
linear one.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1279-0
00:09:46.393 --> 00:09:51.377
<v Martijn Van Den Ende>So here on the left we have the
phase diodes by Phi. The</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1279-1
00:09:51.377 --> 00:09:55.313
<v Martijn Van Den Ende>distance of the light travels
here is D and.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1299-0
00:09:56.943 --> 00:10:01.103
<v Martijn Van Den Ende>The the proportionality constant
here in the middle contains the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1299-1
00:10:01.103 --> 00:10:05.007
<v Martijn Van Den Ende>refractive index photo as the
coefficient and the wavelength</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1299-2
00:10:05.007 --> 00:10:05.583
<v Martijn Van Den Ende>of light.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1318-0
00:10:07.033 --> 00:10:11.666
<v Martijn Van Den Ende>And because there's a linear
relationship, we can split this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1318-1
00:10:11.666 --> 00:10:14.553
<v Martijn Van Den Ende>in a reference phase measurement
and.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1329-0
00:10:16.263 --> 00:10:19.303
<v Martijn Van Den Ende>A deviation or a change in the
length of the trajectory.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1336-0
00:10:21.103 --> 00:10:23.303
<v Martijn Van Den Ende>Now normally we don't want to
deal with this reference.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1373-0
00:10:25.263 --> 00:10:29.283
<v Martijn Van Den Ende>Phase so we can get rid of that
by time differentiation and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1373-1
00:10:29.283 --> 00:10:32.901
<v Martijn Van Den Ende>likewise we want our
measurements to be local, so not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1373-2
00:10:32.901 --> 00:10:36.921
<v Martijn Van Den Ende>affected by everything that
happens before in the cable and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1373-3
00:10:36.921 --> 00:10:38.463
<v Martijn Van Den Ende>we can achieve that by.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1415-0
00:10:39.223 --> 00:10:43.229
<v Martijn Van Den Ende>Differentiating this
relationship in space, and so</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1415-1
00:10:43.229 --> 00:10:48.021
<v Martijn Van Den Ende>typically what does instrument
records, is this quantity the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1415-2
00:10:48.021 --> 00:10:52.656
<v Martijn Van Den Ende>gradient of the phase rate,
which is still proportional to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1415-3
00:10:52.656 --> 00:10:57.447
<v Martijn Van Den Ende>the change in the length of the
cable, and so in a way it is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1415-4
00:10:57.447 --> 00:11:00.983
<v Martijn Van Den Ende>proportional more or less to the
to the STR.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1417-0
00:11:00.983 --> 00:11:01.103
<v Martijn Van Den Ende>Rate.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1456-0
00:11:04.363 --> 00:11:08.885
<v Martijn Van Den Ende>Any facial measurement is
periodic around ±π, so as a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1456-1
00:11:08.885 --> 00:11:13.911
<v Martijn Van Den Ende>result this quantity that we are
recording is bounded by by</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1456-2
00:11:13.911 --> 00:11:19.271
<v Martijn Van Den Ende>divided by Delta T, Delta X and
here Delta T is the the rate at</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1456-3
00:11:19.271 --> 00:11:22.203
<v Martijn Van Den Ende>which you are requiring your
data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1465-0
00:11:22.203 --> 00:11:26.523
<v Martijn Van Den Ende>So the sampling rate and delta X
is the spatial sampling.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1476-0
00:11:28.583 --> 00:11:32.863
<v Martijn Van Den Ende>And so if we now use this, this
sort of upper bound.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1486-0
00:11:33.763 --> 00:11:36.083
<v Martijn Van Den Ende>Plug it back into the equation
as you had on a previous slide.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1499-0
00:11:36.083 --> 00:11:39.658
<v Martijn Van Den Ende>Then this gives us that we get
the maximum strain rate that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1499-1
00:11:39.658 --> 00:11:40.283
<v Martijn Van Den Ende>can record.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1516-0
00:11:41.823 --> 00:11:45.629
<v Martijn Van Den Ende>Is is given by this relationship
which contains this something</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1516-1
00:11:45.629 --> 00:11:47.503
<v Martijn Van Den Ende>rate and and special something.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1533-0
00:11:49.873 --> 00:11:53.223
<v Martijn Van Den Ende>And if we plug in some
reasonable numbers for the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1533-1
00:11:53.223 --> 00:11:57.444
<v Martijn Van Den Ende>wavelength of light and these
two parameters together of order</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1533-2
00:11:57.444 --> 00:11:57.713
<v Martijn Van Den Ende>one.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1535-0
00:11:59.263 --> 00:11:59.303
<v Martijn Van Den Ende>A.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1550-0
00:11:59.303 --> 00:12:02.279
<v Martijn Van Den Ende>Times sampling rate of about
kilohertz and a special sampling</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1550-1
00:12:02.279 --> 00:12:02.903
<v Martijn Van Den Ende>of 10 meters.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1558-0
00:12:03.303 --> 00:12:06.771
<v Martijn Van Den Ende>This gives us a upper bound on
the strain rate that we can</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1558-1
00:12:06.771 --> 00:12:07.183
<v Martijn Van Den Ende>record.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1572-0
00:12:08.783 --> 00:12:12.723
<v Martijn Van Den Ende>Of around 40 micro strain per
second. So micrometer per meter</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1572-1
00:12:12.723 --> 00:12:13.423
<v Martijn Van Den Ende>per second.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1583-0
00:12:15.143 --> 00:12:18.171
<v Martijn Van Den Ende>And if we then compare that with
our actual measurements, we see</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1583-1
00:12:18.171 --> 00:12:19.383
<v Martijn Van Den Ende>that it works really well.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1591-0
00:12:20.523 --> 00:12:23.523
<v Martijn Van Den Ende>So here the values here on the
vertical axis.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1612-0
00:12:25.303 --> 00:12:27.933
<v Martijn Van Den Ende>Denote the strain rate but with
lower values because the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1612-1
00:12:27.933 --> 00:12:30.656
<v Martijn Van Den Ende>acquisition settings were a bit
different than what I just</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1612-2
00:12:30.656 --> 00:12:31.903
<v Martijn Van Den Ende>plugged into as an example.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1634-0
00:12:32.583 --> 00:12:36.387
<v Martijn Van Den Ende>But here what we have is actual
data from the swell, so the the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1634-1
00:12:36.387 --> 00:12:38.943
<v Martijn Van Den Ende>ocean waves that are passing by
the cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1666-0
00:12:39.223 --> 00:12:43.130
<v Martijn Van Den Ende>This is nice long period signal
and we can see it as soon as it</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1666-1
00:12:43.130 --> 00:12:47.037
<v Martijn Van Den Ende>hits this dynamic range and then
upper limit it's kind of flips</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1666-2
00:12:47.037 --> 00:12:50.823
<v Martijn Van Den Ende>to the other side and continues
and then goes back and so on.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1668-0
00:12:50.823 --> 00:12:51.943
<v Martijn Van Den Ende>So this is the typical.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1681-0
00:12:53.843 --> 00:12:57.865
<v Martijn Van Den Ende>Type of saturation that we're
getting with with gas data on</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1681-1
00:12:57.865 --> 00:12:58.603
<v Martijn Van Den Ende>the bottom.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1724-0
00:12:58.603 --> 00:13:01.596
<v Martijn Van Den Ende>Here we have a vibrating
segment, so a segment of of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1724-1
00:13:01.596 --> 00:13:05.154
<v Martijn Van Den Ende>cable that is hanging freely in
the water column and vibrates.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1724-2
00:13:05.154 --> 00:13:08.373
<v Martijn Van Den Ende>And these vibrations have
increasing amplitude and so as</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1724-3
00:13:08.373 --> 00:13:11.649
<v Martijn Van Den Ende>soon as these amplitudes hits
the dynamic range, we start</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1724-4
00:13:11.649 --> 00:13:13.683
<v Martijn Van Den Ende>getting very complicated
behaviour.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1739-0
00:13:16.473 --> 00:13:21.574
<v Martijn Van Den Ende>Now, what is this number of 40
microstrane per second really</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1739-1
00:13:21.574 --> 00:13:21.993
<v Martijn Van Den Ende>mean?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1769-0
00:13:22.193 --> 00:13:26.164
<v Martijn Van Den Ende>And because usually work with
particle motions like P DRAM</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1769-1
00:13:26.164 --> 00:13:29.933
<v Martijn Van Den Ende>displacement or P ground
acceleration, so we can make a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1769-2
00:13:29.933 --> 00:13:33.433
<v Martijn Van Den Ende>conversion using a simple
monochromatic oscillator.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1788-0
00:13:34.153 --> 00:13:39.608
<v Martijn Van Den Ende>So if we have sort of a cosine
like wave form with a frequency</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1788-1
00:13:39.608 --> 00:13:42.033
<v Martijn Van Den Ende>F and a propagation speed C.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1795-0
00:13:42.903 --> 00:13:45.863
<v Martijn Van Den Ende>And the maximum peak ground
displacement a.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1818-0
00:13:46.973 --> 00:13:51.593
<v Martijn Van Den Ende>Then if we differentiate this
expression once in time, once in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1818-1
00:13:51.593 --> 00:13:55.919
<v Martijn Van Den Ende>space, then we getting the
strain rate that corresponds to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1818-2
00:13:55.919 --> 00:13:57.093
<v Martijn Van Den Ende>that oscillator.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1826-0
00:13:57.853 --> 00:14:01.797
<v Martijn Van Den Ende>And so if we then plug this into
the criterion for the dynamic</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1826-1
00:14:01.797 --> 00:14:02.173
<v Martijn Van Den Ende>range.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1864-0
00:14:03.743 --> 00:14:07.513
<v Martijn Van Den Ende>Then we get an expression like
this and I'm just split it out</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1864-1
00:14:07.513 --> 00:14:11.283
<v Martijn Van Den Ende>into three components, one that
is related to the wave field,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1864-2
00:14:11.283 --> 00:14:14.932
<v Martijn Van Den Ende>one that is intrinsic to the
fibre and one it is related to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1864-3
00:14:14.932 --> 00:14:17.183
<v Martijn Van Den Ende>the acquisition or your
instruments.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-0
00:14:18.253 --> 00:14:22.871
<v Martijn Van Den Ende>And so if we again plug in some
realistic numbers for this, we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-1
00:14:22.871 --> 00:14:26.317
<v Martijn Van Den Ende>get a maximum P prime
displacement of about 25</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-2
00:14:26.317 --> 00:14:30.862
<v Martijn Van Den Ende>micrometres, meaning that any P
gram displacement larger than</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-3
00:14:30.862 --> 00:14:34.821
<v Martijn Van Den Ende>that would saturate our
measurements. And so those of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-4
00:14:34.821 --> 00:14:38.926
<v Martijn Van Den Ende>you working with earthquake
warning will recognize that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1907-5
00:14:38.926 --> 00:14:39.293
<v Martijn Van Den Ende>this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1920-0
00:14:39.293 --> 00:14:42.467
<v Martijn Van Den Ende>Is a very small number and this
would correspond with a very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1920-1
00:14:42.467 --> 00:14:43.613
<v Martijn Van Den Ende>small magnitude event.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1922-0
00:14:44.543 --> 00:14:45.303
<v Martijn Van Den Ende>That is close by.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1934-0
00:14:48.593 --> 00:14:51.513
<v Martijn Van Den Ende>Now, earthquakes are of course
not monochromatic.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1941-0
00:14:51.513 --> 00:14:56.608
<v Martijn Van Den Ende>They are broadband and the
threshold for saturation depends</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1941-1
00:14:56.608 --> 00:14:57.713
<v Martijn Van Den Ende>on frequency.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1956-0
00:14:59.263 --> 00:15:02.100
<v Martijn Van Den Ende>Particularly because of this
conversion between the strain</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1956-1
00:15:02.100 --> 00:15:03.303
<v Martijn Van Den Ende>rates to particle motion.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1988-0
00:15:04.983 --> 00:15:08.282
<v Martijn Van Den Ende>So maybe you know this
relationship is not entirely</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1988-1
00:15:08.282 --> 00:15:12.279
<v Martijn Van Den Ende>accurate for earthquakes, and so
one of the objectives that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1988-2
00:15:12.279 --> 00:15:16.023
<v Martijn Van Den Ende>had was to come up with a
saturation threshold in terms of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1988-3
00:15:16.023 --> 00:15:17.863
<v Martijn Van Den Ende>earthquake source parameters.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/1999-0
00:15:19.483 --> 00:15:22.523
<v Martijn Van Den Ende>And I will spare you the
details, but this is the result.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2009-0
00:15:23.083 --> 00:15:27.331
<v Martijn Van Den Ende>So this looks very long and
complicated, but I'll just break</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2009-1
00:15:27.331 --> 00:15:29.003
<v Martijn Van Den Ende>it down into small bits.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2029-0
00:15:31.143 --> 00:15:34.983
<v Martijn Van Den Ende>So on the left here we have the
magnitude of an earthquake that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2029-1
00:15:34.983 --> 00:15:37.143
<v Martijn Van Den Ende>would cause saturation of our
data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2042-0
00:15:38.693 --> 00:15:41.905
<v Martijn Van Den Ende>And the components that we have
here in this in this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2042-1
00:15:41.905 --> 00:15:42.693
<v Martijn Van Den Ende>relationship.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2057-0
00:15:44.303 --> 00:15:46.943
<v Martijn Van Den Ende>The notes parameters relating to
the acquisition.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2076-0
00:15:47.063 --> 00:15:51.643
<v Martijn Van Den Ende>So the things like the time
something rate and the special</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2076-1
00:15:51.643 --> 00:15:56.223
<v Martijn Van Den Ende>sampling going here, seismic
source parameters go in here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2082-0
00:15:56.223 --> 00:15:58.623
<v Martijn Van Den Ende>So we have a stress drop and
radiation pattern.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2103-0
00:16:00.263 --> 00:16:03.995
<v Martijn Van Den Ende>We have some parameters related
to the propagation in the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2103-1
00:16:03.995 --> 00:16:08.049
<v Martijn Van Den Ende>medium, so we have this quality
factor for attenuation and the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2103-2
00:16:08.049 --> 00:16:09.143
<v Martijn Van Den Ende>shear wave speed.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2112-0
00:16:09.953 --> 00:16:12.818
<v Martijn Van Den Ende>And finally, we have here
component related to the Hyper</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2112-1
00:16:12.818 --> 00:16:13.673
<v Martijn Van Den Ende>central distance.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2159-0
00:16:15.223 --> 00:16:19.698
<v Martijn Van Den Ende>So in most cases all the 1st 3
components are simply fixed or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2159-1
00:16:19.698 --> 00:16:23.524
<v Martijn Van Den Ende>well approximated by a
representative number, and so</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2159-2
00:16:23.524 --> 00:16:27.567
<v Martijn Van Den Ende>this this equation simply is a
relationship between the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2159-3
00:16:27.567 --> 00:16:31.826
<v Martijn Van Den Ende>magnitude that would cause
saturation in our dash data and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2159-4
00:16:31.826 --> 00:16:33.703
<v Martijn Van Den Ende>the hypercentral distance.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2167-0
00:16:35.383 --> 00:16:37.943
<v Martijn Van Den Ende>And this relationship I plotted
over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2216-0
00:16:38.743 --> 00:16:43.337
<v Martijn Van Den Ende>So in this very busy figure we
have on the horizontal axis the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2216-1
00:16:43.337 --> 00:16:47.421
<v Martijn Van Den Ende>hypercentral distance in
kilometers and on the vertical</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2216-2
00:16:47.421 --> 00:16:51.579
<v Martijn Van Den Ende>axis the magnitudes of the
events and this long equation</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2216-3
00:16:51.579 --> 00:16:56.173
<v Martijn Van Den Ende>that I had on a previous slide
is given by this solid or this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2216-4
00:16:56.173 --> 00:16:58.143
<v Martijn Van Den Ende>This dashed line over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2226-0
00:16:59.103 --> 00:17:03.543
<v Martijn Van Den Ende>So any earthquake, it has a
magnitude that falls above.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2240-0
00:17:04.343 --> 00:17:08.268
<v Martijn Van Den Ende>This this line would call
saturation and any earthquake</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2240-1
00:17:08.268 --> 00:17:11.143
<v Martijn Van Den Ende>this either far away or has a
magnitude.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2251-0
00:17:12.303 --> 00:17:16.648
<v Martijn Van Den Ende>Plots within this this space
below the Black line would not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2251-1
00:17:16.648 --> 00:17:17.663
<v Martijn Van Den Ende>saturate data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2279-0
00:17:19.223 --> 00:17:22.504
<v Martijn Van Den Ende>Then the colours that you see
here are actual measurements,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2279-1
00:17:22.504 --> 00:17:25.513
<v Martijn Van Den Ende>because we have lots of
earthquakes that were recorded</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2279-2
00:17:25.513 --> 00:17:28.303
<v Martijn Van Den Ende>at various hyper central
distances and magnitudes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2311-0
00:17:28.503 --> 00:17:33.161
<v Martijn Van Den Ende>So for each of these events, I
took the catalogue magnitude and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2311-1
00:17:33.161 --> 00:17:37.965
<v Martijn Van Den Ende>and location and then determined
whether a given task measurement</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2311-2
00:17:37.965 --> 00:17:41.023
<v Martijn Van Den Ende>was saturated or not for this
earthquake.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2317-0
00:17:41.863 --> 00:17:42.703
<v Martijn Van Den Ende>Was not saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2327-0
00:17:42.703 --> 00:17:47.172
<v Martijn Van Den Ende>I plotted it in green if it was
saturated, I plotted it in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2327-1
00:17:47.172 --> 00:17:47.703
<v Martijn Van Den Ende>orange.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2353-0
00:17:49.263 --> 00:17:53.177
<v Martijn Van Den Ende>And so you can see that this
criterion that was on the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2353-1
00:17:53.177 --> 00:17:57.377
<v Martijn Van Den Ende>previous slide more or less
device the data into saturated</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2353-2
00:17:57.377 --> 00:17:58.943
<v Martijn Van Den Ende>and and non saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2382-0
00:18:00.783 --> 00:18:04.553
<v Martijn Van Den Ende>Recordings and this is perhaps a
bit better to see if we just</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2382-1
00:18:04.553 --> 00:18:08.263
<v Martijn Van Den Ende>rescale the horizontal axis or
transform it to a logarithmic</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2382-2
00:18:08.263 --> 00:18:11.912
<v Martijn Van Den Ende>scaling, and then we can see
nicely that both are large and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2382-3
00:18:11.912 --> 00:18:12.703
<v Martijn Van Den Ende>small events.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2389-0
00:18:14.193 --> 00:18:16.513
<v Martijn Van Den Ende>All the events that plot above
these lines.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2402-0
00:18:18.063 --> 00:18:20.894
<v Martijn Van Den Ende>They are saturated and below the
lines they're mostly not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2402-1
00:18:20.894 --> 00:18:21.383
<v Martijn Van Den Ende>saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2443-0
00:18:23.143 --> 00:18:26.852
<v Martijn Van Den Ende>And now if you look a bit more
closely at the range of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2443-1
00:18:26.852 --> 00:18:31.101
<v Martijn Van Den Ende>distances that are relevant for
earthquake related warning. So</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2443-2
00:18:31.101 --> 00:18:35.215
<v Martijn Van Den Ende>let's say that we take a high
percentile distance of, say 50</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2443-3
00:18:35.215 --> 00:18:39.464
<v Martijn Van Den Ende>kilometers, then you will see
that saturation is predicted and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2443-4
00:18:39.464 --> 00:18:41.623
<v Martijn Van Den Ende>also observed to occur for magn.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2445-0
00:18:41.623 --> 00:18:42.743
<v Martijn Van Den Ende>As small as three.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2484-0
00:18:44.623 --> 00:18:49.096
<v Martijn Van Den Ende>And so, of course it is really
bad news that even for very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2484-1
00:18:49.096 --> 00:18:53.872
<v Martijn Van Den Ende>small magnitude earthquakes, we
already have saturation of our</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2484-2
00:18:53.872 --> 00:18:58.800
<v Martijn Van Den Ende>DAS data and what we would like
to do is to record correctly the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2484-3
00:18:58.800 --> 00:19:03.576
<v Martijn Van Den Ende>wave forms of earthquakes up to
magnitude 6 or even larger. So</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2484-4
00:19:03.576 --> 00:19:04.183
<v Martijn Van Den Ende>we have.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2499-0
00:19:04.183 --> 00:19:07.816
<v Martijn Van Den Ende>This gap of orders of magnitude
in the the dynamic range that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2499-1
00:19:07.816 --> 00:19:08.823
<v Martijn Van Den Ende>are still missing.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2507-0
00:19:11.693 --> 00:19:15.093
<v Martijn Van Den Ende>O could we potentially fix this
in a way?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2527-0
00:19:16.663 --> 00:19:20.212
<v Martijn Van Den Ende>Well, first of all, you have to
realise that when saturation</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2527-1
00:19:20.212 --> 00:19:23.703
<v Martijn Van Den Ende>starts, most of the original
information is still retained.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2570-0
00:19:24.463 --> 00:19:28.779
<v Martijn Van Den Ende>So here again we have the
example of the the swell, even</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2570-1
00:19:28.779 --> 00:19:33.474
<v Martijn Van Den Ende>though it starts to saturate the
recordings, we can recognise</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2570-2
00:19:33.474 --> 00:19:37.866
<v Martijn Van Den Ende>most of the swell in in in the
recordings here and if you</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2570-3
00:19:37.866 --> 00:19:42.183
<v Martijn Van Den Ende>calculate the spectrum you will
more or less obtain the.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2575-0
00:19:42.863 --> 00:19:44.903
<v Martijn Van Den Ende>Spectrum for this type of
signal.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2595-0
00:19:46.873 --> 00:19:51.102
<v Martijn Van Den Ende>And so, in a way, we could maybe
try some spectral analysis and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2595-1
00:19:51.102 --> 00:19:55.067
<v Martijn Van Den Ende>see if we can still extract
useful information relevant for</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2595-2
00:19:55.067 --> 00:19:55.993
<v Martijn Van Den Ende>early warning.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2605-0
00:19:58.413 --> 00:20:01.373
<v Martijn Van Den Ende>So here is a synthetic example
of that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2629-0
00:20:01.573 --> 00:20:05.363
<v Martijn Van Den Ende>So this is a simple spectrum on
the horizontal axis I have a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2629-1
00:20:05.363 --> 00:20:07.973
<v Martijn Van Den Ende>frequency on the vertical axis I
have oh.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2656-0
00:20:08.063 --> 00:20:12.264
<v Martijn Van Den Ende>This is not spectral density,
but the spectral amplitude, and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2656-1
00:20:12.264 --> 00:20:16.602
<v Martijn Van Den Ende>this is for. So what I do here
is I take a a waveform generated</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2656-2
00:20:16.602 --> 00:20:18.703
<v Martijn Van Den Ende>from a standard prune spectrum.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2703-0
00:20:18.703 --> 00:20:23.342
<v Martijn Van Den Ende>So the spectrum is given in
black in the background and then</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2703-1
00:20:23.342 --> 00:20:28.058
<v Martijn Van Den Ende>I scale up the amplitude beyond
the dynamic range and sort of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2703-2
00:20:28.058 --> 00:20:33.078
<v Martijn Van Den Ende>rescale or wrap the signal as if
we are recording it with DAS and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2703-3
00:20:33.078 --> 00:20:37.642
<v Martijn Van Den Ende>so the spectrum resulting from
that is the orange line over</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2703-4
00:20:37.642 --> 00:20:38.023
<v Martijn Van Den Ende>here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2705-0
00:20:38.303 --> 00:20:38.463
<v Martijn Van Den Ende>4.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2745-0
00:20:39.263 --> 00:20:43.773
<v Martijn Van Den Ende>And so you can see that while
most of the original spectrum is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2745-1
00:20:43.773 --> 00:20:47.998
<v Martijn Van Den Ende>is is retained, there are some
sidelobes that are that are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2745-2
00:20:47.998 --> 00:20:52.366
<v Martijn Van Den Ende>forming and the lower and the
higher frequencies. But if you</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2745-3
00:20:52.366 --> 00:20:56.948
<v Martijn Van Den Ende>were to record a spectrum like
this, you would still be able to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2745-4
00:20:56.948 --> 00:20:58.023
<v Martijn Van Den Ende>recover things.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2754-0
00:20:58.023 --> 00:20:59.903
<v Martijn Van Den Ende>Like the corner frequency for
instance.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2770-0
00:21:01.573 --> 00:21:05.609
<v Martijn Van Den Ende>And if we then gradually
increase this amplitude and then</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2770-1
00:21:05.609 --> 00:21:08.533
<v Martijn Van Den Ende>do the exercise again, you will
see that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2787-0
00:21:09.063 --> 00:21:13.403
<v Martijn Van Den Ende>Actually, more of this energy
around the peak starts to leak</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2787-1
00:21:13.403 --> 00:21:15.183
<v Martijn Van Den Ende>away into the side lobes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2799-0
00:21:15.183 --> 00:21:18.118
<v Martijn Van Den Ende>So the side lobes become more
prominent and the peak, the peak</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2799-1
00:21:18.118 --> 00:21:19.143
<v Martijn Van Den Ende>becomes a bit smaller.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2845-0
00:21:20.693 --> 00:21:24.864
<v Martijn Van Den Ende>And so keep doing this for
higher and higher amplitudes and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2845-1
00:21:24.864 --> 00:21:28.688
<v Martijn Van Den Ende>then you will see that
eventually the spectrum that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2845-2
00:21:28.688 --> 00:21:33.138
<v Martijn Van Den Ende>record becomes pretty much flat,
which would be indicative of a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2845-3
00:21:33.138 --> 00:21:37.449
<v Martijn Van Den Ende>uniform distribution. And so if
you were to record a spectrum</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2845-4
00:21:37.449 --> 00:21:39.813
<v Martijn Van Den Ende>like this, you would not be
able.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2848-0
00:21:39.813 --> 00:21:40.853
<v Martijn Van Den Ende>To recover.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2853-0
00:21:42.123 --> 00:21:43.443
<v Martijn Van Den Ende>Things like the corner
frequency.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2869-0
00:21:46.373 --> 00:21:50.643
<v Martijn Van Den Ende>Another way to look at this is
to look at how close our data</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2869-1
00:21:50.643 --> 00:21:53.093
<v Martijn Van Den Ende>represents a uniform
distribution.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2889-0
00:21:54.053 --> 00:21:58.135
<v Martijn Van Den Ende>So if you just focus on the
bottom left panel over here,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2889-1
00:21:58.135 --> 00:22:01.573
<v Martijn Van Den Ende>here are plotted a cumulative
density function.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2896-0
00:22:01.613 --> 00:22:04.173
<v Martijn Van Den Ende>So essentially sort of the
integral of a histogram.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2908-0
00:22:05.733 --> 00:22:09.493
<v Martijn Van Den Ende>Of the the data skills between
this case minus and plus one.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2917-0
00:22:11.173 --> 00:22:14.369
<v Martijn Van Den Ende>In this representation, a
uniform distribution would</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2917-1
00:22:14.369 --> 00:22:14.973
<v Martijn Van Den Ende>simply be.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2926-0
00:22:15.553 --> 00:22:20.113
<v Martijn Van Den Ende>A straight line, so it is dotted
line over here would be what?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2947-0
00:22:20.113 --> 00:22:24.957
<v Martijn Van Den Ende>The uniform distribution would
give you and initially our data</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2947-1
00:22:24.957 --> 00:22:29.033
<v Martijn Van Den Ende>is more or less sort of Gaussian
in in distribution.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2974-0
00:22:29.033 --> 00:22:33.754
<v Martijn Van Den Ende>So it's kind of gives you this
nice *** shape over here, but as</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2974-1
00:22:33.754 --> 00:22:38.180
<v Martijn Van Den Ende>the amplitude increases, we
gradually get closer and closer</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2974-2
00:22:38.180 --> 00:22:40.393
<v Martijn Van Den Ende>to this to this diagonal line.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2985-0
00:22:41.173 --> 00:22:45.239
<v Martijn Van Den Ende>Indicating that our data become
more and more close to a uniform</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2985-1
00:22:45.239 --> 00:22:46.053
<v Martijn Van Den Ende>distribution.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/2991-0
00:22:46.943 --> 00:22:49.023
<v Martijn Van Den Ende>Losing all useful information.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3005-0
00:22:51.633 --> 00:22:55.299
<v Martijn Van Den Ende>We can actually measure the
distance between our current</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3005-1
00:22:55.299 --> 00:22:57.873
<v Martijn Van Den Ende>data distribution and that of an
ideal.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3009-0
00:22:59.413 --> 00:23:00.533
<v Martijn Van Den Ende>Uniform distribution.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3019-0
00:23:02.213 --> 00:23:04.533
<v Martijn Van Den Ende>The metric for this is given
over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3032-0
00:23:05.093 --> 00:23:08.434
<v Martijn Van Den Ende>I guess it will not make much
sense to you right now, but I</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3032-1
00:23:08.434 --> 00:23:10.773
<v Martijn Van Den Ende>can assure you that it makes
sense to me.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3046-0
00:23:12.693 --> 00:23:17.318
<v Martijn Van Den Ende>And so when we have wave forms
with different degrees of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3046-1
00:23:17.318 --> 00:23:21.133
<v Martijn Van Den Ende>saturation, we can use this
metric to measure.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3056-0
00:23:21.713 --> 00:23:26.153
<v Martijn Van Den Ende>How saturated it is O if the
data are retty.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3059-0
00:23:26.153 --> 00:23:27.393
<v Martijn Van Den Ende>Much not saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3083-0
00:23:27.673 --> 00:23:32.458
<v Martijn Van Den Ende>We have a relatively low metric
of value of the metric and as</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3083-1
00:23:32.458 --> 00:23:36.549
<v Martijn Van Den Ende>the data become more and more
saturated, this metric</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3083-2
00:23:36.549 --> 00:23:37.553
<v Martijn Van Den Ende>approaches 1.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3109-0
00:23:39.093 --> 00:23:43.650
<v Martijn Van Den Ende>And so basically what I just
said is also depicted here is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3109-1
00:23:43.650 --> 00:23:48.053
<v Martijn Van Den Ende>figure where we have the
amplitude by which the waveform</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3109-2
00:23:48.053 --> 00:23:50.293
<v Martijn Van Den Ende>exceeds the dynamic range so.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3133-0
00:23:51.543 --> 00:23:55.694
<v Martijn Van Den Ende>One here indicates dynamic range
and then we get here a factor of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3133-1
00:23:55.694 --> 00:23:59.405
<v Martijn Van Den Ende>10 a factor hundred a factor of
1000 exceeding the dynamic</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3133-2
00:23:59.405 --> 00:23:59.783
<v Martijn Van Den Ende>range.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3165-0
00:24:00.463 --> 00:24:04.781
<v Martijn Van Den Ende>And so if we do that, we can
measure how the saturation</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3165-1
00:24:04.781 --> 00:24:09.562
<v Martijn Van Den Ende>metric changes with increasing
amplitude, and we can see that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3165-2
00:24:09.562 --> 00:24:14.497
<v Martijn Van Den Ende>up to about a factor 10 or maybe
a factor of 20. We could still</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3165-3
00:24:14.497 --> 00:24:15.423
<v Martijn Van Den Ende>distinguish.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3177-0
00:24:16.573 --> 00:24:20.802
<v Martijn Van Den Ende>Based on the saturation metric,
what the original amplitude has</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3177-1
00:24:20.802 --> 00:24:21.133
<v Martijn Van Den Ende>been.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3188-0
00:24:22.233 --> 00:24:25.181
<v Martijn Van Den Ende>So what we do is we just take a
particular waveform that is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3188-1
00:24:25.181 --> 00:24:25.673
<v Martijn Van Den Ende>saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3216-0
00:24:25.913 --> 00:24:29.465
<v Martijn Van Den Ende>We compute the saturation
metric, which could fall</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3216-1
00:24:29.465 --> 00:24:33.854
<v Martijn Van Den Ende>somewhere over here, and then
the corresponding amplitude that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3216-2
00:24:33.854 --> 00:24:38.313
<v Martijn Van Den Ende>causes this kind of saturation
would here be, say, a factor 15.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3233-0
00:24:39.853 --> 00:24:44.312
<v Martijn Van Den Ende>So even though the amplitudes
are saturating, they cannot</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3233-1
00:24:44.312 --> 00:24:46.773
<v Martijn Van Den Ende>increase beyond a certain value.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3250-0
00:24:47.133 --> 00:24:51.125
<v Martijn Van Den Ende>We could still estimate the
original signal amplitudes that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3250-1
00:24:51.125 --> 00:24:54.053
<v Martijn Van Den Ende>have caused a certain degree of
saturation.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3269-0
00:24:54.973 --> 00:25:00.096
<v Martijn Van Den Ende>Up to a factor 20 or so, after
which this metric itself</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3269-1
00:25:00.096 --> 00:25:03.573
<v Martijn Van Den Ende>saturates ironically and and
plateau.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3287-0
00:25:03.573 --> 00:25:08.823
<v Martijn Van Den Ende>So we cannot distinguish whether
the signal is 20 or 100 or 1000</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3287-1
00:25:08.823 --> 00:25:11.813
<v Martijn Van Den Ende>times higher than the dynamic
range.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3312-0
00:25:14.973 --> 00:25:19.109
<v Martijn Van Den Ende>So I kind of want to stop here
talking about the dynamic range</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3312-1
00:25:19.109 --> 00:25:23.377
<v Martijn Van Den Ende>because there is more and let me
just check how much time I have</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3312-2
00:25:23.377 --> 00:25:25.413
<v Martijn Van Den Ende>left. OK. So I still have time.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3341-0
00:25:26.973 --> 00:25:30.920
<v Martijn Van Den Ende>So as an intermediate
conclusion, I just want to know</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3341-1
00:25:30.920 --> 00:25:35.672
<v Martijn Van Den Ende>give you as a take home message
that currently the dynamic range</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3341-2
00:25:35.672 --> 00:25:39.693
<v Martijn Van Den Ende>of DAS is not sufficient for
earthquake early warning.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3353-0
00:25:41.333 --> 00:25:45.344
<v Martijn Van Den Ende>And possibly we can extend this
dynamic range by a factor 10 or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3353-1
00:25:45.344 --> 00:25:45.533
<v Martijn Van Den Ende>20.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3382-0
00:25:46.673 --> 00:25:51.441
<v Martijn Van Den Ende>By analyzing the data in a
different way, but it will not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3382-1
00:25:51.441 --> 00:25:56.046
<v Martijn Van Den Ende>get us up to the level of
recording a magnitude 6 event</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3382-2
00:25:56.046 --> 00:25:59.993
<v Martijn Van Den Ende>faithfully with typical
acquisition parameters.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3436-0
00:26:01.373 --> 00:26:05.984
<v Martijn Van Den Ende>But we could use DAS together
with the online strong motion</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3436-1
00:26:05.984 --> 00:26:10.826
<v Martijn Van Den Ende>sensors to at least expedite a
warning. For instance, we could</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3436-2
00:26:10.826 --> 00:26:15.361
<v Martijn Van Den Ende>consider locating the seismic
event with DAS, which is not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3436-3
00:26:15.361 --> 00:26:19.819
<v Martijn Van Den Ende>affected by by saturation
because the first arrival is is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3436-4
00:26:19.819 --> 00:26:22.433
<v Martijn Van Den Ende>week, and then as soon as the
SE.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3447-0
00:26:22.533 --> 00:26:26.018
<v Martijn Van Den Ende>Waves hits the first strong
motion sensor. We can estimate</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3447-1
00:26:26.018 --> 00:26:27.613
<v Martijn Van Den Ende>the magnitude of the event.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3455-0
00:26:28.393 --> 00:26:31.433
<v Martijn Van Den Ende>With the single sensor from
based on the spectrum.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3470-0
00:26:32.343 --> 00:26:36.755
<v Martijn Van Den Ende>And then we can already send out
an alert, even though only the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3470-1
00:26:36.755 --> 00:26:39.583
<v Martijn Van Den Ende>first online station has been
triggered.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3495-0
00:26:41.083 --> 00:26:44.633
<v Martijn Van Den Ende>And clearly there is a need for
more technological advances,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3495-1
00:26:44.633 --> 00:26:48.009
<v Martijn Van Den Ende>particularly in photonics, to
see if we can increase this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3495-2
00:26:48.009 --> 00:26:50.163
<v Martijn Van Den Ende>dynamic range in one way or
another.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3505-0
00:26:51.993 --> 00:26:54.153
<v Martijn Van Den Ende>All right, now the second thing
I want to talk about.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3538-0
00:26:55.873 --> 00:27:00.045
<v Martijn Van Den Ende>Is local back projection, so for
not necessarily earthquake</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3538-1
00:27:00.045 --> 00:27:03.662
<v Martijn Van Den Ende>related warning, but
particularly for tsunami early</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3538-2
00:27:03.662 --> 00:27:07.626
<v Martijn Van Den Ende>warning, we need to characterize
the rupture in terms of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3538-3
00:27:07.626 --> 00:27:11.313
<v Martijn Van Den Ende>magnitude and whether it has a
surface break or not.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3544-0
00:27:11.853 --> 00:27:13.413
<v Martijn Van Den Ende>And the rupture area and things
like that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3562-0
00:27:14.913 --> 00:27:19.023
<v Martijn Van Den Ende>And for these kind of things, we
don't want to wait for Taylor</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3562-1
00:27:19.023 --> 00:27:21.633
<v Martijn Van Den Ende>seismic W phases to estimate
magnitude.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3586-0
00:27:23.473 --> 00:27:28.324
<v Martijn Van Den Ende>So instead things we can do is
do for instance a rapid finite</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3586-1
00:27:28.324 --> 00:27:33.097
<v Martijn Van Den Ende>fault inversion using the local
xorometer network to get the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3586-2
00:27:33.097 --> 00:27:34.193
<v Martijn Van Den Ende>finer details.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3597-0
00:27:36.073 --> 00:27:41.129
<v Martijn Van Den Ende>Or as fine as possible of the
rupture. But a second solution</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3597-1
00:27:41.129 --> 00:27:41.793
<v Martijn Van Den Ende>to this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3607-0
00:27:42.383 --> 00:27:46.303
<v Martijn Van Den Ende>To this challenge is using local
arrays to do back projection.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3640-0
00:27:47.343 --> 00:27:51.338
<v Martijn Van Den Ende>So here it is nicely sort of
drawn schematically where we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3640-1
00:27:51.338 --> 00:27:55.196
<v Martijn Van Den Ende>have an earthquake that is
recorded by multiple seismic</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3640-2
00:27:55.196 --> 00:27:59.123
<v Martijn Van Den Ende>arrays that are then used to
back project the signal and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3640-3
00:27:59.123 --> 00:28:02.223
<v Martijn Van Den Ende>essentially track the rupture as
it evolves.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3673-0
00:28:04.743 --> 00:28:08.931
<v Martijn Van Den Ende>And I guess that's that's many
of you are familiar with data</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3673-1
00:28:08.931 --> 00:28:12.845
<v Martijn Van Den Ende>seismic back projection where
you take Continental scale</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3673-2
00:28:12.845 --> 00:28:16.759
<v Martijn Van Den Ende>arrays to zoom in and look at
relatively large magnitude</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3673-3
00:28:16.759 --> 00:28:17.583
<v Martijn Van Den Ende>earthquakes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3687-0
00:28:18.143 --> 00:28:22.244
<v Martijn Van Den Ende>And this has been very
successful in in characterising</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3687-1
00:28:22.244 --> 00:28:24.183
<v Martijn Van Den Ende>these very large ruptures.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3696-0
00:28:24.503 --> 00:28:28.525
<v Martijn Van Den Ende>So here's an example from Peru
where we could very nicely track</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3696-1
00:28:28.525 --> 00:28:29.343
<v Martijn Van Den Ende>this rupture.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3711-0
00:28:30.153 --> 00:28:33.851
<v Martijn Van Den Ende>Propagating in a particular
direction, then also identify a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3711-1
00:28:33.851 --> 00:28:35.393
<v Martijn Van Den Ende>back propagating rupture.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3714-0
00:28:35.903 --> 00:28:36.703
<v Martijn Van Den Ende>At the same time.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-0
00:28:39.473 --> 00:28:43.704
<v Martijn Van Den Ende>We can also do this at the local
scale. What's very nice about</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-1
00:28:43.704 --> 00:28:47.332
<v Martijn Van Den Ende>that is that local back
projection should have a much</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-2
00:28:47.332 --> 00:28:51.362
<v Martijn Van Den Ende>higher resolution because you're
much closer to the seasick</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-3
00:28:51.362 --> 00:28:54.855
<v Martijn Van Den Ende>source. But these local
waveforms tend to be rather</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-4
00:28:54.855 --> 00:28:58.617
<v Martijn Van Den Ende>messy. Having lots of local
scattering and simultaneous</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3756-5
00:28:58.617 --> 00:28:58.953
<v Martijn Van Den Ende>Arri.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3761-0
00:28:59.153 --> 00:28:59.993
<v Martijn Van Den Ende>Or phases.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3773-0
00:29:00.633 --> 00:29:03.967
<v Martijn Van Den Ende>And so it is not very likely
that waveform coherence that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3773-1
00:29:03.967 --> 00:29:05.553
<v Martijn Van Den Ende>need for the back projection.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3780-0
00:29:06.353 --> 00:29:08.793
<v Martijn Van Den Ende>Persists across the scale of an
entire array.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3806-0
00:29:09.923 --> 00:29:14.009
<v Martijn Van Den Ende>So instead we would have to
break up the array into locally</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3806-1
00:29:14.009 --> 00:29:17.960
<v Martijn Van Den Ende>coherent sub arrays and then
combine the results of these</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3806-2
00:29:17.960 --> 00:29:21.843
<v Martijn Van Den Ende>smaller arrays to really focus
on the earthquake source.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3819-0
00:29:23.393 --> 00:29:26.313
<v Martijn Van Den Ende>And this has been the the PhD
work of Iiqing.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3831-0
00:29:26.713 --> 00:29:31.593
<v Martijn Van Den Ende>Who is now a applying these kind
of methods on on DAS data?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3875-0
00:29:34.193 --> 00:29:38.545
<v Martijn Van Den Ende>And so one of the things that
she looked at was, well, how</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3875-1
00:29:38.545 --> 00:29:43.045
<v Martijn Van Den Ende>feasible is it to actually use
an offshore gas cable that is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3875-2
00:29:43.045 --> 00:29:47.841
<v Martijn Van Den Ende>not deployed for the purpose of
back projection and how how much</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3875-3
00:29:47.841 --> 00:29:52.193
<v Martijn Van Den Ende>of A details can we extract from
the back, back projection</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3875-4
00:29:52.193 --> 00:29:53.153
<v Martijn Van Den Ende>procedure so.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3902-0
00:29:53.153 --> 00:29:57.191
<v Martijn Van Den Ende>For this you took one of the the
cables that we have in the in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3902-1
00:29:57.191 --> 00:30:00.909
<v Martijn Van Den Ende>the region and here is an
example for one earthquake here</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3902-2
00:30:00.909 --> 00:30:03.153
<v Martijn Van Den Ende>to the West of this of this
cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3916-0
00:30:03.903 --> 00:30:07.094
<v Martijn Van Den Ende>So you can see this this
beautiful move out of this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3916-1
00:30:07.094 --> 00:30:09.623
<v Martijn Van Den Ende>This, I think it was a magnitude
4 event.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3923-0
00:30:11.473 --> 00:30:13.993
<v Martijn Van Den Ende>So the data were not not
saturated.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3966-0
00:30:15.793 --> 00:30:20.542
<v Martijn Van Den Ende>And in order to make this back
projection work, she had to do a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3966-1
00:30:20.542 --> 00:30:24.847
<v Martijn Van Den Ende>lot of different kinds of
processing. And yeah, basically</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3966-2
00:30:24.847 --> 00:30:29.225
<v Martijn Van Den Ende>apply particular procedure to
convert the raw data that we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3966-3
00:30:29.225 --> 00:30:33.233
<v Martijn Van Den Ende>record to something that is
sufficiently coherent and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3966-4
00:30:33.233 --> 00:30:33.753
<v Martijn Van Den Ende>useful.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3969-0
00:30:35.213 --> 00:30:36.413
<v Martijn Van Den Ende>So some of the steps including.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3996-0
00:30:37.953 --> 00:30:42.170
<v Martijn Van Den Ende>Converting the strain rates to
particle velocity and then</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3996-1
00:30:42.170 --> 00:30:46.750
<v Martijn Van Den Ende>making corrections for the local
settlement layer to make sure</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3996-2
00:30:46.750 --> 00:30:50.895
<v Martijn Van Den Ende>that any uncertainties in the
velocity model are kind of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/3996-3
00:30:50.895 --> 00:30:51.913
<v Martijn Van Den Ende>cancelled out.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4033-0
00:30:54.203 --> 00:30:58.863
<v Martijn Van Den Ende>OK. And so by dividing the
entire cable into these local</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4033-1
00:30:58.863 --> 00:31:03.688
<v Martijn Van Den Ende>sub arrays and then focusing
each of these sub arrays onto</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4033-2
00:31:03.688 --> 00:31:09.085
<v Martijn Van Den Ende>the seismic source, she was able
to very nicely focus or identify</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4033-3
00:31:09.085 --> 00:31:12.683
<v Martijn Van Den Ende>the the origin location of this
earthquake.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4046-0
00:31:13.203 --> 00:31:16.724
<v Martijn Van Den Ende>So here again we have the cable.
Each of these triangles</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4046-1
00:31:16.724 --> 00:31:18.083
<v Martijn Van Den Ende>indicates 1 sub array.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4064-0
00:31:19.233 --> 00:31:22.721
<v Martijn Van Den Ende>And by by focusing each of them
in the right direction, they</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4064-1
00:31:22.721 --> 00:31:25.353
<v Martijn Van Den Ende>kind of intersect here in the
middle, so the.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4073-0
00:31:25.943 --> 00:31:29.470
<v Martijn Van Den Ende>Brighter colors indicate the
strength of the intersection, if</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4073-1
00:31:29.470 --> 00:31:29.983
<v Martijn Van Den Ende>you will.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4095-0
00:31:31.553 --> 00:31:36.242
<v Martijn Van Den Ende>And given that this is just a
small local earthquake, there is</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4095-1
00:31:36.242 --> 00:31:40.113
<v Martijn Van Den Ende>no propagation effect that are
to be recorded here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4128-0
00:31:41.833 --> 00:31:45.957
<v Martijn Van Den Ende>But now what we can do is we can
take a whole bunch of these</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4128-1
00:31:45.957 --> 00:31:50.284
<v Martijn Van Den Ende>small earthquakes and treat them
as empirical Green's functions</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4128-2
00:31:50.284 --> 00:31:54.747
<v Martijn Van Den Ende>to construct a much larger or to
simulate a much larger magnitude</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4128-3
00:31:54.747 --> 00:31:55.153
<v Martijn Van Den Ende>event.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4153-0
00:31:56.243 --> 00:32:00.713
<v Martijn Van Den Ende>So focusing here on this, this
top panel here on the right, our</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4153-1
00:32:00.713 --> 00:32:04.973
<v Martijn Van Den Ende>cable is now over here where we
have these triangles. And So</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4153-2
00:32:04.973 --> 00:32:05.323
<v Martijn Van Den Ende>what?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4169-0
00:32:05.523 --> 00:32:10.046
<v Martijn Van Den Ende>I chain did was taking small
earthquakes that are occurring</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4169-1
00:32:10.046 --> 00:32:13.363
<v Martijn Van Den Ende>in this region and then
basically creating.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4195-0
00:32:15.153 --> 00:32:19.388
<v Martijn Van Den Ende>A line of these, this green
function and sort of stacking</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4195-1
00:32:19.388 --> 00:32:23.988
<v Martijn Van Den Ende>them into a wave form that is
recorded by the by the cable and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4195-2
00:32:23.988 --> 00:32:27.713
<v Martijn Van Den Ende>then by back projecting those
synthetic waveforms.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4215-0
00:32:28.353 --> 00:32:32.690
<v Martijn Van Den Ende>We were able to very accurately
locate the the position and</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4215-1
00:32:32.690 --> 00:32:36.233
<v Martijn Van Den Ende>timing at which each of these
sources is active.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4245-0
00:32:36.833 --> 00:32:40.918
<v Martijn Van Den Ende>So the stars here indicate the
progression of the simulated</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4245-1
00:32:40.918 --> 00:32:45.139
<v Martijn Van Den Ende>magnitude 7 earthquake and the
circles here indicate what you</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4245-2
00:32:45.139 --> 00:32:48.884
<v Martijn Van Den Ende>would get from back, projecting
the wave forms of this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4245-3
00:32:48.884 --> 00:32:49.633
<v Martijn Van Den Ende>earthquake.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4266-0
00:32:51.193 --> 00:32:55.289
<v Martijn Van Den Ende>And what is very nice about this
procedure is that a lot of the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4266-1
00:32:55.289 --> 00:32:59.129
<v Martijn Van Den Ende>work needs to be done can be
done in advance. And so once a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4266-2
00:32:59.129 --> 00:33:01.433
<v Martijn Van Den Ende>proper pipeline is set up, you
can.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4273-0
00:33:02.273 --> 00:33:05.033
<v Martijn Van Den Ende>Operate this pipeline in almost
in real time.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4312-0
00:33:06.673 --> 00:33:11.585
<v Martijn Van Den Ende>So with the DAS data coming in
and with selective windowing</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4312-1
00:33:11.585 --> 00:33:16.334
<v Martijn Van Den Ende>would be able to track the
rupture almost in in real time</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4312-2
00:33:16.334 --> 00:33:21.492
<v Martijn Van Den Ende>and especially for tsunami early
warning, this would be a very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4312-3
00:33:21.492 --> 00:33:24.113
<v Martijn Van Den Ende>useful and valuable tool to use.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4332-0
00:33:27.983 --> 00:33:32.808
<v Martijn Van Den Ende>And so with that, I just want to
give you a little outlook on</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4332-1
00:33:32.808 --> 00:33:35.143
<v Martijn Van Den Ende>where we want to go from here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4353-0
00:33:35.903 --> 00:33:40.499
<v Martijn Van Den Ende>So clearly there is a need for a
larger range in order to do</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4353-1
00:33:40.499 --> 00:33:44.343
<v Martijn Van Den Ende>conventional earthquake related
warning with this.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4365-0
00:33:45.063 --> 00:33:49.069
<v Martijn Van Den Ende>Either that or we need other
clever methods to work around</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4365-1
00:33:49.069 --> 00:33:50.903
<v Martijn Van Den Ende>this limited dynamic range.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4369-0
00:33:51.543 --> 00:33:53.943
<v Martijn Van Den Ende>For instance, we could think of
ways to.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4376-0
00:33:54.713 --> 00:33:56.313
<v Martijn Van Den Ende>Unwrap the data and try to
reconstruct.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4394-0
00:33:57.453 --> 00:34:02.089
<v Martijn Van Den Ende>The original waveform that's
that's turned into a more</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4394-1
00:34:02.089 --> 00:34:05.293
<v Martijn Van Den Ende>saturated waveform when we
record it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4429-0
00:34:05.853 --> 00:34:09.859
<v Martijn Van Den Ende>And so we have actually several
projects in the pipeline where</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4429-1
00:34:09.859 --> 00:34:13.165
<v Martijn Van Den Ende>we're trying to use deep
learning methods to try to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4429-2
00:34:13.165 --> 00:34:16.408
<v Martijn Van Den Ende>recover the original waveform
and then do use more</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4429-3
00:34:16.408 --> 00:34:20.097
<v Martijn Van Den Ende>conventional early warning
methods on these reconstructed</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4429-4
00:34:20.097 --> 00:34:20.733
<v Martijn Van Den Ende>waveforms.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4440-0
00:34:22.193 --> 00:34:25.926
<v Martijn Van Den Ende>And the 2nd Ave. that we're
gonna develop further is trying</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4440-1
00:34:25.926 --> 00:34:26.113
<v Martijn Van Den Ende>to.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4450-0
00:34:26.663 --> 00:34:30.885
<v Martijn Van Den Ende>And develop this this real time
local back projection pipeline</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4450-1
00:34:30.885 --> 00:34:31.623
<v Martijn Van Den Ende>and seeing.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4467-0
00:34:33.193 --> 00:34:36.866
<v Martijn Van Den Ende>How it will work in practice
when we have large earthquakes</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4467-1
00:34:36.866 --> 00:34:39.193
<v Martijn Van Den Ende>that are propagating along the
cable?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4478-0
00:34:40.993 --> 00:34:43.393
<v Martijn Van Den Ende>And with that, I'd like to thank
you for your attention.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4483-0
00:34:52.003 --> 00:34:52.723
<v Guns, Katherine A>Thank you so much.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4491-0
00:34:52.723 --> 00:34:56.826
<v Guns, Katherine A>That was a great talk. We'll
start with any questions in the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4491-1
00:34:56.826 --> 00:34:57.163
<v Guns, Katherine A>room.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4493-0
00:34:57.163 --> 00:34:58.563
<v Guns, Katherine A>We're gonna wrap it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4499-0
00:35:00.173 --> 00:35:01.333
<v Guns, Katherine A>Anne Marie has a question.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4503-0
00:35:01.333 --> 00:35:03.133
<v Guns, Katherine A>And remember, the mic is behind
you, right?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4508-0
00:35:04.673 --> 00:35:05.433
<v Guns, Katherine A>This is Ann revolte.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4509-0
00:35:05.433 --> 00:35:06.033
<v Guns, Katherine A>Thanks so much.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4516-0
00:35:06.033 --> 00:35:07.353
<v Guns, Katherine A>That was a really clear talk.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4518-0
00:35:07.633 --> 00:35:08.433
<v Guns, Katherine A>I'm just curious.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4522-0
00:35:10.233 --> 00:35:10.833
<v Guns, Katherine A>Your conclusion?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4564-0
00:35:10.833 --> 00:35:14.470
<v Guns, Katherine A>How how much of your conclusions
about the dynamic range are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4564-1
00:35:14.470 --> 00:35:17.930
<v Guns, Katherine A>dependent on this particular
setup? And I don't know much</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4564-2
00:35:17.930 --> 00:35:21.508
<v Guns, Katherine A>about DOS at all, but there's
certainly parameters that you</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4564-3
00:35:21.508 --> 00:35:24.907
<v Guns, Katherine A>put in that are specific to
something about the cable, I</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4564-4
00:35:24.907 --> 00:35:27.353
<v Guns, Katherine A>guess and or the the attenuation
in the.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4568-0
00:35:27.513 --> 00:35:28.753
<v Guns, Katherine A>Region offshore Chile.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4583-0
00:35:30.273 --> 00:35:34.342
<v Martijn Van Den Ende>Yeah. Well, let me just go back
to the very first criterion that</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4583-1
00:35:34.342 --> 00:35:36.033
<v Martijn Van Den Ende>I had on on the slide here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4591-0
00:35:37.593 --> 00:35:40.713
<v Martijn Van Den Ende>So this this criterion that you
have over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4615-0
00:35:42.393 --> 00:35:45.550
<v Martijn Van Den Ende>Kind of is is sort of shared by
the majority of DAS</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4615-1
00:35:45.550 --> 00:35:49.316
<v Martijn Van Den Ende>interrogators, at least as far
as I can tell, because I'm not</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4615-2
00:35:49.316 --> 00:35:50.713
<v Martijn Van Den Ende>really a photonics guy.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4634-0
00:35:50.713 --> 00:35:53.593
<v Martijn Van Den Ende>So I don't know the exact
details of how these</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4634-1
00:35:53.593 --> 00:35:57.392
<v Martijn Van Den Ende>interrogators work, but from
what I've gathered by discussing</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4634-2
00:35:57.392 --> 00:35:59.353
<v Martijn Van Den Ende>with with various manufacturers.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4649-0
00:36:00.763 --> 00:36:03.757
<v Martijn Van Den Ende>This is would be the
relationship that would apply to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4649-1
00:36:03.757 --> 00:36:05.643
<v Martijn Van Den Ende>a lot of interrogators out
there.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4672-0
00:36:07.233 --> 00:36:10.426
<v Martijn Van Den Ende>Because this is simply the sort
of measurement principle of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4672-1
00:36:10.426 --> 00:36:13.833
<v Martijn Van Den Ende>tasks, and that is really just a
matter of how you estimate the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4672-2
00:36:13.833 --> 00:36:14.153
<v Martijn Van Den Ende>phase.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4686-0
00:36:15.093 --> 00:36:18.758
<v Martijn Van Den Ende>But using most standard ways of
estimating phase, this is what</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4686-1
00:36:18.758 --> 00:36:19.573
<v Martijn Van Den Ende>you would get.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4711-0
00:36:19.573 --> 00:36:23.881
<v Martijn Van Den Ende>And So what goes in there is the
wavelength of light, which is,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4711-1
00:36:23.881 --> 00:36:27.853
<v Martijn Van Den Ende>well, kind of fixed by the the
core diameter of the fiber.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4719-0
00:36:28.293 --> 00:36:30.978
<v Martijn Van Den Ende>And then you have the refractive
index and the photodetect</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4719-1
00:36:30.978 --> 00:36:32.253
<v Martijn Van Den Ende>coefficient that are simply.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4736-0
00:36:33.793 --> 00:36:37.668
<v Martijn Van Den Ende>Material properties of the fibre
and then these two guys here are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4736-1
00:36:37.668 --> 00:36:39.313
<v Martijn Van Den Ende>your acquisition parameters.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4749-0
00:36:39.953 --> 00:36:43.698
<v Martijn Van Den Ende>So if you could go to a very
high time, something like very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4749-1
00:36:43.698 --> 00:36:46.633
<v Martijn Van Den Ende>high spatial something rate, you
could really.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4781-0
00:36:47.333 --> 00:36:52.129
<v Martijn Van Den Ende>Bump up this dynamic range by a
lot, but unfortunately this time</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4781-1
00:36:52.129 --> 00:36:56.556
<v Martijn Van Den Ende>sampling rate is kind of has
like an upper bound by the the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4781-2
00:36:56.556 --> 00:37:01.131
<v Martijn Van Den Ende>range of your cable like. The
longer you are sensing in terms</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4781-3
00:37:01.131 --> 00:37:05.633
<v Martijn Van Den Ende>of range, the longer you have to
wait for the light to come.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4798-0
00:37:05.633 --> 00:37:09.548
<v Martijn Van Den Ende>Back and so there is an upper
limit to how well I would say a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4798-1
00:37:09.548 --> 00:37:12.453
<v Martijn Van Den Ende>lower limit of how small this
delta T can be.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4812-0
00:37:13.233 --> 00:37:17.538
<v Martijn Van Den Ende>And likewise there is a limit on
how small your gauge length or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4812-1
00:37:17.538 --> 00:37:19.153
<v Martijn Van Den Ende>spatial sampling can be.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4825-0
00:37:19.933 --> 00:37:24.813
<v Martijn Van Den Ende>And so really there is a bounds
to how how large the strain</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4825-1
00:37:24.813 --> 00:37:27.173
<v Martijn Van Den Ende>rates you can you can record.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4836-0
00:37:31.193 --> 00:37:34.830
<v Guns, Katherine A>Awesome. Thanks. We're having a
little bit of static, I think</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4836-1
00:37:34.830 --> 00:37:36.473
<v Guns, Katherine A>from potentially your audio.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4842-0
00:37:37.803 --> 00:37:38.723
<v Martijn Van Den Ende>Ah, OK.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4855-0
00:37:38.033 --> 00:37:40.950
<v Guns, Katherine A>I'm not sure if there's anything
you can check your plug in or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4855-1
00:37:40.950 --> 00:37:42.433
<v Guns, Katherine A>connection, but we can hear you.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4857-0
00:37:42.303 --> 00:37:42.423
<v Martijn Van Den Ende>Umm.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4861-0
00:37:42.433 --> 00:37:44.033
<v Guns, Katherine A>But there's just a little bit of
background static.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4870-0
00:37:45.463 --> 00:37:47.743
<v Martijn Van Den Ende>OK, it might be Internet
connection.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4877-0
00:37:48.623 --> 00:37:51.103
<v Martijn Van Den Ende>I'm not hearing anything myself
over here so.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4879-0
00:37:51.133 --> 00:37:51.573
<v Guns, Katherine A>OK, OK.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4891-0
00:37:52.093 --> 00:37:54.693
<v Guns, Katherine A>Well, we'll keep going forward,
but if it gets worse, I'll, I'll</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4891-1
00:37:54.693 --> 00:37:55.213
<v Guns, Katherine A>let you know.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4890-0
00:37:55.643 --> 00:37:55.923
<v Martijn Van Den Ende>OK.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4895-0
00:37:56.833 --> 00:37:58.553
<v Guns, Katherine A>So questions in the room.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4903-0
00:38:01.463 --> 00:38:04.223
<v Guns, Katherine A>If not, then we'll go to Ben
Brooks again, question.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4907-0
00:38:05.503 --> 00:38:06.383
<v Brooks, Benjamin A>Can you hear me OK?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4908-0
00:38:06.883 --> 00:38:07.363
<v Martijn Van Den Ende>Yes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4920-0
00:38:08.233 --> 00:38:12.953
<v Brooks, Benjamin A>Yeah, maybe the static is the
the desk saturation possible.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4926-0
00:38:15.633 --> 00:38:16.593
<v Brooks, Benjamin A>Thanks for thanks.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4941-0
00:38:16.633 --> 00:38:19.975
<v Brooks, Benjamin A>Really interesting. And as Emory
said, really clearly presented</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4941-1
00:38:19.975 --> 00:38:22.273
<v Brooks, Benjamin A>talk and sorry if this is a
silly question.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4963-0
00:38:22.433 --> 00:38:26.208
<v Brooks, Benjamin A>The slide that you showed where
you were detecting the open</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4963-1
00:38:26.208 --> 00:38:30.046
<v Brooks, Benjamin A>ocean swells moved a little fast
for me to see what what the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4963-2
00:38:30.046 --> 00:38:33.443
<v Brooks, Benjamin A>periods were, but is there any
possibility of tsunami</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4963-3
00:38:33.443 --> 00:38:34.073
<v Brooks, Benjamin A>detection?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4981-0
00:38:35.743 --> 00:38:39.166
<v Martijn Van Den Ende>Yeah, that's very interesting
question. And I think there are</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4981-1
00:38:39.166 --> 00:38:41.983
<v Martijn Van Den Ende>several groups in the world
working on that topic.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4999-0
00:38:42.783 --> 00:38:47.698
<v Martijn Van Den Ende>We actually have a PhD student
at Yale who looked at these sort</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/4999-1
00:38:47.698 --> 00:38:50.463
<v Martijn Van Den Ende>of theoretical feasibility of
that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5034-0
00:38:52.033 --> 00:38:56.238
<v Martijn Van Den Ende>And then kind of towards the end
of his PhD, other people</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5034-1
00:38:56.238 --> 00:39:00.588
<v Martijn Van Den Ende>actually published the first
sort of sightings of a tsunami</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5034-2
00:39:00.588 --> 00:39:04.793
<v Martijn Van Den Ende>with DAZ, although it's, it was
very faint in my opinion.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5047-0
00:39:05.803 --> 00:39:09.762
<v Martijn Van Den Ende>But certainly if you, especially
if you have a shallow cable or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5047-1
00:39:09.762 --> 00:39:11.123
<v Martijn Van Den Ende>like in shallow water.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5061-0
00:39:12.673 --> 00:39:16.393
<v Martijn Van Den Ende>It is quite likely that that you
can record a tsunami.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5096-0
00:39:17.713 --> 00:39:21.678
<v Martijn Van Den Ende>I've also been asked whether
that can actually saturate the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5096-1
00:39:21.678 --> 00:39:25.180
<v Martijn Van Den Ende>desk recordings which maybe
would have been a second</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5096-2
00:39:25.180 --> 00:39:29.079
<v Martijn Van Den Ende>question you wanted to ask, but
that is not very likely to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5096-3
00:39:29.079 --> 00:39:32.846
<v Martijn Van Den Ende>happen. So tsunami seem to be
sitting in a sort of happy</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5096-4
00:39:32.846 --> 00:39:35.953
<v Martijn Van Den Ende>medium between being detectable
and still not.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5101-0
00:39:36.073 --> 00:39:37.233
<v Martijn Van Den Ende>Saturating the data.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5106-0
00:39:39.523 --> 00:39:40.203
<v Brooks, Benjamin A>Yeah, I wonder.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5116-0
00:39:41.003 --> 00:39:43.590
<v Brooks, Benjamin A>I mean, maybe you could design
some kind of match filter,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5116-1
00:39:43.590 --> 00:39:44.483
<v Brooks, Benjamin A>something like that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5123-0
00:39:44.483 --> 00:39:47.723
<v Brooks, Benjamin A>That might help you with the the
seismic aspect of it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5133-0
00:39:51.193 --> 00:39:53.153
<v Martijn Van Den Ende>I mean in terms of detection or?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5162-0
00:39:53.483 --> 00:39:58.283
<v Brooks, Benjamin A>Yeah. Yeah. I mean, if you could
potentially use use coincident</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5138-0
00:39:54.793 --> 00:39:54.953
<v Martijn Van Den Ende>Kind of.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5162-1
00:39:58.283 --> 00:40:02.783
<v Brooks, Benjamin A>tsunami data or model to feed
back into your detection, but</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5162-2
00:40:02.783 --> 00:40:06.683
<v Brooks, Benjamin A>that might not be useful in the
time period of eew.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5167-0
00:40:08.193 --> 00:40:08.633
<v Brooks, Benjamin A>But maybe.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5187-0
00:40:08.203 --> 00:40:12.123
<v Martijn Van Den Ende>Yeah, normally you don't want to
wait for tsunami to pass by to</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5187-1
00:40:12.123 --> 00:40:14.083
<v Martijn Van Den Ende>send out an an earthquake alert.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5182-0
00:40:12.203 --> 00:40:12.403
<v Brooks, Benjamin A>Right.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5201-0
00:40:14.083 --> 00:40:18.331
<v Martijn Van Den Ende>So I mean it does have to
propagate to be detectable over</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5192-0
00:40:15.593 --> 00:40:16.033
<v Brooks, Benjamin A>Exactly.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5201-1
00:40:18.331 --> 00:40:20.163
<v Martijn Van Den Ende>by the, by the cable, so.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5229-0
00:40:20.663 --> 00:40:25.125
<v Brooks, Benjamin A>Just maybe more in terms of just
source, you know and and so so</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5215-0
00:40:25.023 --> 00:40:25.903
<v Martijn Van Den Ende>Yes. Yeah.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5229-1
00:40:25.125 --> 00:40:29.587
<v Brooks, Benjamin A>near near real time situational
awareness instead of instead of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5229-2
00:40:29.587 --> 00:40:30.703
<v Brooks, Benjamin A>EW specifically.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5231-0
00:40:31.483 --> 00:40:32.083
<v Martijn Van Den Ende>Yeah, yeah.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5233-0
00:40:33.793 --> 00:40:34.073
<v Brooks, Benjamin A>Yes.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5235-0
00:40:34.803 --> 00:40:35.363
<v Martijn Van Den Ende>No, thank you.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5238-0
00:40:37.103 --> 00:40:38.583
<v Guns, Katherine A>I think Theresa, good question.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5244-0
00:40:41.283 --> 00:40:42.443
<v Sawi, Theresa M>Yes, hi. My name.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5251-0
00:40:42.443 --> 00:40:44.163
<v Sawi, Theresa M>Thank you so much for your talk.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5259-0
00:40:44.163 --> 00:40:48.483
<v Sawi, Theresa M>I'm actually calling in from the
DAS SSA Photonics conference.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5268-0
00:40:50.033 --> 00:40:52.033
<v Sawi, Theresa M>And so this is very appropriate
on brand.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5273-0
00:40:52.713 --> 00:40:53.873
<v Sawi, Theresa M>I have a few questions.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5291-0
00:40:53.873 --> 00:40:59.434
<v Sawi, Theresa M>One, I think I saw in your map
that the cable may be actually</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5291-1
00:40:59.434 --> 00:41:02.753
<v Sawi, Theresa M>crossing a fault line. Is that
true?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5309-0
00:41:03.353 --> 00:41:08.327
<v Sawi, Theresa M>And if so, or maybe even in any
case, are you worried in the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5309-1
00:41:08.327 --> 00:41:11.753
<v Sawi, Theresa M>event of a large earthquake of
the cable?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5311-0
00:41:12.853 --> 00:41:13.813
<v Sawi, Theresa M>Breaking.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5333-0
00:41:16.143 --> 00:41:20.197
<v Martijn Van Den Ende>Well, it's quite likely that
there are several smaller faults</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5333-1
00:41:20.197 --> 00:41:23.663
<v Martijn Van Den Ende>on the sea floor that are either
mapped or unmapped.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5354-0
00:41:25.233 --> 00:41:29.712
<v Martijn Van Den Ende>But these are commercial telecom
cables, so these have been sort</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5354-1
00:41:29.712 --> 00:41:32.193
<v Martijn Van Den Ende>of tried and tested over the
years.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5357-0
00:41:32.753 --> 00:41:34.753
<v Martijn Van Den Ende>So at least over the last few
years.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5382-0
00:41:36.393 --> 00:41:39.849
<v Martijn Van Den Ende>Where there were significant
earthquakes but none of them</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5382-1
00:41:39.849 --> 00:41:43.485
<v Martijn Van Den Ende>managed to actually break the
cable, you would have to be, I</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5382-2
00:41:43.485 --> 00:41:45.393
<v Martijn Van Den Ende>think, pretty unlucky to really.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5394-0
00:41:46.133 --> 00:41:49.173
<v Martijn Van Den Ende>Snap a cable, but I've heard
reports of it happening.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5412-0
00:41:49.173 --> 00:41:52.995
<v Martijn Van Den Ende>Then there's always a question
whether it is the ground sort of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5412-1
00:41:52.995 --> 00:41:56.699
<v Martijn Van Den Ende>displacement itself, or like a
subsequent submarine landslide</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5412-2
00:41:56.699 --> 00:41:58.133
<v Martijn Van Den Ende>that that broke it, but.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5436-0
00:41:59.753 --> 00:42:03.478
<v Martijn Van Den Ende>Yeah. So that might be a
possibility. Perhaps in the case</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5436-1
00:42:03.478 --> 00:42:07.524
<v Martijn Van Den Ende>of a large earthquakes that any
submarine landslides will kind</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5436-2
00:42:07.524 --> 00:42:08.873
<v Martijn Van Den Ende>of destroy the cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5458-0
00:42:10.553 --> 00:42:13.845
<v Martijn Van Den Ende>But hopefully at that point we
would have already sort of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5458-1
00:42:13.845 --> 00:42:17.478
<v Martijn Van Den Ende>acquired the data and the data
should be safe and sound at this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5458-2
00:42:17.478 --> 00:42:18.273
<v Martijn Van Den Ende>landing point.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5461-0
00:42:19.383 --> 00:42:20.023
<v Martijn Van Den Ende>On land.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5466-0
00:42:20.743 --> 00:42:22.223
<v Martijn Van Den Ende>So we could still do something
with it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5470-0
00:42:24.363 --> 00:42:26.163
<v Sawi, Theresa M>And then another question is.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5474-0
00:42:28.273 --> 00:42:30.473
<v Sawi, Theresa M>For locations.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5486-0
00:42:32.073 --> 00:42:35.793
<v Sawi, Theresa M>How certain are you of the
locations of the cables?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5490-0
00:42:35.793 --> 00:42:38.033
<v Sawi, Theresa M>Do they drift about?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5499-0
00:42:38.193 --> 00:42:42.233
<v Sawi, Theresa M>I mean, I I'm sure they're
buried to some degree, but then.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5505-0
00:42:43.953 --> 00:42:45.033
<v Sawi, Theresa M>Do they migrate at all?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5519-0
00:42:45.393 --> 00:42:50.373
<v Sawi, Theresa M>Are like do the telecom
companies even know themselves</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5519-1
00:42:50.373 --> 00:42:53.633
<v Sawi, Theresa M>the exact location of these
cables?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5524-0
00:42:55.283 --> 00:42:57.483
<v Sawi, Theresa M>How certain are you of their
locations?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5548-0
00:42:59.053 --> 00:43:02.121
<v Martijn Van Den Ende>Yeah. So the telecom companies
are not necessarily certain</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5548-1
00:43:02.121 --> 00:43:05.501
<v Martijn Van Den Ende>about the location of the cable,
but they were certain about the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5548-2
00:43:05.501 --> 00:43:07.893
<v Martijn Van Den Ende>location of the boat that
deployed the cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5560-0
00:43:08.333 --> 00:43:12.146
<v Martijn Van Den Ende>So what we were given was
basically the trajectory of the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5560-1
00:43:12.146 --> 00:43:14.053
<v Martijn Van Den Ende>boat that deployed the cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5575-0
00:43:15.593 --> 00:43:19.070
<v Martijn Van Den Ende>With with various parameters
like whether the cable was</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5575-1
00:43:19.070 --> 00:43:20.313
<v Martijn Van Den Ende>trenched or not and.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5579-0
00:43:21.953 --> 00:43:22.913
<v Martijn Van Den Ende>Yeah. So in these cases.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5589-0
00:43:24.633 --> 00:43:28.433
<v Martijn Van Den Ende>We have sort of a reasonable
grip on where the cable is.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5612-0
00:43:29.753 --> 00:43:33.347
<v Martijn Van Den Ende>On the orientation, because
depending on the amount of slack</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5612-1
00:43:33.347 --> 00:43:36.353
<v Martijn Van Den Ende>on the cable it could kind of
wiggle a little bit.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5657-0
00:43:36.353 --> 00:43:40.630
<v Martijn Van Den Ende>And so it could be oriented a
bit more East or West. And we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5657-1
00:43:40.630 --> 00:43:45.193
<v Martijn Van Den Ende>have seen not for these cables,
but for other cables in shallow</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5657-2
00:43:45.193 --> 00:43:49.470
<v Martijn Van Den Ende>water we have seen some ROV
footage showing that the cables</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5657-3
00:43:49.470 --> 00:43:54.033
<v Martijn Van Den Ende>is well, you know it makes loops
it, it sort of wiggles around.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5659-0
00:43:54.153 --> 00:43:54.753
<v Martijn Van Den Ende>It's even.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5670-0
00:43:55.553 --> 00:43:59.722
<v Martijn Van Den Ende>Managed to get sort of suspend
in the air by a chair on the sea</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5670-1
00:43:59.722 --> 00:44:00.113
<v Martijn Van Den Ende>floor.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5698-0
00:44:01.403 --> 00:44:04.783
<v Martijn Van Den Ende>So all sorts of weird things
happen on the sea floor with the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5698-1
00:44:04.783 --> 00:44:07.891
<v Martijn Van Den Ende>cable, but at least the location
is sort of more or less</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5698-2
00:44:07.891 --> 00:44:11.163
<v Martijn Van Den Ende>constrained by the trajectory of
the ship that deployed it.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5711-0
00:44:12.713 --> 00:44:15.953
<v Martijn Van Den Ende>But yeah, it will not be super
precise.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5731-0
00:44:15.953 --> 00:44:19.222
<v Martijn Van Den Ende>So depending on what you want to
do, you might have to do a</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5731-1
00:44:19.222 --> 00:44:22.328
<v Martijn Van Den Ende>survey to actually locate the
cable, which could be very</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5731-2
00:44:22.328 --> 00:44:22.873
<v Martijn Van Den Ende>expensive.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5749-0
00:44:25.783 --> 00:44:31.257
<v Sawi, Theresa M>And then one last question,
looking at the equation you were</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5749-1
00:44:31.257 --> 00:44:36.103
<v Sawi, Theresa M>giving in terms of magnitude and
the the propagation.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5751-0
00:44:37.673 --> 00:44:38.233
<v Sawi, Theresa M>Term.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5756-0
00:44:43.263 --> 00:44:45.343
<v Sawi, Theresa M>Yeah. The that middle term
there.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5762-0
00:44:46.913 --> 00:44:48.593
<v Sawi, Theresa M>Does that have? Like any?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5779-0
00:44:48.593 --> 00:44:52.782
<v Sawi, Theresa M>Yeah, the propagation medium
does that take into account the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5779-1
00:44:52.782 --> 00:44:55.873
<v Sawi, Theresa M>conduit conditions or the burial
conditions.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5788-0
00:44:55.873 --> 00:45:00.553
<v Sawi, Theresa M>Because I know that can really
affect the amplitude.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5795-0
00:45:02.393 --> 00:45:05.273
<v Sawi, Theresa M>Of recording of the DAS cable.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5802-0
00:45:07.433 --> 00:45:08.113
<v Sawi, Theresa M>So does that.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5807-0
00:45:08.113 --> 00:45:12.393
<v Sawi, Theresa M>Is that taken into account in
this equation anywhere?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5814-0
00:45:13.593 --> 00:45:15.673
<v Martijn Van Den Ende>Yeah, that's that's a that's a
really good point.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5831-0
00:45:15.673 --> 00:45:21.518
<v Martijn Van Den Ende>And you can actually see it in
the wave forms a little bit. If</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5831-1
00:45:21.518 --> 00:45:24.673
<v Martijn Van Den Ende>I go back to the waterfall
plots.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5868-0
00:45:24.993 --> 00:45:28.936
<v Martijn Van Den Ende>Yeah. So you can see here that
there seems to be some sort of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5868-1
00:45:28.936 --> 00:45:32.815
<v Martijn Van Den Ende>gaps in the recordings these
sort of vertical whitish lines,</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5868-2
00:45:32.815 --> 00:45:36.822
<v Martijn Van Den Ende>those are sections of the cable
that are not very well coupled</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5868-3
00:45:36.822 --> 00:45:37.713
<v Martijn Van Den Ende>to the ground.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5875-0
00:45:37.913 --> 00:45:40.873
<v Martijn Van Den Ende>And so they record amplitudes at
much lower values.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5879-0
00:45:41.673 --> 00:45:42.873
<v Martijn Van Den Ende>Than well coupled sections.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5883-0
00:45:43.663 --> 00:45:44.863
<v Martijn Van Den Ende>And this is another.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5887-0
00:45:46.553 --> 00:45:47.433
<v Martijn Van Den Ende>Avenue to to explore.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5913-0
00:45:49.233 --> 00:45:53.486
<v Martijn Van Den Ende>Because if these if the coupling
coefficient is basically just</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5913-1
00:45:53.486 --> 00:45:57.605
<v Martijn Van Den Ende>sort of a scalar multiplier that
it doesn't affect frequency</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5913-2
00:45:57.605 --> 00:45:58.753
<v Martijn Van Den Ende>content too much.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5932-0
00:46:00.473 --> 00:46:04.539
<v Martijn Van Den Ende>And if it is sort of just linear
and constant in time, then we</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5932-1
00:46:04.539 --> 00:46:06.153
<v Martijn Van Den Ende>can actually use this as.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5950-0
00:46:07.753 --> 00:46:11.316
<v Martijn Van Den Ende>Sections that have sort of an
apparently higher dynamic range</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5950-1
00:46:11.316 --> 00:46:14.938
<v Martijn Van Den Ende>because they simply did records
the the wave fields with lower</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5950-2
00:46:14.938 --> 00:46:15.513
<v Martijn Van Den Ende>amplitude.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/5953-0
00:46:17.403 --> 00:46:17.883
<v Martijn Van Den Ende>From what?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6003-0
00:46:17.963 --> 00:46:22.371
<v Martijn Van Den Ende>From some initial exploration,
we found that the variation in</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6003-1
00:46:22.371 --> 00:46:26.425
<v Martijn Van Den Ende>this coupling factors of the
order of a factor 10, which</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6003-2
00:46:26.425 --> 00:46:30.763
<v Martijn Van Den Ende>sounds like a lot, but because
of the logarithmic scaling of</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6003-3
00:46:30.763 --> 00:46:35.100
<v Martijn Van Den Ende>magnitudes, it doesn't help that
much. In the end, you would</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6003-4
00:46:35.100 --> 00:46:37.803
<v Martijn Van Den Ende>really need sections that have a
cou.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6017-0
00:46:38.043 --> 00:46:43.105
<v Martijn Van Den Ende>Of this, less than essentially
maybe like a factor of 1000 or</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6017-1
00:46:43.105 --> 00:46:45.963
<v Martijn Van Den Ende>so, in order to faithfully
record.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6020-0
00:46:46.723 --> 00:46:47.043
<v Martijn Van Den Ende>The wave forms.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6031-0
00:46:47.533 --> 00:46:50.613
<v Martijn Van Den Ende>But we actually do have a few of
those channels on land.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6059-0
00:46:50.613 --> 00:46:55.460
<v Martijn Van Den Ende>So if you look here close to the
edge of each of the panels, this</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6059-1
00:46:55.460 --> 00:47:00.160
<v Martijn Van Den Ende>is a section that is on land and
those sections were not at all</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6059-2
00:47:00.160 --> 00:47:04.053
<v Martijn Van Den Ende>saturated. And that gave us this
waveform over here.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6089-0
00:47:05.603 --> 00:47:09.192
<v Martijn Van Den Ende>So it is possible, but you have
to be lucky that certain</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6089-1
00:47:09.192 --> 00:47:13.348
<v Martijn Van Den Ende>sections are sufficiently poorly
coupled to be able to record the</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6089-2
00:47:13.348 --> 00:47:15.363
<v Martijn Van Den Ende>waveform without any distortion.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6095-0
00:47:15.363 --> 00:47:18.963
<v Martijn Van Den Ende>And then there's the question,
do you really record the wave?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6107-0
00:47:19.533 --> 00:47:23.773
<v Martijn Van Den Ende>Form properly? Or is there like
other factors involved?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6100-0
00:47:19.933 --> 00:47:21.213
<v Sawi, Theresa M>So OK.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6112-0
00:47:26.623 --> 00:47:27.423
<v Sawi, Theresa M>Thank you so much.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6114-0
00:47:27.423 --> 00:47:28.743
<v Sawi, Theresa M>I've really enjoyed your talk.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6116-0
00:47:29.533 --> 00:47:30.053
<v Martijn Van Den Ende>No, thank you.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6123-0
00:47:32.353 --> 00:47:35.313
<v Guns, Katherine A>OK. Questions. Any more
questions in the room?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6133-0
00:47:36.883 --> 00:47:39.763
<v Guns, Katherine A>Everybody. And I'm not seeing
any more questions online.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6134-0
00:47:39.763 --> 00:47:40.963
<v Guns, Katherine A>Last chance, anybody?</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6142-0
00:47:43.213 --> 00:47:45.835
<v Guns, Katherine A>OK, then let's go ahead and take
Martian one more time for his</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6142-1
00:47:45.835 --> 00:47:46.293
<v Guns, Katherine A>great talk.</v>

e1a6d0f5-c720-4206-b6ae-9c1973856016/6147-0
00:47:50.503 --> 00:47:51.823
<v Martijn Van Den Ende>And you was a pleasure to be
there.</v>