Good afternoon. I’m Jonathan Stewart.
I’m glad to be joining you by video today.
I will be talking about the GEER response
for a potential future northern California earthquake.
So I am a co-PI of the Geotechnical Extreme Events Reconnaissance
Association, GEER. I’ll be making this video presentation.
Due to a scheduling conflict, I’m unable to join you live.
Thankfully, the live analyst from GEER who is joining you, to whom
I’m very grateful, is Robb Moss from Cal Poly-San Luis Obispo.
And Robb is a very experienced of GEER
and a member of our steering committee.
What I’d like to do in this presentation is really two things – to tell you just
a few things about GEER, for those of you who may not be familiar with
our organization, and then to talk about some resources that the GEER team
would likely use when they deploy for an event in northern California.
What is GEER? GEER is a volunteer organization
of geotechnical engineers, engineering geologists,
Earth scientists from a broad spectrum of backgrounds.
We respond to geotechnical extreme events, like earthquakes, within the
United States and around the world. And we conduct reconnaissance,
and we document our observations, hopefully in a timely way.
We seek to collect valuable perishable data that can be used
to advance research and improve engineering practice
due to the development of improved models.
As we do our work, we try to form diverse reconnaissance teams that
would have the required expertise given the circumstances of an event
and would have both experienced researchers, established experts,
as well as more junior researchers who are interested
in working with reconnaissance.
GEER is part of a broader reconnaissance community
that is supported by the National Science Foundation.
GEER is part of this CONVERGE organization with
seven different so-called EERs. Of these seven, GEER is the first.
It was founded over 20 years ago and has responded to a large number
of events. GEER basically was the model under which
these other organizations were formed.
Aside from the EERs, there is support from the reconnaissance enterprise
through DesignSafe Cyberinfrastructure at University of Texas.
And, among other things, DesignSafe is the repository
where our data goes after our work is complete.
We also are supported by the Natural Hazards Reconnaissance Facility –
RAPID – at the University of Washington, which provides
equipment and the expertise on how to use it.
GEER has responded to over 70 events during its history,
and the locations are shown here. You can see it’s truly global,
and it’s not just earthquakes. There’s a variety of
extreme events that we’ve responded to.
Part of GEER’s work is education and outreach.
Back in the days before COVID, we would do in-person events,
either for a major event briefing or to provide training.
And this training would usually be talking about strategies for
conducting effective reconnaissance and hands-on equipment training.
Of course, we also do online events, especially for the last few years –
webinars and workshops, again, related to
a particular earthquake or more general training.
We also do joint training with our sister organizations, RAPID,
DesignSafe, and CONVERGE. And we have sponsored
special sessions at major conferences.
Now, the second part of my remarks, I just want to comment on some of
the resources that we would likely use in a team that is responding
to a northern California earthquake.
It would be much the same for a southern California earthquake.
One of the most basic resources we would use anywhere in the world,
actually, is the USGS ShakeMap.
It gives a very rapid sense of where shaking is stronger and weaker.
So here’s one for the Loma Prieta earthquake.
A tool from USGS we’ve been using recently is the near-real-time
liquefaction map using liquefaction geospatial models.
And these models provide liquefaction probabilities, which are marked
over here, with hotter colors indicating higher probabilities.
And you can basically overlay where you actually see liquefaction effects
on these probability maps, and this type of result is, I think, increasingly going
to be featured in future GEER reports, for earthquakes anyhow.
Now, one thing that’s particular to urban California – the Bay Area
and southern California – is California Geological Survey
has maps of zones of required investigation for liquefaction
and landslides. Also surface fault rupture.
So you see here, for example, the green are liquefaction zones.
The sort of darker brown are landslide zones.
And these would be an extremely valuable resource to a team that
is deploying into the field because it’s where you
might expect to see these different hazards.
One of the things that we do very often in recent reconnaissance exercises is
conduct detailed reconnaissance in the area around a ground motion station.
Again, if you think about the fact that we’re trying to use these observations
to support model development in the area near a ground motion station,
you know what the ground motion was.
So it’s a better case history than one where you don’t know it.
And so we have these locations. It’s saved in NGA relational databases.
And these would be ground motion stations that have
recorded past earthquakes. And so this is the type of information
we would certainly send with a team going into the field.
And then the last item I’ll mention, which is a fairly recent one, GEER has
begun working with the NGL project – Next Generation Liquefaction.
And, in this collaboration, we can take the NGL database,
which is a database of case histories of liquefaction, or non-liquefaction.
Each case history has, of course, a location.
It has an observed field performance. And it has geotechnical data,
among other things. And, by re-occupying these sites
where there’s been prior observations, we can really learn something about,
you know, what kinds of events would trigger liquefaction
and what ones would not.
The map here is a static image, but in the – in the real database,
you can zoom in as much as you want and see rather specifically where
different observations were made for the case histories in the database.
So, with that, I’ll conclude my remarks.
I appreciate your attention, and I wish you a productive meeting.
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