Re-Evaluating Seismic Background Rates: Implications for Remote Dynamic Triggering

Kristine Pankow

University of Utah

Date & Time
Building 3, Rambo Auditorium

The phenomenon of remote dynamic triggering has been well-established since the
1992 Landers, California, earthquake triggered earthquakes from California to Yellowstone.
Since then, there have been many other studies that have clearly shown a direct link between
remote mainshocks and small magnitude local seismicity. With the development of matched
filter and other detection algorithms, there is an increasing number of instances documenting
remote triggering. However, in many studies the triggering criteria is based on examining the
number of earthquakes in small time windows surrounding the arrival of the teleseismic waves
and rarely is the null hypothesis, that the rate change is merely a random occurrence, fully tested.
In this study using 33 years (1985-2017) of data, we investigate if 500 mainshocks (489 global,
11 regional) statistically trigger remote aftershocks. We compare these results to results
determined using the beta statistic and evaluating rate changes assuming a Poisson distribution.
While the main goal of this work is to explore the statistics used as criteria for determining
dynamic triggering and what is meant by statistical significance, we also identify previously
undocumented cases of dynamic triggering, such as triggering in Yellowstone following the
1985 M8.0 Mexico City earthquake.

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