[S-SS03] New trends in data acquisition, analysis and interpretation of seismicity

[SSS03-P01] Quantifying space-time earthquake clustering on a given fault network

*Natalie Bladis¹、Ilya Zaliapin¹ (1.University of Nevada, Reno)

キーワード：clustering, seismicity, earthquakes, localization

Earthquake clustering is a fundamental component of seismicity that reflects various forms of
earthquake triggering mechanisms. Zaliapin and Ben-Zion (SRL, 2021) introduced a simple and
robust measure of space-time clustering, using the receiver operating characteristic (ROC)
diagram, that allows disentangling effects related to concentration of events around a
heterogeneous regional fault network (marginal space distribution of events) from coupled
space-time fluctuations (joint space-time distribution). Their analysis has shown that the overall
observed earthquake clustering is high, with the marginal space clustering playing a dominant
role in the catalog clustering for a variety of regional catalogs and the global seismicity. At the
same time, when one removes the marginal clustering and focuses on the coupled space-time
clustering, different catalogs show different degrees of clustering, reflecting a variety of specific
triggering conditions and mechanisms. Here we discuss what degree of clustering one should
expect in a spatially inhomogeneous non-stationary process, assuming that its time and space
components are independent, and how to assess observed deviations from this null hypothesis.
We apply the discussed approach to examine the raw and background seismicity in various
seismically active regions. We discuss robustness of the results with respect to the lower
magnitude cutoff and spatio-temporal resolutions of analysis, and relative importance of the
marginal space clustering vs. coupled space-time clustering in different environments.
Reference: Zaliapin, I. and Y. Ben-Zion (2021) Perspectives on clustering and declustering of
earthquakes. Seismological Research Letters, 93 (1): 386–401 doi:10.1785/0220210127