SCEC Award Number 19063 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Temporal changes of seismicity in relation to preparation processes of large earthquakes and decade-scale climate changes
Investigator(s)
Name Organization
Ilya Zaliapin University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants A graduate students at UNR, TBN and a graduate student at USC, TBN
SCEC Priorities 2e, 3d, 1d SCEC Groups Seismology, EFP, FARM
Report Due Date 03/15/2020 Date Report Submitted 03/15/2020
Project Abstract
 The goal of the current project is to quantify non-stationary aspects of seismicity, with a focus on dynamics of seismicity and preparation processes of large earthquakes. Specifically, we developed a time-dependent versions of previously designed spatial techniques, and apply them to the observed seismicity of southern California. The project goals include the following tasks: Examine changes in earthquake patterns during preparation processes of large earthquakes in California. The analysis will include the Landers (1992, M7.3), Northridge (1994, M6.7), Hector Mine (1999, M7.1), and El Mayor Cucapah (2010, M7.2) earthquakes in southern California. We also examined the Parkfield (2004, M6.0) earthquake in northern California, as a case of a relatively isolated natural system (rupture surrounded by creeping zones). We also examined progressive coalescence of individual earthquakes into clusters. Continuing studies with these techniques, combined with analysis of geodetic data and insights from laboratory experiments and model simulations, can improve the ability to track preparation processes leading to large earthquakes.
Intellectual Merit The project developed a methodology for robust quantification of the occurrence and localization of earthquake-induced rock damage prior to large earthquakes. The methodology has been tested in Southern California, the Parkfield section of San Andreas Fault, and Turkey. The project provided further classification of earthquake clustering and earthquake repeaters in relation to earthquake preparation process, using the data in the Sea of Marmara. Finally, we started exploration of the hyperbolic geometry of the earthquake field, as a way of providing a background for the nearest-neighbor earthquake methodology developed and used in this project.
Broader Impacts The project obtains a suit of results that have an impact on research areas outside of the immediate project scope. The project develops a novel method for localization of earthquake damage and coalescence of fractures prior to a large earthquake, and quantifies different types of earthquake clusters with distinct productivity properties.
Exemplary Figure Figure 2

Premonitory localization of background events within Eastern Southern California. The times of the three largest (M > 7) earthquakes in the region are shown by vertical red lines. The time of the El Mayor-Cucapah event outside the examined region is shown by the vertical blue line. The analysis uses M > 3 background events, sliding time window of duration 2.5 years, and spatial cells with linear size 0.5 degrees. (a) Normalized proportion of occupied spatial cells. (b) Absolute localization of background earthquakes. Green horizontal lines emphasize increased (panel a) or decreased (panel b) values of the examined statistic prior to the large earthquakes.

Zaliapin, I. and Y. Ben-Zion (2020) Localization and coalescence of seismicity before large earthquakes. In review.