SCEC Award Number 16168 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Comprehensive detections of foreshock sequences for large earthquakes around Southern California
Investigator(s)
Name Organization
Zhigang Peng Georgia Institute of Technology
Other Participants Dongdong Yao
SCEC Priorities 2a, 2b, 2c SCEC Groups Seismology, CS, EFP
Report Due Date 03/15/2017 Date Report Submitted 04/25/2017
Project Abstract
 We relocate the foreshock sequence of the 2010 Mw7.2 El Mayor-Cucapah Earthquake by combining stations in both Southern California Seismic Network (SCSN) and Red Sísmica del Noroeste de México (RESNOM). Additionally, ~74 events from both catalogs are used as templates to scan through the con-tinuous waveforms starting from 21 days before up to the mainshock to detect possible missing events. Currently, ~450 events are detected and we find nearly continuous episodes of foreshock sequence. Two intensive bursts of seismicity can be observed on March 21st and within last 48 hours immediately before the mainshock. The burst within last 48 hours showed swarm-like behavior, with the largest M4.3 event occurred 24 hours before the mainshock. On the other hand, the burst on March 21st started with a M3.9 event, and continued with several M3+ earthquake sequences. The spatial-temporal pattern of the foreshock activity suggest that the earthquake swarm immediately before the mainshock occurred in a smaller region surrounding the mainshock epicenter, while seismicity 2 more days earlier were located across a broader area. We did not observe any clear migration or accelerating behavior before the 2010 El Mayor-Cucapah mainshock.
Intellectual Merit This project contributes to a better understanding of nucleation process of the 2010 Mw7.2 El Mayor-Cucapah mainshock, and an improved foreshock catalog for this sequence. It also has implications in earthquake forecasting and hazard mitigation.
Broader Impacts This project supported an international summer intern Sizuang Deng (from USTC, now in UT Austin) to conduct research at Georiga Institute of Technology in Summer 2015. The remaining funding is used to support summer research of a graduate student Dongdong Yao in summer 2016. It also supported international collaborations with Dr. Raul Castro from CICESE in Mexico.
Exemplary Figure Figure 3. (a) Magnitude versus time for all detected foreshocks (color-coded by the cross-correlation values). (b) A zoom-in plot showing the swarm-like sequence within last 48 hours before the mainshock.