Source characteristics of the foreshock sequence of the 2010 M7.2 El Mayor-Cucapah earthquake: implication for the triggering process

Xiaowei Chen, Qimin Wu, Dongdong Yao, & Zhigang Peng

Published August 15, 2019, SCEC Contribution #9895, 2019 SCEC Annual Meeting Poster #183

Foreshocks provide valuable information on the nucleation process of an upcoming large earthquake. However, the interpretation of foreshocks in terms of the underlying physical processes remains unresolved with two opposing end-member conceptual models: the cascade and the preslip models. In this study, we combine both frequency and time domain analyses to investigate the detailed source characteristics of the foreshock sequence of the 2010 M7.2 El Mayor-Cucapah earthquake, aiming to better understand the triggering process of the foreshock-mainshock sequence. For the larger foreshocks (M>3), we perform time-domain analysis to obtain finite source parameters. An iterative forward modeling method based on the empirical Green’s function (EGF) technique (Wu et al., 2019) is applied to retrieve relative source time functions (RSTFs), which are then used in directivity analysis and sub-event modeling. Preliminary results for the largest foreshock (M 4.3) show evidence for complex rupture process with multiple subevents. Ongoing RSTF analysis on smaller foreshocks will further delineate the distribution and evolution of the rupture processes of the foreshock sequence. In the frequency domain, we update the stacking based spectral analysis in Chen and Shearer (2013) with more waveform data made available from the Mexico’s Northwest Seismic Network (RESNOM), a more complete catalog of foreshocks (Yao et al., 2019) and an improved algorithm. The results will be used to validate previous observation of systematically lower average stress drops for the foreshocks (Chen and Shearer, 2013). Our combined time-domain and spectral results will shed light on the spatiotemporal evolution of the source properties and how the foreshock rupture processes influence fault activation and the triggering process of the earthquake sequence.

Citation
Chen, X., Wu, Q., Yao, D., & Peng, Z. (2019, 08). Source characteristics of the foreshock sequence of the 2010 M7.2 El Mayor-Cucapah earthquake: implication for the triggering process. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)