Comprehensive Analysis of the 2010 Mw 7.2 El Mayor-Cucapah Foreshock Sequence

Date: 4/25/2019

Time: 09:30 AM

Room: Cascade I

Large earthquakes can sometimes be preceded by foreshocks, while the exact relationship between foreshocks and mainshock nucleation is still unclear. Here we conduct a comprehensive analysis of the 2012 Mw7.2 El Mayor-Cucapah foreshock sequence, including detection of small missing foreshocks, refined relocations and source parameter analysis. We used 66 relocated foreshocks listed in the SCSN catalog as templates, and applied the template-matching technique to continuous recordings within 150km epicentral distances starting from 21 days prior to the mainshock until the main event. 550 additional events were detected, and the results indicated nearly continuous foreshock sequence, with two most intensive bursts around March 21^st and within last 2 days prior to the mainshock. By fitting the detected foreshock sequence using the Epidemic Type Aftershock Sequence (ETAS) model, we found that the first active burst around March 21^st fits the mainshock-aftershock type sequence, while the other one within last 2 days before the mainshock exhibits swarm-like behavior. We also identified the potential timing issues of the EHZ component at certain stations during this time period, and compared the different detection results with or without those stations. Additionally, we selected master and empirical Green’s function (EGF) pairs based on both relative locations and waveform similarity. Source areas and stress drops were then estimated using the spectral ratios of master and EGF pairs. By closely examining the spatio-temporal evolution and source parameters of the foreshock sequence from a more complete template-matching catalog, we are aiming to better understand the evolution of the foreshock sequence and its role in the mainshock nucleation.

Presenting Author: Dongdong Yao

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