SCEC Award Number 11169 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Seismic array back-projection and non-linear dynamic modeling of the El Mayor-Cucapah Earthquake
Investigator(s)
Name Organization
Jean Paul Ampuero California Institute of Technology
Other Participants Lingsen Meng, Alice Gabriel
SCEC Priorities A4, A7, A10 SCEC Groups Seismology, FARM, CDM
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 This project aimed at improving our understanding of the rupture process of the 2010 M7.2 El Mayor – Cucapah earthquake with two specific objectives. First, we aimed at obtaining new seismological constraints on the rupture process of this earthquake through back-projection source imaging based on array processing techniques applied to broadband seismic data recorded at regional distances by the SIEDCAR array in West Texas – Eastern New Mexico. We found seismological evidence for reverse rupture propagation towards the South in a fault segment North of the hypocenter. This is consistent with eyewitness reports of the rupture propagation through that area. The methods developed enabled analysis of other significant earthquakes (Haiti, Tohoku). Second, we aimed at providing an alternative interpretation of the asymmetric pattern of coseismic surface deformation inferred from remote sensing observations of this earthquake that does not require a fault geometry with opposite dips North and South from the hypocenter. Our alternative model involves the effect of the inelastic behavior of the crust (plastic strain) on the co-seismic deformation. We investigated fundamental aspects of the model through dynamic rupture simulations. Specifically, we determined how the contribution of plastic strain to the total seismic moment depends on the amplitude and orientation of the initial stress in 2D inplane simulations of pulse-like ruptures with off-fault plasticity. Other key source parameters were likewise characterized, including rupture speed and peak slip velocity.
Intellectual Merit We developed and applied advanced source imaging techniques to the study of an important earthquake near California. The study demonstrates the use of back-projection source imaging at regional distances. The technique reveals aspects of the rupture process that cannot be inferred with traditional source inversion approaches. The earthquake models developed here go beyond classical models by incorporating off-fault plastic deformation. Our thorough parametric study provides fundamental insight on this dynamic deformation mechanism and its importance.
Broader Impacts The project provided training and research opportunities for two graduate students in Caltech and a visiting graduate student from ETH Zurich. The source imaging technique developed here could be applied in almost real-time if regional data is available and has potential to contribute to the rapid response to future earthquakes in California.
Exemplary Figure Figure 1: Top left: kinematic source model of the El Mayor – Cuapah earthquake inferred by Wei et al (2012). Top right: location of the event hypocenter (red star), and SIEDCAR (green traiangles) and USArray (other triangles) stations used in our regional back-projection analysis. Bottom-left: normalized MUSIC pseudo-spectrum as a function of distance along-strike and rupture time. The warm colors indicate the location and timing of coherent source radiation. White lines indicate initial bilateral rupture. Gray line indicates reverse rupture propagation in the northern segment. Bottom right: sketch of a conceptual model of reverse propagation involving late rupture of a shallow asperity (Meng, Ampuero, Page and Hudnut).