SCEC Award Number 11052 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Seismicity of the Southern End of the M7.2 El Mayor-Cucapah Earthquake Sequence From Surface Wave Back-Projection
Investigator(s)
Name Organization
Jascha Polet California State Polytechnic University, Pomona
Other Participants Undergraduate students: 2 (likely to include Susana Lino)
SCEC Priorities A4, A11, A10 SCEC Groups Seismology, LAD, USR
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 The El Mayor-Cucapah earthquake sequence stretches from the Gulf of California to the border between Mexico and California and beyond. The seismicity of the southern part of the El Mayor-Cucapah aftershock zone and the area directly south of this zone is poorly covered by existing networks. To enhance our understanding of the tectonic framework of the El Mayor-Cucapah earthquake sequence and the seismicity preceding this event, a better earthquake catalog needs to be developed. As an initial step towards that goal, I have adapted a surface wave back-projection method that was originally developed for the analysis of global earthquakes, to detect and locate small earthquakes in the Northern part of the Gulf of California in the waveform data from the 2002-2007 temporary Baja network. Once the software was modified to allow for the analysis of small magnitude earthquakes in a regional setting, Cal Poly Pomona undergraduate student Amber Butcher analyzed several months of data to determine a preliminary magnitude calibration for the stacked amplitude, as produced by the algorithm, as compared to the magnitude of the events located by the RESNOM and global networks. This calibration shows more scatter than expected based on the results of our global study, but ISC and RESNOM magnitudes also vary significantly, and we are planning to investigate whether this scatter is due to the characteristics of the source or path effects. Further improvements will be implemented, such as tomographic travel time corrections and calculations of surface wave moment tensors for events greater than Mw3.5.
Intellectual Merit To enhance our understanding of the tectonic framework of the El Mayor-Cucapah earthquake sequence and the seismicity preceding this event, a better earthquake catalog needs to be developed. As an initial step towards that goal, I have adapted a surface wave back-projection method that was originally developed for the analysis of global earthquakes, to detect and locate small earthquakes in the Northern part of the Gulf of California and the ocean-continent transition region in the waveform data from the 2002-2007 temporary Baja network, that is available from the SCEC Data Center.
Broader Impacts Cal Poly Pomona undergraduate student Amber Butcher participated in this research project, by determining suitable back-projection parameters and analyzing several months of waveform data to detect and locate earthquakes. She has presented her research at two conferences.
Exemplary Figure Figure 2: Examples of several earthquakes located by surface wave back-projection.