SCEC Award Number 11101 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Refining and Synthesis of 3D Crustal Models, and Seismicity Catalogs for Southern California
Investigator(s)
Name Organization
Egill Hauksson California Institute of Technology
Other Participants Wenzheng Yang, PostDoc
SCEC Priorities A4, A10, C SCEC Groups USR, Seismology, EFP
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 Using the HASH method (Hardebeck and Shearer, 2002, 2003), we calculate focal mechanisms for earthquakes that occurred in the southern California region from 1981 to 2010. A second project was the analysis of data from the Mw7.2 El Mayor-Cucapah mainshock that occurred on the 4th of April 2010 exhibited complex faulting, possibly starting with a ~M6 normal faulting event, followed ~15 sec later by the main event, which included simultaneous normal and right-lateral strike-slip faulting. We have also analyzed the relocated background seismicity (1981-2005), and several geophysical crustal properties to improve our understanding of the brittle part of the crust in southern California, often referred to as the seismogenic zone. In particular, the thickness of the seismogenic zone depends on crustal parameters such as presence of major late Quaternary faults, lithology, density, and tectonic strain rate.
Intellectual Merit This project analyzes data recorded by the Southern California Seismic Network (SCSN/CISN) to associate earthquakes with faults, estimate fault-scale seismicity parameters, determine the state of stress in the crust, and evaluate 3D-fault configurations in southern California. Further, we interpret the geophysical parameters in the context of geology and the spatial and temporal evolution of seismicity.
Broader Impacts The project has supported a PostDoc.
Exemplary Figure Figure 1. Map view of quality A focal mechanisms with around 13,000 earthquakes from the refined P wave first motion polarities and S/P amplitude ratios focal mechanism catalog (1981 - 2010). Focal mechanisms are plotted in the order of strike-slip (red), normal (green) and reverse (black). To each style of faulting, events are overlapped temporally. The sizes of beach balls are scaled with magnitudes with legend at the bottom left corner. Seismic stations are in blue triangles. Faults are in black curves. SBM, San Bernardino Mountain. The insert panel at the top right corner shows the relative location of the map area (red box) in the state of California. The San Andreas Fault in bold black curve separates the Pacific Plate and the North America Plate with arrows indicating relative motions.