SCEC Award Number 13074 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Improvements and Applications of Earthquake Catalogs and 3-D Crustal Models to Advance Earthquake Predictability Research and SCEC Community Models
Name Organization
Egill Hauksson California Institute of Technology
Other Participants
SCEC Priorities 2, 2a, 2b SCEC Groups USR, EFP, Seismology
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
The December 14, 2012 Mw6.3 earthquake that occurred about 275 km west of Ensenada, Baja California, Mexico is evidence for continued tectonism in the eastern oceanic part of the Pacific plate. The preferred mainshock centroid depth of 20 km was located close to the bottom of the seismogenic thickness of the young oceanic lithosphere. The focal mechanism, derived from both teleseismic P-wave inversion and W-phase analysis of the mainshock waveforms, and the 12 aftershocks of M~3-4 are consistent with normal faulting on northeast striking nodal planes, which align with surface mapped extensional tectonic trends such as volcanic features in the region. The mainshock caused weak to moderate ground shaking in the coastal zones of southern California, USA and Baja California, Mexico but the tsunami was negligible.
In our stress drop study, we first remove the most obvious outliers in the dataset provided by Shearer et al. (2006), and correct for increasing rupture velocity with depth. Second we regress the median values of the stress drop against moment magnitude focal depth, crustal thickness, crustal density, heat flow, strain rate, and stress regime as projected onto each epicenter. We search for robust trends that may explain the contribution of these parameters to the changes in the median stress drops. We also identify spatial variations to facilitate the interpretation of the changes in median stress drops.
Intellectual Merit This project relates to many key SCEC objectives and will improve our understanding of earthquake activity across southern California. In particular, our high-resolution studies of seismicity provide better delineation of fault structures and make possible more advanced seismicity studies by us and other SCEC researchers. Our analyses provide fundamental insights into micro-earthquake activity, the crustal strain field, major faults, and crustal geophysics.
Broader Impacts The outreach activities consisted of publishing the results of the research in peer-reviewed journals. Also, the focal mechanism catalog is being distributed to researchers via the Southern California Earthquake Data Center (SCEDC). We have also presented results at SCEC workshops and E. Hauksson gave an oral presentation at a Northridge media event at Caltech, inJanuary 2014, and at the Northridge Symposium, UCLA, in January 2014.
Exemplary Figure Figure 3.
The map shows 80 years of seismicity (1932 to 2013) recorded by the Caltech/USGS Southern California Seismic Network; map courtesy of Dr. E. Hauksson, Caltech. Earthquakes in the magnitude range from 3.25 to 5.95 are shown as black circles, and of magnitude larger 5.95 are shown as red stars. The San Andreas fault is highlighted as a thick red line. The large seismicity clusters next to red stars are aftershocks.