SCEC Award Number 14047 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Collaborative proposal from UCSD and Caltech: SCEC Community Data Products of Relocated Seismicity, Improved Focal Mechanisms, and Waveform Spectra for Resolving Fine-Scale Fault Structures and State of Stress in Southern California
Investigator(s)
Name Organization
Peter Shearer University of California, San Diego Egill Hauksson California Institute of Technology
Other Participants
SCEC Priorities 2a, 2d, 2f SCEC Groups USR, SDOT, EFP
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 Our research represents the continuation of an ongoing and very successful collaboration between Caltech and UCSD to perform automatic processing of the SCSN waveform archive. Our SCEC work so far has focused on improving earthquake locations and focal mechanisms using waveform cross-correlation and S/P amplitude ratios, and on computing spectra for use in studies of earthquake source properties and attenuation. These results are described in many papers published in previous years (Hauksson and Shearer, 2005, 2006; Shearer et al., 2005, 2006; Lin et al., 2007a,b, 2008; Allmann et al., 2008; Lin and Shearer, 2009; Hauksson, 2010, 2011; Hauksson et al., 2012; Chen and Shearer, 2011, 2012; Yang et al., 2011, 2012; Hauksson, 2014). The latest version of our relocated catalog (the HYS catalog) contains high-precision locations of over 560,000 events from 1981 through 2014. Our previous catalogs, such as the LHS catalog by Lin et al. (2007b) have been widely used by other researchers, leading to new results on a number of topics, including earthquake triggering, swarms, locking depth, and earthquake scaling, which would not have been possible with standard catalogs. We also report on results of a newly created stress drop catalog for earthquakes between M1 and ~M3.5 with occasional events up to M5. The new catalog includes stress drops for more than 24,000 earthquakes between 2000 and 2014.
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 earthquake locations provide better delineation of fault structures and make possible more advanced seismicity studies by us and other SCEC researchers. Our stress drop analyses provide fundamental insights into the earthquake rupture process and the relationships between micro-earthquake activity, the crustal strain field, and major faults.
Broader Impacts Outreach activities consist of providing the relocated catalog to SCEC scientists and others doing research on seismicity in southern California. The relocated catalog is available at the Southern California Earthquake Data Center (SCEDC). We have also presented results at the SCEC workshop and E. Hauksson gave an oral presentation at the Northridge Symposium, UCLA, in January 2014.
Exemplary Figure Figure 3. (Exemplary Figure) Event locations from the HYS catalog (1981 – 2014). Similar-event clusters that have been relocated by using waveform cross-correlation are shown in black. Events in the SCSN catalog (and uncorrelated events in the other catalogs) are shown in brown. Events with M ≥ 5.5 are shown as stars. Faults are from Jennings (2010) with late Quaternary faults in shades of red (Hauksson et al. 2012).