SCEC Award Number 13019 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 Xiaowei Chen, graduate student
SCEC Priorities 2a, 2d, 2f SCEC Groups Seismology, USR, SDOT
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 This research represents the very successful collaboration between Caltech and UCSD to perform automatic processing of the Southern California Seismic Network (SCSN) waveform archive. Our SCEC work has focused on improving earthquake locations using waveform cross-correlation, and on computing spectra for use in studies of earthquake source properties and attenuation. These results are described in many papers published during the last four years (Allmann et al., 2008; Chen et al. 2012; Chen and Shearer, 2011, 2013; Hauksson, 2010, 2011, 2014; Hauksson et al., 2012, 2013; Hauksson and Shearer, 2005, 2006; Lin et al., 2007a,b, 2008; Lin and Shearer, 2009; Shearer et al., 2005, 2006; Shearer and Lin, 2009; Shearer, 2012; Yang et al., 2012; Yang and Hauksson, 2011, 2013).

The latest version of our relocated catalog (the HYS catalog) contains high-precision locations of over 550,000 events from 1981 through 2013. Our previous catalogs, such as the LHS catalog by Lin et al. (2007b) have been used by a number of other researchers, leading to new results that would not have been possible with standard catalogs. For example, the debate over the relative importance of static versus dynamic triggering of aftershocks has been informed by our catalogs (Felzer and Brodsky, 2006; Richards-Dinger et al., 2010), Vidale and Shearer (2006) identified many distinctive characteristics of earthquake swarms in southern California, Davidsen et al. (2006) found new statistical features of seismicity with unexpected scaling properties, Shearer and Lin (2009) identified Mogi-doughnut behavior in seismicity preceding small earthquakes, Tape et al. (2009) used the LSH locations in the starting model for their recent adjoint tomography study of the southern California crust, Smith-Konter et al. (2011) used the catalog to estimate locking depths for major fault segments, and Yang and Hauksson (2013) used the relocated earthquakes and the focal mechanisms to determine the state of stress across southern California.
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 Caption for Exemplary Figure 4.
Event locations from the HYS catalog (1981 – 2013). Similar-event clusters that have been relocated using waveform cross-correlation are shown in black. Events in the SCSN catalog (and uncorrelated events in the other catalogs) are shown in yellow. Events with M ≥ 5.5 are shown as stars. Faults are from Jennings (2010) with late Quaternary faults in shades of red and early Quaternary in blue (Hauksson et al. 2012).