SCEC Award Number 17044 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title SCEC Community Data Products of Earthquake Catalogs with improved Focal Depth Estimation, for Resolving Fine-Scale Fault Structures and Crustal Rheology in Southern California
Investigator(s)
Name Organization
Egill Hauksson California Institute of Technology
Other Participants Chunquan Yu - Postdoc - California Institute of Technology
SCEC Priorities 1d, 3a, 4a SCEC Groups EFP, CXM, Seismology
Report Due Date 06/15/2018 Date Report Submitted 06/12/2018
Project Abstract
 For a decade UCSD and Caltech have worked on improving earthquake locations and focal mechanisms, and systematically estimating stress drops from source spectra. Our results have produced a large improvement in earthquake location accuracy for small earthquakes and dramatically sharpened seismicity features in southern California, while providing insight into fault zone processes (see Figure 1). We have also produced large catalogs of focal mechanisms and Brune-type stress drop estimates, which have facilitated large-scale analyses of the stress state of the southern California crust. This work has led to a substantial body of published results, both by our group and by others who have used our data products in their own research.
During 2017, we further refined earthquake locations and focal mechanisms. We paid special attention on improving focal depths, as well as hypocentral absolute and relative error estimates. We developed two complementary methods for determining absolute and relative earthquake depth, and applied them to the 2010 El Mayor-Cucapah earthquake sequence. Building on our previous SCEC work, we also maintained and updated our SCEC Community Products of refined earthquake locations and focal mechanisms for 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 focal mechanism catalogs and 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 SCEC workshops.
Exemplary Figure Figure 1. The HS catalog (1981 – 2017). 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 red stars. Faults are from Jennings and Bryant (2010) with late Quaternary faults in shades of red and early Quaternary in blue. Credit: Hauksson et al., (2012).