SCEC Award Number 12034 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
Investigator(s)
Name Organization
Egill Hauksson California Institute of Technology
Other Participants Prof. Andreas Rietbrock, Liverpool University, UK
SCEC Priorities 2a, 2b, 2d SCEC Groups EFP, USR, Seismology
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 We apply new multi-taper spectral fitting methods to determine the long period end of S-wave spectra (sometimes called: signal moment) to calculate Mwsp magnitudes for small to moderate sized earthquakes M≤5.5. The new methods are optimized to provide a stable estimate of the value of the long period part of the spectra. Initially, we select a data set to invert for a geometrical spreading relationship for southern California and corresponding site effects for each station. We compare the Mwsp-corrections and ML-corrections with the independently determined Vs30 values available at most of the stations.

We have completed our project to invert for the state of stress in the southern California crust using a catalog of high quality earthquake focal mechanisms (1981-2010). The stress field is best resolved where seismicity rates are high and sufficient data are available to constrain the stress field across most of the region.
Intellectual Merit Earthquake predictability studies and earthquake interaction studies are only as good as the earthquake catalog that is being used. In particular, there is a need for stable magnitudes to determine the a-value and the b-value in the Gutenberg-Richter relationship as well as magnitude of completeness (Mc). As an example, Zechar and Jordan (2010) had to redo an earthquake forecast for Italy, because of issues with mixing Mw and ML magnitudes in the same catalog. This could have been avoided if one magnitude type had been available for all the earthquakes in their catalog.
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). E. Hauksson, The Goldilocks Seismicity of Southern California, (talk presented at AEG Southern California Section, Steven's Steak House in Commerce, 12 June 2012)
Exemplary Figure Figure 3. Composite image for SHmax orientation with overlapping G05N30 above G10N15 (in light color). The San Andreas Fault, Landers, Hector Mine, and El Mayor-Cucapah surface ruptures are highlighted in bold black lines. Black dashed lines mark two SHmax orientation transition lines: the Yucca-Imperial Valleys Line (YIV-L), and the Western Peninsular Ranges Line (WPR-L), respectively. “A”, “B” and “C” mark the three identified wedge-shapes (green dashed polygons). “D” marks isolated NNE SHmax area (green dashed polygon) along the San Jacinto Fault. “E” marks the Tehachapi Mountains stress heterogeneity. FF’, GG’, HH’ and II’ are four selected cross-sections with 0.2-degree in width and 300 km in length. The gray lines are postulated extensions of the WPR-L and the YIV-L as regional stress boundaries in southern California (Yang and Hauksson, 2013).
Yang, W. and E. Hauksson, The Tectonic Crustal Stress Field and Style of Faulting Along the Pacific North America Plate Boundary in Southern California, Geophys. J. Int., in review, March 2013.