SCEC Award Number 19069 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
SCEC Priorities 1d, 1e, 3a SCEC Groups Seismology, EFP, CXM
Report Due Date 03/15/2020 Date Report Submitted 03/30/2020
Project Abstract
 The emphasis of this project has also been to produce and use the updated earthquake catalogs to address specific scientific research problems, such as fine-scale fault structures and rheological properties of the crust, and contribute to SCEC community models. In particular, we analyzed specific new earthquake sequences that are both of significant scientific and public interest.
We have maintained and updated our SCEC Community Products of refined earthquake locations and focal mechanisms for southern California, building on our previous SCEC work, which needed to be continued as more data accumulate and the methodology is improved.
During 2019, we further refined the earthquake locations and focal mechanisms. We updated our procedures by replacing the old location code with GrowClust developed by Trugman and Shearer (2017). The updated catalogs that extend from 1981 through 2019 include the first six months of the M6.4 and M7.1 Ridgecrest sequence. We have also used this catalog to analyze the seismotectonics of the Ridgecrest Coso region (Hauksson and Jones, 2020).
Intellectual Merit This work will provide a more detailed understanding of earthquake source properties and their temporal variations, which will contribute to the SCEC 3D velocity model, stress model, rheology model, and understanding of fault zone processes. In the case of a major earthquake, improved absolute and relative locations will provide rapid identification of the rupture planes. Further, more accurate hypocenters will facilitate detection and resolution of spatial migration in swarm activity, which will in turn contribute to SCEC community models such as the rheology model.
Broader Impacts Results of this research and development will also provide SCEC community products of refined hypocenter and focal mechanism catalogs. This effort will also bring SCEC closer to achieving the SCEC goal to use the same 3D velocity model for earthquake locations, focal mechanisms, ground motion predictions, numerous community models, as well as seismic source inversions for both point and finite sources.
Exemplary Figure Figure 2. Map and depth cross sections showing the depth distribution of seismicity, which is plotted on top of the three-dimensional Vp velocity model by Hauksson and Unruh (2007). Each aftershock is plotted as a black dot except the M≥5 events which are shown as stars. The A-cross section is parallel to the Mw7.1 mainshock rupture. The B through F cross sections are taken parallel to the Mw6.4 rupture. The 2019 surface ruptures are shown in white. ALFZ – Airport Lake fault zone; LLFZ – Little Lake fault zone; WHA – White Hills anticline; From Hauksson and Jones (2020).