SCEC Award Number 18062 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Relationships between Stress Drop, Directivity, and Ground Motions
Investigator(s)
Name Organization
Jeff McGuire Woods Hole Oceanographic Institution Yehuda Ben-Zion University of Southern California
Other Participants Haoran Meng, USC PhD student.
SCEC Priorities 1c, 1d, 4a SCEC Groups Seismology, FARM
Report Due Date 03/15/2019 Date Report Submitted 04/28/2019
Project Abstract
 We have completed the development of a catalog of second moment estimates for a dataset of ~30 Mw>3.5 earthquakes in Southern California using the approach we developed with SCEC funding. The new measurement approach which utilizes stacked Emperical Green’s Functions, results in many more observations of rupture duration per earthquake. We combine these measurements with a new inversion approach that specifically tests for minimum and maximum values of rupture area that are consistent with a given dataset. The resulting catalog shows systematic rupture directvitiy on some faults in Southern California as well as a tendency towards stress drops in the 10-50 MPa range.
Intellectual Merit This is the first systematic catalog of rupture area and directivity for moderate earthquakes in Southern California. The technique is novel in several respects. We think the observations will provide new constraints on rupture dynamics models both in terms of evaluating the bi-material effect and in terms of understanding the magnitude of static stress drops in moderate earthquakes.
Broader Impacts The project has supported USC graduate student Haoran Meng.
Exemplary Figure Figure 4. Directives in horizontal (a) and vertical (b) directions of analyzed target events shown in Figure 1. The arrows show the centroid rupture velocities. The colors denote the directivity ratio. (This is still on-going. There will be 30 events in total after this iteration of processing.). Figure Credit: Haoran Meng.