SCEC Award Number 16216 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Incorporating multi-segment ruptures into the composite source model
Investigator(s)
Name Organization
John Anderson University of Nevada, Reno
Other Participants
SCEC Priorities 6e, 6a, 6c SCEC Groups EEII, GMSV, GMP
Report Due Date 03/15/2017 Date Report Submitted 07/05/2017
Project Abstract
 The goal of this project is to implement multi-segment ruptures in the CSM. The code can incorporate the case where the fault consists of multiple adjoining segments that can be mapped onto continuous flat surface. The case that includes overlapping fault segments, branching, and other complex modes of multiple-fault participation needed new coding. This can be carried out for one case by running each segment separately and adding the seismograms with appropriate phase lags. The approach was tested for one case with overlapping segments of the San Jacinto fault. The northern Clermont segment and partly overlapping Casa Loma- segment were approximated with straight segments. For ruptures of these segments individually, the CSM parameter for subevent stress drop is found to contradict the PBRs when set to 60 bars, but to not contradict the PBRs when set to 20 bars. The same result holds for PBRs at Lovejoy Buttes that experienced the 1857 southern California earthquake on the San Andreas fault and for a throughgoing single rupture on the combined Clermont and Casa Loma segments. For rupture at random locations on the Clermont segment, the rupture on the Casa Loma segment was always triggered at the north end. Synthetics in this case appear more or less realistic, but have higher amplitudes that the other cases. Observations are needed to test this prediction.
Intellectual Merit This project begins the task of modeling realistic, multi-segment rupture earthquakes. A large outstanding problem is how to calibrate synthetic seismograms for earthquakes larger than any observed in southern California. The CSM is constrained to not topple precarious rocks that have undergone large earthquakes on nearby faults.
Broader Impacts  The method generates realistic synthetic seismograms that may be useful for engineering applications in cases where the engineer needs time series for conditions that are not available in the set of observed records.
Exemplary Figure Figure 3. Geometry: PBR tests. The map shows locations of modeled faults and of precariously balanced rocks (PBRs). The histograms, for each PBR, show how many realizations of the CSM source caused this rock to topple. From [#Brune:2016ab].