SCEC Award Number 14053 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Developing earthquake simulators for use in seismic hazard estimates
Name Organization
Bruce Shaw Columbia University
Other Participants
SCEC Priorities 2e, 4e, 2b SCEC Groups WGCEP, FARM, CSEP
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
This project proposal arose from an effort to contribute further to an understanding of fault system geometry and dynamics on it, with an aim towards developing simulators for use in the next generation UCERF efforts.
The two main thrusts were developing simualtors that can handle UCERF3 fault geometries, and extending the class of geometries and loading conditions they can handle.
Work examining the role that complex stranded geometries
play in fault system dynamics was initiated,
with interesting preliminary results obtained.
Four main results from this work are:
(1) The development of earthquake simulators running UCERF3
fault geometries.
(2) The exploration of alternaitive loading mechanisms
going beyond backslip loading, with remote loading and
self-organized slip partitioning simulators running
UCERF3 fault geometries achieved.
(3) The development of multistranded fault geometries which
deterministically generate aftershocks.
(4). The finding that aftershocks in the deterministic
models show reduced stress drops for nearby aftershocks,
giving a physical basis for empirical findings of GMPE's.
Intellectual Merit This research aims to develop a line of earthquake simulators capable of being usefully applied to earthquake hazard problems at the UCERF scale. It seeks to do this by developing a line of physics-based simulators able to
interact with the UCERF infrastructure, including assimilating UCERF fault system geometries,and outputting fault based event sequences which can be read by UCERF tools
and projected onto data metrics used in current UCERF inversions. It also has been exploring the development of physical models of aftershock generation, for application to next generation Operational Earthquake Forecasts.
Broader Impacts Developed new finding which can be used in OEF.
Exemplary Figure Figure 4.
Lower median stress drops for nearby aftershocks
relative to mainshocks in model.
(a) Mean stress drops averaged over rupture area
as a function of magnitude.
Red circles are averages for individual mainshocks,
blue circles are averages for individual nearby aftershocks.
The blue circles tending to lie below the red circles at a given magnitude indicates the apparent differences in the statistics of the populations. Solid lines show averages for a given magnitude of the two populations, with yellow showing mainshocks and cyan showing nearby aftershocks.
(b) Physical origin for the lower mean stress drops of nearby aftershocks. The effect comes from rerupturing of mainshock area which has rehealed less, and thus has lower dynamic strength drop. Plot shows friction drop versus initial friction value, averaged over source area for individual events. Colors show average of log of state variable. The blue points in the lower left show events which have been stuck for a shorter time and thus tend to have a lower strength drop when they rerupture relative to the parts of the fault which have been stuck a long time, shown in red points.