SCEC Award Number 22057 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Developing earthquake simulators for UCERF4
Investigator(s)
Name Organization
Bruce Shaw Columbia University
Other Participants
SCEC Priorities 5a, 4c, 5b SCEC Groups EFP, GM, FARM
Report Due Date 03/15/2023 Date Report Submitted 03/11/2024
Project Abstract
 With support from this SCEC grant, progress on a number of fronts related to earthquake simulators and next generation hazard models has been made. One area of progress involves using simulators to improve understanding of scaling relations relevant for use in fault-based seismic hazard. A second area of progress is in using simulator events as a guide in helping improve rupture plausibility filters to better estimate fault connectivity and rupture sets for use in UCERF4 and the 2023 NSHM. In the last year, two papers have been published on these topics. All have relevance to NSHM efforts. The first one (Milner, Shaw, and Field, 2022) was published in the Bulletin of the Seismological Society of America. The second one (Shaw, 2023) was published in the Bulletin of the Seismological Society of America. Below, some results from these papers are presented.
Intellectual Merit Earthquake simulators have the potential to contribute to our understanding of earthquake hazard and earthquake physics in a number of different ways. One way is in directly estimating earthquake rupture forecasts, which, when combined with ground motion models, give hazard estimates which compare very well with traditional statistical model estimates [Shaw et al., 2018]. This ability to replicate statistically based seismic hazard estimates by a physics-based model cross-validates standard methods and provides a new alternative approach needing fewer inputs and assumptions for estimating hazard. A second way is to use the models to help develop and constrain assumptions in the statistical models. Improving rupture sets using the simulators contributed in this way [Milner, Shaw, and Field, 2022]. A third way is to use the simulators as source models for ground motion studies [Milner, Shaw, et al., 2021]. All of these approaches help advance our understanding of hazard, and the potential underlying earthquake physics.
Broader Impacts The project contributes to improving seismic hazard estimates, which helps society better mitigate the hazards.
Exemplary Figure Figure 2: Aided NSHM effort through scaling relations study. (a) New refined approach subtracts off main trend and looks at deviations from that, plotting Magnitude residual δM=M − log10 A − 4.0 versus magnitude. Color is dip (black color is no dip information). Magenta line is mean residual averaged over magnitudes within 0.3 magnitude units on either side. Free surface effects and finite seismogenic width effects can be seen in looking at the residuals plot. This causes curvature in the data, makes fitting a straight line to the data problematic. From Shaw (2023). b) Best fitting slope of line using Wells and Coppersmith (1994) method to (Wells and Youngs, 2015) data shows best fitting slope depends on lower and upper magnitude cutoffs Mmin and Mmax. Difference from reference unity slope is plotted. From Shaw (2023)