SCEC Award Number 17218 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Developing earthquake simulators for use in seismic hazard estimates: Contributing to OEF, CISM, and UCERF4
Investigator(s)
Name Organization
Bruce Shaw Columbia University
Other Participants
SCEC Priorities 5a, 5b, 3a SCEC Groups WGCEP, CSEP, EFP
Report Due Date 06/15/2018 Date Report Submitted 11/10/2018
Project Abstract
 Seismic hazard models are important for society, feeding into building codes and hazard mitigation efforts. They, however, rest on many uncertain assumptions and are difficult to test observationally due to the long recurrence times of large earthquakes. Physics-based earthquake simulators offer a potentially helpful tool, but themselves face a vast range of fundamental scientific uncertainties. We compare a physics-based earthquake simulator against the latest seismic hazard model for California. Using only uniform parameters in the simulator we find strikingly good agreement of the long-term shaking hazard compared with the California model. 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.
Intellectual Merit The replication of the statistical UCERF3 hazard model by a physics-based model provides a strongly increased confidence in long term seismic hazard estimates through a triangulation by very different methods, and a new tool for understanding its origins and robustness. It also provides a new method for estimating hazard needing fewer inputs and assumptions.
Broader Impacts We have found remarkable robust agreement between statistical and physics-based models for hazard measures of
central engineering interest. These include PGA, and PSA from 0.2-1 seconds, at $10^{-3}$ to $10^{-5}$ annual probability levels, which includes much of the realms upon which building codes are based. Replication of long-term seismic hazard coming from two very different approaches, a form of triangulation \citep{munafo18}, with one approach a more traditional statistical method, and one a new physics-based simulator method, provides an important cross-validation and increased confidence in our ability to estimate values of these societally important quantities. It offers as well a new tool needing fewer inputs and assumptions for estimating long-term seismic hazard.
Exemplary Figure Figure 1: Maps of shaking hazard in earthquake simulator compared with UCERF3 hazard model, and plots of differences. Immediate predecessor UCERF2 California hazard model is shown for comparison. Maps show PGA 2% in 50yr exceedance. Units are in fractions of the acceleration of gravity g. (A) UCERF2. (B) UCERF3. (C) RSQSim model. (D) Map of ln ratio of ucerf2/ucerf3 shaking hazard. (E) Map of ln ratio of simulator/ucerf3 shaking hazard. Note that the simulator is even closer to UCERF3 than UCERF3 is to UCERF2. Figure from [Shaw, et al., 2018]
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