A SCEC CyberShake Physics-Based Probabilistic Seismic Hazard Model for Northern California
Abstract
The Southern California Earthquake Center (SCEC) has developed CyberShake, a simulation platform that performs physics-based probabilistic seismic hazard analysis (PSHA) using 3D deterministic wave propagation simulations. The CyberShake PSHA calculations begin by simulating time- and space-varying of Strain Green Tensors. An earthquake rupture forecast (ERF) is then extended by varying hypocenters and slips on finite faults, generating hundreds of thousands of events per site of interest. Seismic reciprocity is used to calculate synthetic seismograms for each event at each site, which are processed to obtain intensity measures (IMs) such as RotD50 spectral acceleration. These IMs are combined with ERF probabilities to produce hazard curves. PSHA results from hundreds of locations across a region are interpolated to produce hazard maps. In 2018 SCEC performed CyberShake Study 18.8, which produced a physics-based PSHA hazard model for a large Northern California region that includes the San Francisco Bay Area. PSHA calculations were performed up to 1 Hz for 869 locations in Central and Northern California using the NCSA Blue Waters and ORNL Titan supercomputers. To support simulation volumes which included most of California, we tiled three separate SCEC 3D Community Velocity Models into a composite statewide velocity model and applied smoothing along interfaces to minimize reflection and refraction artifacts. To improve representation of near-surface velocity structure in the tomographically-derived models, we applied the Ely (2010) method for generating a geotechnical layer (GLT) in the top 300 meters based on values from the Wills (2015) Vs30 map. This computational effort enabled the calculation of a continuous physics-based PSHA map for a large portion of California, obtained by combining results from multiple CyberShake studies. We will present our new hazard results for a variety of sites and discuss the impacts of including a GTL and the consideration of background seismicity on the overall hazard estimates.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.S43D0642M
- Keywords:
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- 7294 Seismic instruments and networks;
- SEISMOLOGY