CyberShake models of seismic hazards in Southern and Central California

Thomas H. Jordan, & C Others

In Preparation November 30, 2017, SCEC Contribution #7994

CyberShake is a high-performance computational platform developed by the Southern California Earthquake Center (SCEC) for producing seismic hazard models from large suites of earthquake simulations. Code optimization and the development of workflow tools on the NCSA Blue Waters and OLCF Titan supercomputers have substantially reduced the computational costs of the CyberShake runs. A recent workflow efficiently utilized both machines to generate 285 million two-component seismograms for the central California region from which 46 billion intensity measurements were extracted. We apply the averaging-based factorization (ABF) method of Feng & Jordan (2014) to decompose current ensemble of 12 CyberShake models into a seismological hierarchy comprising site, path, directivity, and source complexity effects. CyberShake simulations with the Graves & Pitarka (2007, 2010, 2014) rupture generators show how the strength of the directivity effect decreases with increasing source complexity, and simulations with the SCEC Community Velocity Models show how the site and path effects vary with differences in upper crustal structure, and they are particularly instructive about epistemic uncertainties in the modeling of basin effects. Comparisons quantified by the ABF variances of the CyberShake models indicate that simulation-based hazard models can potentially reduce , the total unexplained variability in the GMPEs, by about one-third, which would modify the site-specific exceedance probabilities at high shaking intensities by orders of magnitude.

Citation
Jordan, T. H., & Others, C. (2017). CyberShake models of seismic hazards in Southern and Central California. Proceedings of the 11th National Conference in Earthquake Engineering, (in preparation).