Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

Verification and validation of the broadband CyberShake platform

Scott Callaghan, Christine A. Goulet, Fabio Silva, Philip J. Maechling, Robert W. Graves, Ossian O'Reilly, Kim B. Olsen, Albert R. Kottke, Yehuda Ben-Zion, & Te-Yang Yeh

Published December 13, 2021, SCEC Contribution #12632

The Southern California Earthquake Center (SCEC) has developed the CyberShake software platform to implement a physics-based probabilistic seismic hazard analysis (PSHA) approach using 3D wave propagation simulations to calculate seismograms and ground motions from sources defined in regional earthquake rupture forecasts. CyberShake has been used to calculate PSHA models for multiple regions in California, and is able to quantify effects such as 3D basin amplification and rupture directivity that are difficult to capture in conventional empirical ground motion models. Recently, CyberShake has been extended to generate broadband ground motions up to 50 Hz to include frequencies of engineering interest.

Broadband CyberShake has undergone an extensive verification and validation effort with the SCEC Broadband Platform (BBP) using historical earthquakes, including Northridge and La Habra. We have generated broadband CyberShake ground motions by combining deterministic finite difference wave propagation simulation results (≤1 Hz) with stochastic high-frequency results (1-50 Hz). We then compared the CyberShake ground motions to those computed with the BBP, which uses a frequency-wavenumber code for low-frequency content and a stochastic code for high-frequency content. We found close agreement in 1D simulations between the CyberShake and BBP results, for both Fourier amplitude spectra and pseudo-spectral accelerations across multiple sites.

We will present results from our CyberShake/BBP comparisons for multiple realizations of historical earthquakes from the BBP validation suite. We will describe how CyberShake components were configured to support BBP validation events. We also present comparisons of CyberShake models against recorded data, and propose modifications to CyberShake to improve its accuracy in modeling ground motions.

Key Words
probabilistic seismic hazard analysis, ground motion simulation, verification and validation

Callaghan, S., Goulet, C. A., Silva, F., Maechling, P. J., Graves, R. W., O'Reilly, O., Olsen, K. B., Kottke, A. R., Ben-Zion, Y., & Yeh, T. (2021, 12). Verification and validation of the broadband CyberShake platform. Oral Presentation at 2021 American Geophysical Union Fall Meeting.