SCEC Award Number 14208 View PDF
Proposal Category Workshop Proposal
Proposal Title Organizational Meetings for the SCEC Utilization of Ground-Motion Simulations Committee
Investigator(s)
Name Organization
Thomas Jordan University of Southern California C.B. Crouse URS Corporation
Other Participants UGMS Committee Members: Norm Abrahamson (PG&E/UCB), John Anderson (UNR), Bob Bachman (R.E. Bachman Consulting Structural Engineers), Jack Baker (Stanford), Jacobo Bielak (CMU), C.B. Crouse (URS) - Chair of Committee, Art Frankel (USGS), Rob Graves (USGS), Ron Hamburger (SGH), Curt Haselton (CSUC), John Hooper (MKA), Charlie Kircher (Kircher & Associates), Nico Luco (USGS), Farzad Naeim (J.A. Martin & Associates), Paul Somerville (URS)
SCEC Priorities 6e SCEC Groups EFP, GMP, SIV
Report Due Date 12/03/2014 Date Report Submitted N/A
Project Abstract
 The second UGMS meeting was held on May 12 at SCEC. Much of the meeting was devoted to a discussion of the CyberShake platform for generating ground-motion simulations throughout Southern California. T. Jordan first presented an overview of CyberShake and the SCEC ground motion simulation program. Jordan followed with presentations on the SCEC community velocity models, and comparisons of ground-motion predictions from CyberShake and the empirical NGA equations. Jordan also showed that Cybershake was able to reproduce long period ground motions from recent local earthquakes. Jordan’s final presentation was plans for future CyberShake development, which included extending the frequency band to 1.3 Hz to better define 1-sec period motions.

The UGMS affirmed that the long period mapping project will proceed on two parallel tracks, in which PSHA/DSHA will be conducted from the 3-D numerical simulations using CyberShake and from the traditional empirical approach using the NGA-West equations. It was agreed that the results from the 3-D simulations could be used to refine the equations ultimately used in the empirical approach. The second meeting concluded with an action item that SCEC would generate long period response spectra at selected sites using CyberShake and the NGA-West equations as a benchmark to guide the future direction of the committee.

Fourteen (14) sites were selected throughout Southern CA (see attached map) and risk targeted Maximum Considered Earthquake (MCER) response spectra were computed at each site by following the procedures in ASCE 7-10. Plots of the probabilistic and deterministic MCER response spectra, as well as the resulting MCER response spectra (lower of the probabilistic and deterministic MCER) were presented at the third UGMS committee meeting on November 3 at SCEC. Each plot showed the MCER response spectra from CyberShake and NGA-West. For some sites the two spectra were similar and at other sites significant differences were observed. The observations were discussed and suggestions for the third year research program were proposed.
Intellectual Merit The SCEC UGMS Committee is tasked to develop long-period response spectral acceleration maps for Los Angeles region for inclusion in NEHRP and ASCE 7 Seismic Provisions and in Los Angeles City Building Code. The maps would be based on 3-D numerical ground-motion simulations, and ground motions computed using latest empirical ground-motion prediction equations from the PEER NGA project. This project is coordinated with (1) the SCEC Ground Motion Simulation Validation Technical Activity Group (GMSV-TAG), (2) other SCEC projects, such as CyberShake and UCERF, and (3) the USGS national seismic hazard mapping project.
Broader Impacts The SCEC UGMS Committee is tasked to develop long-period response spectral acceleration maps for Los Angeles region for inclusion in NEHRP and ASCE 7 Seismic Provisions and in Los Angeles City Building Code. The maps would be based on 3-D numerical ground-motion simulations, and ground motions computed using latest empirical ground-motion prediction equations from the PEER NGA project. This project is coordinated with (1) the SCEC Ground Motion Simulation Validation Technical Activity Group (GMSV-TAG), (2) other SCEC projects, such as CyberShake and UCERF, and (3) the USGS national seismic hazard mapping project.
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