Conveners: Ned Field and the Working Group on California Earthquake Probabilities
Dates: June 4, 2011
Location: Embassy Suites Mandalay Beach, Oxnard, CA

In 2009, the Working Group on California Earthquake Probabilities (WGCEP) was funded to provide an update to the Uniform California Earthquake Rupture Forecast (UCERF3). The project is jointly sponsored by the U.S. Geological Survey (USGS), California Geological Survey (CGS), and the Southern California Earthquake Center (SCEC) and partially supported under a SCEC contract with the California Earthquake Authority (CEA). Among other goals, UCERF3 aims to incorporate space geodetic constraints into a new assessment to be completed by mid-2012. A subgroup was formed to undertake this task and forge a consensus on space geodetic results that could be confidently applied to UCERF3 goals.

With support from both SCEC and CEA this activity was initiated in 2010. The activities included a 2-day workshop in April 2010, which resulted in (1) an assessment of secure science ready for UCERF3 applications within the next year; and (2) an agenda of new research objectives for SCEC, USGS and others in support of UCERF3 and related probabilistic seismic hazard assessments. For more detail, see the workshop report or Eos article published in September 2010 (Hearn et al., 2010).

A wrap-up workshop is planned for June of 2011. The goal is to present provisional plans for submission of geodetic estimates of slip rates on major California faults and strain rates in the surrounding blocks to UCERF3 and solicit comments and guidance from the space geodetic community. This input will be used by GPS/UCERF3 steering committee to draft three disciplinary reports, assemble slip and strain rate estimates, and submit to the UCERF3 Scientific Review Panel (SRP) by late 2011 for advice and comment.

Workshop Format: Topical sessions to discuss main science issues and participants’ solutions to test problems. Session chairs (co-conveners plus a few others) will be charged with organizing topical sessions and summarizing results for wrap-up presentation and workshop report.

Main scientific topics in which provisional UCERF3 reports will be presented will include:

        Strain Rate Map Methodologies and Issues

• Presentation and quantitative evaluation of strain rate models of California (~16 research groups); Discussion of best practices for developing strain rate models

• Discussion and examples of dividing strain into elastic earthquake cycle strain and inelastic strain in crustal blocks

• Discussion and recommendations on how strain rate estimates can be used in UCERF3

        Earthquake Cycle Deformation and Influence of Postseismic Transients

• Discussion of recommendations to make to WGCEP regarding how to consider time-dependent deformation in UCERF3

        Block Models and GPS Fault Slip Rate Estimation

• Results from community modeling exercise with standard block model geometry and GPS input data will be summarized (likely participants include Peter Bird, Rob McCaffrey, Kaj Johnson, Yuehua Zeng, Bill Hammond, and perhaps others)

• Discussion will focus on how to reconcile differing GPS slip rate and locking depth estimates and the recommendations to make to the WGCEP