UCERF3 Fault-by-Fault Review Update

1. UCERF3 Fault-by-Fault Review Update • Tim Dawson (California Geological Survey and ExCom WGCEP) 2nd Workshop on Use of UCERF3 in the USGS National Seismic Hazard Map February 21, 2013 Menlo Park, CA

2. Purpose: Examine UCERF 3.2 results on a fault-by-fault section basis including: • Participation Magnitude Frequency Distributions (or recurrence interval vs magnitude for those that prefer), with comparisons to UCERF2. • Slip-rate and moment-rate values for both UCERF2 and UCERF3 (e.g., to understand whether earthquake rate changes are due to slip rate modifications or methodological differences). • 3D visualization of all ruptures that utilize the fault section (e.g., so we can see what's contributing, and how far multi-fault ruptures are stretching) • Recurrence interval maps • Review materials: http://wgcep.org/node/74

3. Meetings • Meeting #1: Menlo Park (1/24/2013) • Meeting #2: Pasadena (1/25/2013) • Meeting #3: Menlo Park (2/13/2013) • Meeting #4: Menlo Park (2/14/2013)

4. Participants • WGCEP ExCom: Ned Field, Tim Dawson, Tom Parsons, Ray Weldon • WGCEP Core: Glenn Biasi, Peter Bird, Karen Felzer, Dave Jackson, Kevin Milner, Morgan Page, Peter Powers, Yuehua Zeng • WGCEP SRP: Greg Beroza, Mike Blanpied, Bill Ellsworth, David Schwartz • WGCEP MOC: Tom Jordan, Chris Wills • Participants: • Bob Anderson (CEA) • Jack Boatwright (USGS) • Ben Brooks (USGS) • James Dolan (USC) • Tom Freeman (Geopentec) • Rob Graves (USGS) • Russ Graymer (USGS) • Jeanne Hardebeck (USGS) • Ruth Harris (USGS) • Suzanne Hecker (USGS) • Keith Kelson (URS) • Keith Knudsen (USGS) • Jim Lienkaemper (USGS) • Bill Lettis (LCI) • Bob McLaughlin (USGS) • David Oglesby (UCR) • Mark Petersen (USGS) • Carol Prentice (USGS) • Tom Rockwell (SDSU) • Kate Scharer (USGS) • Gordon Seitz (CGS) • Chesley Williams (RMS)

5. Fault-by-fault Review issues fell generally into two categories: • Issues that need immediate attention before running UCERF 3.3 • Issues that need attention for future versions of UCERF (UCERF4 and beyond). • Comments documented in compiled meeting notes, emails, and listed by fault section on excel table (will be eventually posted on website). • “No Show Stoppers” Identified

7. Primary Issues Identified: • Paleoevent rates are consistently low on SSAF. Geologists want UCERF model to better honor paleo-recurrence data (especially where it is robust, like at Wrightwood, Pallett Creek, Carizzo, Hog Lake, Tule Pond, etc.). • Issue is still open and will be discussed later today. Turn up weighting on paleoseismic data?

10. Primary Issues Identified: • Deformation Model Related: • ABM slip rates are consistently higher on block boundaries (and can been seen on hazard maps) • Proposed solution: Down weight ABM in weighting scheme

11. Primary Issues Identified: • Deformation Model Related: • Neokinema has some faults that are outside geologic bounds (generalized slip rate categories) • Proposed solution: Peter Bird has identified some faults that can be adjusted in Neokinema. In other cases, there are no quantitative geologic constraints and geodesy will be honored. • Highlights areas that may need additional examination by geologists and need for better ways to incorporate qualitative observations (geomorphology, geologic mapping) into models that use quantitative data).

12. Primary Issues Identified: • Deformation Model Related: • Zeng and Geologic Model • - Are categorical rates over-constraining Zeng model results? • Expand geological bounds for faults with categorical rates, see how much Zeng rates move?

13. Primary Issues Identified: • Fault Model Related: • Some geometries could use improvement • - Hayward – Calaveras junction • - Others listed on review comments table • Proposed solution: Hayward – Calaveras junction will be modified (needs to work with slip rates and location of paleoevent data). • Other faults tagged for UCERF4 improvements reavaluation

14. Primary Issues Identified: • Multi-fault rupture related: • Coulomb filter taking out rupture combinations that should be included • Proposed solution: List is being compiled (Kevin Milner, Morgan Page, Glenn Biasi all involved). These cases will be defined as exceptions in the model.

15. Primary Issues Identified: • Other major fault specific issues: • Big Lagoon: Fault stands out in hazard maps due to ABM (slip rate 8x higher than other models) • Proposed solution:. Issue with it being on block boundary in a complicated area (Gorda Plate/ Cascadia), sensitive to subduction zone coupling modeling. May need to hand modify (drop to geologic or average of other rates). • Contra Costa Shear Zone: Wide range of opinions expressed. • Proposed solution: No changes recommend. Weight-averaged slip rate is 1.1 mm/yr which is around what the geologists thought they could resolved.

16. Primary Issues Identified: • Other major fault specific issues: • Tolay: Geologists disagreed with representation in fault model (Representation based on outdated data). • Proposed solution: May need to be removed from fault model • Bennett Valley: Has high rate in NeoKinema with a low rate on the nearby Rodgers Creek Fault. Covariance with Rodgers Creek fault? • Proposed solution: Re-assign Bennett Valley rate to Rodgers Creek fault.