Highlights from the Four Days of Meetings

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
Purpose: Examine UCERF 3.2 results on a fault-by-fault section
basis including:
1. Participation Magnitude Frequency Distributions (or recurrence interval vs
magnitude for those that prefer), with comparisons to UCERF2.
2. 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).
3. 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)
4. Recurrence interval maps
• Review materials: http://wgcep.org/node/74
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)
Ned Field, Tim Dawson, Tom Parsons, Ray Weldon
Glenn Biasi, Peter Bird, Karen Felzer, Dave Jackson, Kevin
Milner, Morgan Page, Peter Powers, Yuehua Zeng
Greg Beroza, Mike Blanpied, Bill Ellsworth, David Schwartz
Tom Jordan, Chris Wills
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)
Fault-by-fault Review issues fell generally into two categories:
1. Issues that need immediate attention before running UCERF
2. 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
“No Show Stoppers” Identified
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?
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
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).
Primary Issues Identified:
Deformation Model Related:
Zeng and Geologic Model
Are categorical rates over-constraining Zeng model
Expand geological bounds for faults with categorical rates, see
how much Zeng rates move?
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
Primary Issues Identified:
Multi-fault rupture related:
Coulomb filter taking out rupture combinations that should be
Proposed solution: List is being compiled (Kevin Milner, Morgan
Page, Glenn Biasi all involved). These cases will be defined as
exceptions in the model.
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
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.

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