WGCEP Workshop

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WGCEP Workshop What Represents Best Available
Science in terms of Time-Dependent Earthquake
Probabilities? Introduction by Ned Field
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Best Available Science?

• Poisson Model (long-term rates)
• Quasi-Periodic Recurrence Models
• BPT Renewal
• Time or Slip predictable
• Static-Stress Interaction Models
• Clock change
• BPT-step
• Rate State
• Clock change w/ Rate State
• Hardebeck (2004) approach
• Empirical Rate Change Models
• Clustering Models
• Foreshock/Afershock statistics (e.g., STEP ETAS)

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(No Transcript)
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Summary (in brief) of Previous
Working Groups on California Earthquake
Probabilities (WGCEP, 1988, 1990, 1995, 2002)
They generally segmented faults and applied
elastic-rebound-theory-motivated (quasi-periodic)
renewal models to define time-dependent
earthquake probabilities ...
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Reids (1910) Elastic Rebound Hypothesis
Stress Loading
Stress Loading
Stress Loading
Stress Loading
EQ
EQ
EQ
EQ
Time
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Reids (1910) Elastic Rebound Hypothesis
Perfectly Periodic
more noisy system
Lognormal or BPT distribution
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WGCEP 1988
They divided the San Andreas, San Jacinto,
Hayward, and Imperial Faults into segments and
assumed each ruptures only in a single-magnitude
(characteristic) earthquake.
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WGCEP 1988

• COVI 0.2
• Mean Recurrence Interval
• from
• Ave of those observed previously.
• Slip in last event divided by slip rate.
• Ave slip divided by slip rate.

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WGCEP 1990
Updated WGCEP (1988) for San Francisco Bay Area
in light of the 1989 Loma Prieta earthquake (and
some new data).
e.g., applied a clock change to account for
influence of Loma Prieta on Peninsula segment
(seg 3).
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WGCEP 1995
Focused on southern Cal. (SCECs Phase II report).
Innovations
2) Allowed neighboring segments to sometimes
rupture together as cascade events
3) Included lesser faults and background
seismicity (to account for unknown faults)
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WGCEP 1995
Problem predicted twice as many mag 6-7 events
as have been observed historically, which led to
a lively debate on this apparent earthquake
deficit
Need to allow huge events (Mag8) potentially
anywhere (Jackson, 1996)
But such events would leave obvious
scars (Schwartz, 1996 Hough, 1996)
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WGCEP 1995
Problem predicted twice as many mag 6-7 events
as have been observed historically, which led to
a lively debate on this apparent earthquake
deficit
Note these two were part of the working group
implying a lack of consensus
Need to allow huge events (Mag8) potentially
anywhere (Jackson, 1996)
But such events would leave obvious
scars (Schwartz, 1996 Hough, 1996)
Problem results from several factors solution
exists (e.g., Stirling and Wesnousky (1997)
Stein Hanks (1998) and Field et al., (1999))
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WGCEP 2002
Focused on Bay Area
Other Innovations
2) Consensus process rather than consensus
model 3) Extensive treatment of epistemic
uncertainties (logic-tree branches)
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Current Working Group on California Earthquake
Probabilities (WGCEP) Development of a Uniform
California Earthquake Rupture Forecast (UCERF)
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22 of our funding comes from the California
Earthquake Authority (CEA)
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California Earthquake Authority (CEA)
Northridge caused 93 of insurers to halt or
significantly reduce coverage. CEA was created
(via state legislation) to resolve the
crisis. CEA is a privately financed, publicly
managed (and tax exempt) organization that offers
basic earthquake insurance for California
homeowners and renters. Its governed by CA
Governor, Treasurer, Insurance Commissioner,
Speaker of the Assembly, and Chairperson of the
Senate Rules Committee. CEA policies are sold
only through participating insurance companies
(two-thirds of California homeowners policies).
Policies carry a 15 deductible. Today the CEA
has 7.2 billion to pay claims. CEA is required
by law to use best-available science.
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Best Available Science?
California Insurance Code section 10089.40 (a)
"Rates shall be based on the best available
scientific information for assessing the risk of
earthquake frequency, severity and
loss. Scientific information from geologists,
seismologists, or similar experts shall not be
conclusive to support the establishment of
different rates unless that information, as
analyzed by experts such as the United
States Geological Survey, the California Division
of Mines and Geology, and experts in the
scientific or academic community, clearly shows a
higher risk of earthquake frequency, severity, or
loss between those most populous rating
territories to support those differences.
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Seismic Event
Seismic Event means one or more earthquakes
that occur within a 360-hour period. The seismic
event commences upon the initial earthquake, and
all earthquakes or aftershocks that occur within
the 360 hours immediately following the initial
earthquake are considered for purposes of this
policy to be part of the same seismic event.
from page 6 of CEAs Basic Earthquake
Policy--Homeowners doc
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WGCEP Goals
To provide the California Earthquake Authority
(CEA) with a statewide, time-dependent ERF that
uses best available science and is endorsed by
the USGS, CGS, and SCEC, and is evaluated by a
Scientific Review Panel (SRP), CEPEC, and NEPEC
Coordinated with the next National Seismic Hazard
Mapping Program (NSHMP) time-independent
model This will be used by CEA to set earthquake
insurance rates (they want 5-year forecasts,
maybe 1-year in future)
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SCEC will provide CEA with a single-point
interface to the project.
WGCEP Organization Funding Sources
CEA
Geoscience organizations
SCEC
NSF
Management oversight committee
Scientific review panel
USGS Menlo Park
USGS
MOC
SRP
Sources of WGCEP funding
USGS Golden
Bill Ellsworth (chair) Art Frankel David
Jackson Steve Wesnousky Lloyd Cluff Allin
Cornell Mike Blanpied David Schwartz
Thomas H. Jordan (SCEC, Chair) Rufus
Catchings (USGS, Menlo Park ) Jill McCarthy
(USGS, Golden ) Michael Reichle (CGS)
CGS
State of CA
WGCEP ExCom
Working Group on California Earthquake
Probabilities
Working group leadership

Ned Field (USGS, Chair) Thomas Parsons (USGS,
Menlo Park) Chris Wills (CGS) Ray Weldon (U of
O) Mark Petersen (USGS, Golden) Ross Stein
(USGS, Menlo Park)
Subcom. A
Subcom. B
Subcom. C

Task-oriented subcommittees
Plus many others
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Delivery Schedule

• February 8, 2006 (to CEA)
• UCERF 1.0
• S. SAF Assessment to CEA
• Aug 31, 2006 (to CEA)
• Fault Section Database 2.0
• Earthquake Rate Model 2.0 (preliminary for
  NSHMP)
• April 1, 2007 (to NSHMP)
• Revised Earthquake Rate Model 2.x
• (for use in 2007 NSHMP revision)
• September 30, 2007 (to CEA)
• UCERF 2 (reviewed by SRP, NEPEC, and CEPEC)

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Important Lessons from Previous WGCEPs

• Everything takes longer than you expect
• Some planned on innovations wont pan out
• Focus on whats important
• There will be problems with the final model
• The best time to solve these problems is right
  away (while fresh in the mind)
• Burnout makes this problematic

• Thus
• Plan for both the near and long term (e.g., build
  a living, adaptive, extensible infrastructure)

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Deploy as extensible, adaptive (living) model
i.e., modifications can be made as warranted by
scientific developments, the collection of new
data, or following the occurrence of significant
earthquakes. The model can be living to the
extent that update evaluation process can occur
in short order. How do we plan to achieve this?
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UCERF Model Components (generalization of
WGCEP-2002)
Fault Model(s)
Black Box
Deformation Model(s)
Black Box
Earthquake Rate Model(s)
Black Box
Earthquake Prob Model(s)
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Object Oriented (Modular) Framework - building on
OpenSHA
The computer code
The models /or applications
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UCERF Model Components (generalization of
WGCEP-2002)
Fault Model(s)
Black Box
Deformation Model(s)
Black Box
Earthquake Rate Model(s)
Black Box
Earthquake Prob Model(s)
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UCERF Model Components
Fault Model(s)
Black Box
Instrumental Qk Catalog
Deformation Model(s)
Fault Section Database
Historical Qk Catalog
Black Box
Earthquake Rate Model(s)
GPS Database
Black Box
Paleo Sites Database
Earthquake Prob Model(s)
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UCERF Model Components
Fault Model(s)
Object Oriented (Modular) Framework
Black Box
Deformation Model(s)
Black Box
Earthquake Rate Model(s)
Makes logic trees very easy to handle
Black Box
Earthquake Prob Model(s)
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OpenSHA Hazard Curve Calculator
WGCEP-2002 Hazard Curves (Field et al.
2005, SRL) Distributed Object Technologies
(Maechling et al., 2005, SRL)
Now w/ NGAs ERM 2.2 also
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Issue with Logic Trees

• They take time and resources to implement and
  document
• Must be careful about correlations (Page and
  Carlson, 2006, BSSA)
• Is anyone using them?
• How do we know which are important or worth
  pursuing (especially in terms of loss)?

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Demo Loss Calculator?
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Logic Trees
What we need is not all possible branches, but
the minimum number of branches that span the
range of viability and importance
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Best Available Science?

• Poisson Model (long-term rates)
• Quasi-Periodic Recurrence Models
• BPT Renewal
• Time or Slip predictable
• Static-Stress Interaction Models
• Clock change
• BPT-step
• Rate State
• Clock change w/ Rate State
• Hardebeck (2004) approach
• Empirical Rate-Change Models
• Clustering Models
• Foreshock/Afershock statistics (e.g., STEP ETAS)