Paleoseismic and Geologic Data for Earthquake Simulations

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Paleoseismic and Geologic Data for Earthquake
Simulations

• Lisa B. Grant and Miryha M. Gould

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Overview

• Paleoseismic data is needed to understand and
  simulate long time scale, multi-cycle fault
  behavior for predictive simulation
• Uncertainty in paleoseismic observations is a
  major challenge for data assimilation
• Existing paleoseismic databases for hazard
  calculations should be modified for predictive
  simulations
• Paleoseismic data can identify areas for
  predictive simulations of fault interactions

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Primary Objective of the ACES Science Plan

• to develop physically based numerical
  simulation models for the complete earthquake
  generation process and to assimilate observations
  into these models at all time and space scales
  relevant to the earthquake cycle (Mora, ACES
  Proceedings 2000).

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Significance of Geologic Data

• Fault data provides framework for simulations
• Paleoseismic data is required for modeling
  multi-cycle rupture behavior

San Andreas fault (courtesy of J R. Arrowsmith)
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Paleoseismic DataDescribes pre-instrumental
earthquakes

• Site specific geologic investigations
• Data sets are small, sparse and analog
• Quantification of uncertainty is a major
  challenge for data assimilation
• Existing paleoseismic databases for probabilistic
  seismic hazard assessment include
• Direct measurements
• Interpreted parameters

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Direct Measurements and Interpreted Data

• Site specific (point) measurements
• Date of last rupture
• Dates of multiple ruptures
• Average recurrence interval
• Surface displacement
• Slip rate

• Fault segments and segment properties (spatially
  averaged)
• Characteristic recurrence interval
• Magnitude
• Rupture extent
• Slip distribution

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Example Fault Database from California (CDMG)
(visualization by Peggy Li)
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San Andreas Fault, California
(courtesy of J R. Arrowsmith)
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Fault Segments
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Slip Rates (mm/yr) By Segment
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Slip Rates (mm/yr) at Measurement Sites
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Per Segment
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Average Recurrence Interval (years)
At Measurement Sites
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1600 year Southern San Andreas Fault Earthquake
Dates and Interpreted Rupture History
New data sites
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Paleoseismology of the San Andreas Fault System
Bulletin Seismological Society of AmericaEdited
by Grant, Lettis and Schwartz

• Dedicated Issue
• Expected late 2002
• New sites
• Additional data and reduced uncertainty at
  existing sites

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A Northward Propagating Earthquake Sequence in
Coastal Southern California?
L. B. Grant and T. K. Rockwell, in press, SRL
Example of using paleoseismic data to identify
potentially hazardous areas for predictive
simulation
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Deformation and Fault Slip Rates in S.
California From Geodetic and Paleoseismic
Measurements
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Coulomb Stress Change Model
(Stein et al. Science, 1994)
Suggests northern Newport-Inglewood fault is
close to failure
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Questions for Predictive Simulation - Is this a
northward propagating rupture sequence? - When
will the northern Newport-Inglewood Fault Zone
rupture?
Dates of Most Recent Rupture from Paleoseismic
Research
S. California Coastal Fault Zone
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Conclusions

• Paleoseismic data is needed to understand and
  simulate long time scale, multi-cycle fault
  behavior for predictive simulation
• Uncertainty in paleoseismic observations is a
  major challenge for data assimilation
• Existing paleoseismic databases for hazard
  calculations should be modified for predictive
  simulations
• Paleoseismic data can identify areas for
  predictive simulations of fault interactions

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The End