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Predictive Modeling of Seismicity Sequences in
Southern California
Julia ClarkDavid D. Bowman
California State University, Fullerton
•Many current models of Accelerating Moment Release fit seismicity data to an analytic function
Accelerating Seismicity Function
• One of the most commonly used functions is the
Power-Law time-to-failure equationBufe and Varnes (1993); Sornette and Sammis
(1995)
Where (t) is the seismic energy release at time t, tf is the time of the earthquake, and A,B and m are fitted parameters describing the shape of the function
• This function takes the form:
(t ) = A - B(tf-t)m
325 km
600 km
325 km
RMS Residuals
200 km
1952 Kern County EarthquakeSelecting a circular region
Bowman et al., 1998
Critical Regions
Circular RegionsA simple systematic method to calculate critical regions
using an arbitrary shape that is easy to program,but is not based on geology.
A New MethodThe idea is to model critical regions as the region of stress
accumulation before an earthquake.
Stress Accumulation Regions• The stress field from loading a locked fault patch is the same as the stress field created by slipping the fault backwards.• This permits us to calculate the Coulomb Stress Change for the future earthquake, and look for accelerating seismicity in the regions of increased stress.
Slipping Fault Slipping FaultSeismic Slip Seismic Slip
Creep at Depth
FutureEarthquake
Calculate from motion on all adjacent faultsplus creep at depth
Stress Change From Loading a Locked Patch on a Simple Fault