Predictive Modeling of Seismicity Sequences in Southern California

1
Predictive Modeling of Seismicity Sequences in
Southern California
Julia Clark David D. Bowman
California State University, Fullerton
2
Schematic Diagram of the Seismic Cycle
from Ellsworth et al., 1981
3
Accelerating Seismicity Function
Many current models of Accelerating Moment
Release fit seismicity data to an analytic
function
One of the most commonly used functions is the
Power-Law time-to-failure equation Bufe
and Varnes (1993) Sornette and Sammis (1995)
This function takes the form e(t ) A -
B(tf-t)m
Where e(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
4
Selecting a circular region
1952 Kern County Earthquake
Bowman et al., 1998
RMS Residuals
200 km
5
All California Earthquakes M6.51950-1995
Bowman et al., 1998
6
Critical Regions
Circular Regions A simple systematic method to
calculate critical regions using an arbitrary
shape that is easy to program, but is not based
on geology.
A New Method The 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.
7
What is Coulomb Stress Change?
From King et al., 1994
8
Stress Change From Loading a Locked Patch on a
Simple Fault
Calculate from motion on all adjacent faults plus
creep at depth
Future Earthquake
9
Where are pre-earthquake stresses?
Future Earthquake
Creep at Depth

10
Accelerating Seismicity in Stress Accumulation
Regions
Bowman and King, 2001
11
Future California Earthquakes?
No?
Yes?
12
Summer Project

• Southern California
• Faults

• Fault Senerios

• Coulomb Stress Region

• Seismicity Analysis