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Predictive Modeling of Seismicity Sequences in Southern California

Predictive Modeling of Seismicity Sequences in Southern California. Julia Clark David D. Bowman. California State University, Fullerton. Schematic Diagram of the Seismic Cycle. from Ellsworth et al. , 1981. Accelerating Seismicity Function. •Many current models of Accelerating Moment

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Predictive Modeling of Seismicity Sequences in Southern California

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  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 600 km 325 km 325 km 1952 Kern County Earthquake Bowman et al., 1998 RMS Residuals 200 km

  5. All California Earthquakes M≥6.51950-1995 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 Slipping Fault Slipping Fault Seismic Slip Seismic Slip Creep at Depth Calculate from motion on all adjacent faults plus creep at depth Future Earthquake

  9. Where are pre-earthquake stresses? Negative Slip Future Earthquake Creep at Depth =

  10. Bowman and King, 2001 Accelerating Seismicity in Stress Accumulation Regions

  11. Future California Earthquakes? No? Yes?

  12. Summer Project • Southern California • Faults • Fault Senerios • Coulomb Stress Region • Seismicity Analysis

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