SCEC Award Number 12203 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title California Earthquake Rupture Model
Investigator(s)
Name Organization
David Jackson University of California, Los Angeles
Other Participants Kagan, Yan.
SCEC Priorities 2b, 4e, 2e SCEC Groups WGCEP, CSEP, EFP
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 We constructed a testable stochastic earthquake source model for intermediate- to long-term forecasts. The model is based on fundamental observations: the frequency-magnitude distribution, slip rates on major faults, long-term strain rates, and source parameter values of instrumentally recorded and historic earthquakes. The basic building blocks of the model are two pairs of probability density maps. The first pair consists of smoothed seismicity and weighted focal mechanisms based on observed earthquakes. The second pair corresponds to mapped faults and their slip rates and consists of smoothed moment-rate and weighted focal mechanisms based on fault geometry. We constructed from the model a “stochastic event set,” a large set of simulated earthquakes that are relevant for seismic hazard calculations and earthquake forecast development. Their complete descriptions are determined in the following order: magnitude, epicenter, moment tensor, length, displacement, and down-dip width. Our approach assures by construction that the simulated magnitudes are consistent with the observed frequency-magnitude distribution. We employed a magnitude-dependent weighting procedure that tends to place the largest simulated earthquakes near major faults with consistent focal mechanisms. Nevertheless, our stochastic model allows for surprises such as large off-fault earthquakes, events that comply with the observation that several recent destructive earthquakes occurred on previously unknown fault structures. We applied our model to California to illustrate its features.

Our paper entitled “A Stochastic Forecast of California Earthquakes Based on Fault Slip and Smoothed Seismicity” has been accepted for publication in the Bulletin of the Seismological Society of America in April, 2013.
Intellectual Merit Results include a forecast similar in many ways to the UCERF3 project, but our is much simpler and more easily testable.

By construction, our forecast fits the observed magnitude distribution and scaling relationships between magnitude, rupture length, down-dip width, and displacement.

Ours is the first forecast to include faults stochastically, recognizing that large earthquakes often occur near but not directly on mapped faults.
Broader Impacts Graduate education

The project funds supported a 10 week visit to UCLA by Stefan Hiemer, a graduate student at ETH, Zurich, Switzerland. Results and methods from the project will form a large part of Hiemer’s PhD dissertation. Anne Strader, a graduate student at UCLA, participated in discussion of the project and will use some project techniques in her PhD thesis.

Sharing results with user communities

Jackson presented and discussed project results at a scientific meeting hosted by Pacific Gas and Electric to review seismic safety provisions at the Diablo Canyon Nuclear Power Plant.

Jackson is a member of the core team developing the Uniform California Earthquake Rupture Forecast (UCERF-3). Some project results are used in the smoothed seismicity part of the UCERF forecast, and results from the project have played a significant part in planning discussions.

Jackson participated in workshops on global earthquake forecast models sponsored by the Global Earthquake Model (GEM) project at Ft. Collins, CO in August 2012, and at UCLA in January 2013. GEM is constructing a global model using smoothed seismicity and fault activity, for which our project results are applicable.

Hiemer participated in projects within the SHARE project (Seismic Hazard Harmonization in Europe). SHARE is constructing seismic hazard models in Europe based on active faults and smoothed seismicity using results of our project.

Sharing results with scientists outside SCEC

Jackson, Kagan, and Hiemer each presented results from the project at the 2012 meeting of the Seismological Society of America in San Diego, April 2012. This meeting is attended by scientists who construct probabilistic earthquake forecasts throughout the world and who could make use of our methods developed as part of the project.

Jackson discussed the scientific approach, methods, and results of the project at meetings of the Committee on Mathematical Geophysics of the International Union of Geodesy and Geophysics (Edinburgh, Scotland, June 2012); the workshop “Bridging the Gap: Mathematics in the Geosciences, at Princeton University in October, 2012.
Exemplary Figure Figure 2
Linked Publications

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