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Tectonic stressing in California modeled from GPS observations
J. Geophys. Res., Vol. 111, B03407, doi:10.1029/2005JB003946, 2006
[Printable article (5.0 Mb)]
Tom Parsons
U.S. Geological Survey, Menlo Park, CA
Non-technical summary: For the past ~20 years, repeated GPS (Global Positioning System) measurements have tracked the slow, incremental motions of the Earth's crust in California across the Pacific-North American plate boundary. These accumulated motions add stress to the crust that eventually manifests as earthquakes. In this study a detailed numerical model of the state of California was developed to calculate the rate of stress growth in the crust. The model broke the large region into small pieces called finite elements to enable the complex problem to be solved. It is shown by the model that stress growth is highest across a ~200-km-wide band that includes the San Andreas fault, and that corresponds to where most M>4 earthquakes have occurred. Detailed variations in calculated stressing rates will enable large earthquake recurrence intervals to be calculated.
Figure caption. Example of the meshed upper crustal volume shown with 10X vertical exaggeration so that topographic relief is evident. Black lines show boundaries of variable tetrahedral mesh, which is finer in areas of greatest detail. The average element size is roughly 5 5 km. Shaded relief contouring, fault lines, and the study area box are draped onto the model for location purposes.
