Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

L.B. Christiansen; Shaul Hurwitz; Steven E. Ingebritsen

doi:10.1029/2006gl028634

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Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

L.B. Christiansen·Shaul Hurwitz·Steven E. Ingebritsen

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Abstract

We analyze seismic data from the San Andreas Fault (SAF) near Parkfield, California, to test for annual modulation in seismicity rates. We use statistical analyses to show that seismicity is modulated with an annual period in the creeping section of the fault and a semiannual period in the locked section of the fault. Although the exact mechanism for seasonal triggering is undetermined, it appears that stresses associated with the hydrologic cycle are sufficient to fracture critically stressed rocks either through pore‐pressure diffusion or crustal loading/unloading. These results shed additional light on the state of stress along the SAF, indicating that hydrologically induced stress perturbations of ∼2 kPa may be sufficient to trigger earthquakes.

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Geophysical Research Letters Article

Source-reported bounding extent: 35.478200079045834° to 36.45406645165268° latitude; -121.38955997594803° to -119.6894256986042° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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L.B. Christiansen, Shaul Hurwitz, Steven E. Ingebritsen. 2007-02-23. Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA. https://doi.org/10.1029/2006gl028634

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