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

Geophysical Research Letters
By: , and 

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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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA
Series title Geophysical Research Letters
DOI 10.1029/2006GL028634
Volume 34
Issue 4
Year Published 2007
Language English
Publisher AGU
Contributing office(s) Volcano Hazards Program
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