Analysis of Unusual Seismic Events and Constraints on the Active Tectonics and Rheology of the San Andreas Fault System: The Mendocino Triple Junction and Parkfield-Cholame, CA

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The proposed research will obtain a clearer picture of unusual events within the San Andreas Fault system and will use this information to gain a better understanding of the of active tectonics in California. The work will focus on two contrasting regions along the San Andreas Fault near the Mendocino Triple Junction and the Parkfield-Cholame segment of the fault. The researchers have found significant repeating earthquake activity in these areas and deep non-volcanic tremor activity. These phenomena will be characterized using the newly available continuous data recordings from the entire Northern California Seismic Network going back through 2000. This will allow a more accurate comparison between properties of tremors along transform and subducting plate boundaries. Auxiliary information from geodesy and from the seismicity patterns of more typical seismic events will also be used to constrain the analysis and interpretation of the results. Results from these activities have important implications for our understanding of active tectonics along the SAF plate boundary, and for understanding the role of deep fault zone rheology and deformation on earthquake occurrence. A comprehensive characterization and comparative analysis of the behavior of unusual events in contrasting tectonic regimes should also help increase our knowledge of deep fault zones in general.This project will produce catalogs of slow earthquake, tremor and repeating earthquake activity that do not currently exist. The proposed activity will also be a principal component of a graduate student's Ph.D. Thesis, and the results will be disseminated to the public through K-12 tours and annual public open houses of the Berkeley Seismological Lab. The projects activities will also benefit society by providing a greater understanding of the complex processes occurring in the Mendocino Triple Junction which is critical for the accurate assessment of the seismic hazard posed by the active tectonics of this region