Understanding the time-varying deformation field of plate bounding fault zones at great depth is important for understanding active tectonics, fault-fault interactions and the occurrence of large earthquakes. However, measurements of large-scale time-varying deep deformation along vertical strike-slip plate boundaries such as the San Andreas Fault have been difficult to obtain, due to the limited extent, coverage and sampling frequency of geodetic measurements and the fundamental trade-offs and assumptions required to infer deep deformation on vertical faults from measurements of surface motion.
To more clearly understand the role of deep transient deformation along the San Andreas Fault (SAF) plate boundary in central California, data from new seismic indicators of deep fault zone deformation are analyzed and compared to geodetic measurements of deformation and moderate to large earthquake occurrence. The new seismic indicators are of two types: 1) characteristically repeating microearthquakes (used to inferred deep-fault aseismic slip information) and 2) deep non-volcanic tremor activity (indicators of episodic slow-slip events in the deep sub-seismogenic lithosphere).
This project will produce a large-scale catalog of tremor activity along 175 km of the central SAF that does not currently exist and that will likely be of use for related research. The proposed activity will also comprise a component of a graduate student's Ph.D. dissertation and will be a major component of an undergraduates senior thesis. Results will be disseminated to the public through K-12 tours and annual public open houses of the Berkeley Seismological Lab and to the scientific community scientific community at meetings and in publication . Results will also be incorporated into an upper-division undergraduate course on California Earthquakes (eps 130). Two undergraduates are also participating in the preliminary and ongoing research through an independent research course (eps 199). Project activities will benefit society through public education, education and training of students and by providing information on the complex processes occurring along the SAF plate boundary and the timevarying aspects of slip-deficit accumulation in the region, all of which are critical inputs for the accurate assessment of the seismic hazard posed by the active tectonics of this region.
