SCEC Award Number 14181 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title The Parkfield patch and non-volcanic tremor in the San Andreas Fault
Investigator(s)
Name Organization
Abhijit Ghosh University of California, Riverside
Other Participants
SCEC Priorities 5a, 5d, 5e SCEC Groups Seismology, FARM, SDOT
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 A mini seismic array is installed at Cholame near the San Andreas Fault (SAF). It is located near the Parkfield patch that breaks repeatedly producing M6 earthquakes. In addition, the location is a suitable place to record tremor activity identified adjacent to the Parkfield patch. The array is installed in April 2013. SCEC funding enables me to run this array continuously till date, and I am thankful for that. This array is capturing tremor activity in great detail. It detects about 5 times more duration of tremor activity compared to existing seismic networks [Nadeau and Guilhem, 2009]. We imaged prolific tremor activity under Cholame and Parkfield. It appears that there are several patches that produce majority of the tremor. Fortuitously, we captured 2014 Mw 6.0 South Napa earthquake. Interestingly, tremor activity increased dramatically after the Napa earthquake. This high-resolution broadband array is providing a close look at the faulting activity at the San Andreas Fault near Parkfield.
Intellectual Merit This project studies the dynamics of the SAF near Parkfield. More specifically, it images the Parkfield patch that breaks quasi-periodically to produce M6 damaging earthquakes. The array records seismic radiation of a wide spectrum of fault motion – from regular microseismicity to tectonic tremor – which is critical to fully comprehend the different slip regimes, associated stress and their interaction. This study takes a step toward a better understanding of the complex issues of fault motion by using a well-designed mini-seismic array. It is providing us with the details of seismic activity of various flavors that may not be captured by standard seismic network.
Broader Impacts This work focuses on a fault patch in SAF that repeatedly produces damaging M6 earthquakes. Understanding how fault asperity works in this scale helps improve our estimates of seismic hazard in this area. In addition, this study explores at least two modes of fault slip, and the findings will help other branches of geosciences like, geodesy, tectonophysics, and rock physics to name a few. This project involves active participation of several undergraduate and graduate students. Through this project, they are able to get first-hand experience in cutting-edge seismology research. It helps a young scientist (the PI, Assistant Professor) build a quality research program in a minority serving institution (University of California, Riverside).
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