Title: Fault zones big and small: Example geophysical investigations of faults in Southern California and the Pacific Northwest from local studies to community-wide collaborations
Abstract: The more we observe the more we discover that it is a volume of rock, a zone, and not a single simple fault plane that participates in major earthquake rupture. These zones contain clues of past behavior and, owing to their anomalous properties, influence future ruptures. Deeper investigations of fault zones worldwide are key to better understanding earthquake physics. I’ll present results on electromagnetic and seismic imaging efforts of a section of the Southern San Andreas fault zone. These works reveal a ~4 km deep <3 km wide fault zone conductor containing asymmetric low velocity damage with several northeast dipping features in the upper crust. At greater depth, the plate boundary manifests as a sharp change in electrical conductivity and pockets of high conductivity likely indicate ductile regions of strain and fluid accumulation. I’ll conclude this section with plans to expand this type of work throughout the Salton Trough. Looking Northwest, the implosion of part of Oregon State University’s football stadium provided an opportune moment to investigate a large seismic source in the near-field and image the poorly known local upper crust. The implosion equated to a magnitude 2.3 event and produced a non-uniform radiation pattern similar to an earthquake source. Its emitted waves and other passive seismic data highlighted the impact of Creek-derived wet attenuating sediments on the seismic wavefield and structure. The study also revealed the Corvallis fault zoneasa sharp seismic contrast that locates >300 m east of its current mapped location. Finally, I’ll introduce a recently funded NSF collaboratory called CRESCENT (Cascadia Region Earthquake Science CENTer). Led by 14 U.S. institutions, CRESCENT will be the nexus for earthquake research in the Pacific Northwest and will eventually include a global community working together on advancing subduction zone science. The center officially opens October 1st.
Zoom Link: https://gatech.zoom.us/j/95963290955
Recording: Zoom Recording