EGU2020-5625, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-5625
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seismic reflection imaging of the low-angle Panamint Valley normal fault system, eastern California, USA

Ryan Gold1, William Stephenson1, Richard Briggs1, Christopher DuRoss1, Eric Kirby2, Edward Woolery3, Jack Odum1, and Jaime Delano1
Ryan Gold et al.
  • 1United States Geological Survey, Geologic Hazards Science Center, Denver, Colorado, United States of America (rgold@usgs.gov)
  • 2Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, Oregon, United States of America
  • 3University of Kentucky, Earth and Environmental Sciences, Lexington, Kentucky, United States of America

A fundamental question in seismic hazard analysis is whether <30º-dipping low-angle normal faults (LANFs) slip seismogenically. In comparison to more steeply dipping (45-60º) normal faults, LANFs have the potential to produce stronger shaking given increased potential rupture area in the seismogenic crust and increased proximity to manmade structures built on the hanging wall. While inactive LANFs have been documented globally, examples of seismogenically active LANFs are limited. The western margin of the Panamint Range in eastern California is defined by an archetype LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high-angle dextral-oblique normal faults displace mid-to-late Quaternary alluvial fans near the range front. To image shallow (<1 km depth), crosscutting relationships between the low- and high-angle faults along the range front, we acquired two high-resolution P-wave seismic reflection profiles. The northern ~4.7-km profile crosses the 2-km-wide Wildrose Graben and the southern ~1.1-km profile extends onto the Panamint Valley playa, ~7.5 km S of Ballarat, CA. The profile across the Wildrose Graben reveals a robust, low-angle reflector that likely represents the LANF separating Plio-Pleistocene alluvial fanglomerate and pre-Cambrian meta-sedimentary deposits. High-angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high-angle faults vertically displace the LANF up to 70 m within the Wildrose Graben. Similarly, the profile south of Ballarat reveals a low-angle reflector, which appears both rotated and displaced up to 260 m by high-angle faults. These results suggest that near the Panamint range front, the high-angle faults are the dominant late Quaternary structures. We conclude that, at least at shallow (<1 km) depths, the LANF we imaged is not seismogenically active today.

How to cite: Gold, R., Stephenson, W., Briggs, R., DuRoss, C., Kirby, E., Woolery, E., Odum, J., and Delano, J.: Seismic reflection imaging of the low-angle Panamint Valley normal fault system, eastern California, USA, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5625, https://doi.org/10.5194/egusphere-egu2020-5625, 2020

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