Investigating Fault Rupture Connectivity Between Upper-plate Faults and the Southern Cascadia Subduction Zone: A Paleoseismic Investigation of the Little Salmon Fault Zone, Hydesville, California
Abstract
Along southern Cascadia, strain accumulation is coupled between the subducting Gorda slab and the overriding upper-plate. However, the role of upper-plate faults in accommodating strain along the southern Cascadia subduction zone (SCSZ) is uncertain. To test competing hypotheses— whether upper-plate faults are kinematically linked or independent to the SCSZ—we performed a paleoseismic study within the central segment of the Little Salmon Fault (LSF), the principal upper-plate structure within the SCSZ. Previous paleoseismic studies on the western segment of the Little Salmon Fault zone (LSF) document large displacements per earthquake (3.5 to 4.5 meters dip slip) and at least three earthquakes within the last 2,000 years, indicating the possibility the LSF may be kinematically connected with the SCSZ and rupture in concert. Here, we present results from two fault-normal paleoseismic trenches excavated across a previously unstudied portion of the LSF and the Goose Lake Fault (GLF). Our trenching efforts focused on documenting event chronology, displaced or folded stratigraphy, slip indicators, and local fault geometry. Our pending event chronology, determined using radiocarbon (AMS) and/or optical stimulated luminescence (OSL) dating methodologies, will be compared with 1) SCSZ paleoseismic history, 2) the western segment of the LSF event record, and 3) Goose Lake Fault event chronology record. Collectively, we can draw inferences whether the LSF may rupture concurrently with the SCSZ, the western segment of the LSF, and the GLF. Our results provide important implications into seismic hazards presented by upper-plate structures in the SCSZ and whether or not these shallow crustal structures are independent seismic sources.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T31G0355L
- Keywords:
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- 7221 Paleoseismology;
- SEISMOLOGY;
- 8107 Continental neotectonics;
- TECTONOPHYSICS;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS