Presentation
Evaluating Temporal Variations in Fault Slip-Rate and Fault Interaction in the Eastern California Shear Zone
American Geophysical Union, Fall Meeting
(2008)
Abstract
Delineating spatiotemporal patterns of strain accumulation and release within plate boundaries remains fundamental to our understanding of the dynamics of active crustal deformation. The timescales at which active strain varies or remains constant for individual fault systems, however, are often poorly resolved. The origin of large-magnitude strain transients in the Eastern California shear zone remains enigmatic and underpins the importance of quantifying active deformation at multiple geologic timescales along this tectonic boundary. Here, we focus on the Late Pleistocene- Holocene record of slip on the NW-striking Little Lake fault zone, one of the primary structures responsible for transferring Pacific-North American plate motion between the northern Mojave Desert and the east side of the Sierra Nevada block north of the Garlock fault. Discrepancies between geologic and geodetically determined rates of motion along the Little Lake fault zone in the China Lake-Indian Wells Valley area suggest a potentially complex temporal history of slip on this structure with some slip stepping eastward onto structures bounding the west side of the Coso Range. Preliminary reconstruction of a slip-rate history on the Little Lake fault from multiple generations of displaced Quaternary geomorphic features suggests potential variation in fault-slip rates at timescales of 104- 105 years. Two paleochannel margins on a basalt strath in the Little Lake spillway represent the youngest of these features. Each margin exhibits ~30 m of right-lateral displacement and suggests a minimum slip rate of ~1.4 mm/yr during Holocene-Late Pleistocene time. Additionally, a prominent fluvial escarpment or terrace riser along the east side of Little Lake wash is offset at least ~150 to 700 m, depending on how the initial geometry of this feature is reconstructed. Pending geochronologic constraints on the age of this feature, such an offset potentially suggests higher rates of slip averaged over longer timescales.
Keywords
- Fluvial,
- Strike-slip,
- Continental tectonics,
- Landscape evolution
Disciplines
Publication Date
December, 2008
Location
San Francisco, CA
Citation Information
C. B. Amos, A. Jayko and R. Burgmann. "Evaluating Temporal Variations in Fault Slip-Rate and Fault Interaction in the Eastern California Shear Zone" American Geophysical Union, Fall Meeting (2008) Available at: http://works.bepress.com/colin-amos/23/