The accommodation of distributed crustal strain across the northern Basin and Range on active faults: A paleoseismic study
Abstract
The Great Basin encompasses over two thirds of the Pacific/North American plate boundary and accommodates up to 25 percent of the relative plate motion by active faulting. Although the majority of the deformation within the Great Basin is concentrated along its margins, a small amount of geodetically measured strain is observed between the Central Nevada Seismic Belt and the Wasatch Front. In this area, comparison between short and long-term patterns of strain accumulation and release has been difficult due to slow deformation rates and insufficient paleoseismic data. Thus, we performed geologic studies along 10 rangefront faults distributed across US HWY 50 to document the amount and timing of late Pleistocene displacements. The data include geologic maps of Quaternary deposits and fault traces, paleoseismic trenches, scarp diffusion analyses, and soil characteristics in displaced alluvial surfaces. The observations are combined with paleoseismic information from previous studies to estimate a net long-term extension rate and compared to geodetic measurements. The results indicate that the rate of strain release recorded by faulting (about 1 mm/yr) over the late Pleistocene is, to first order, similar to the geodetic rate of strain accumulation. The agreement in extension rate estimates over different time scales implies that relatively slow extensional deformation has been operative in the Great Basin east of the Central Nevada Seismic Belt through the late Pleistocene. The geomorphic pattern of late Pleistocene ruptures characterized by left stepping enechelon strands with north easterly trends and a divergence of rupture orientations of about 20- 40 degrees from their respective range orientations may be the geomorphic expression of a component of right lateral shear within the interior of the Great Basin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.G21A0663K
- Keywords:
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- 1209 Tectonic deformation (6924);
- 7221 Paleoseismology (8036);
- 8002 Continental neotectonics (8107);
- 8109 Continental tectonics: extensional (0905)