Dynamics of the Sierra Nevada block and implications for western U.S. fault mechanics and continental geodynamics
Abstract
We present geodynamic modeling of the Sierra Nevada block to constrain the magnitude and origin of forces driving continental deformation at the Pacific-North American plate boundary in the western United States. The relative influence of Pacific plate shear, collapse of the high potential energy continental interior, and the importance of crustal block interaction on stress transfer in the lithosphere remain uncertain and debated largely because it is difficult to separate these processes when we do not know well the distribution of lithospheric strength (e.g., Jackson, 2002). Our physically based numerical modeling, constrained by observations of lithospheric stress, offers three primary conclusions. First, shear stress owing to relative Pacific-North American motion exists within the Basin and Range province and is at least in part responsible for the deformation there. Second, the vertically integrated shear stress on the San Andreas fault changes dramatically along strike, by as much as a factor of 10, indicating fault strength can evolve with accumulated offset or structural simplicity. Third, the Sierra Nevada block is compressing into the Oregon forearc with a vertically integrated stress of 3.0 ± 0.3 TN/m, driving it to the north and causing N-S compression and shortening. This indicates crustal block interaction is an important mechanism of stress transfer in lithospheric dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.S54A..02F
- Keywords:
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- 8111 Continental tectonics: strike-slip and transform;
- 8118 Dynamics and mechanics of faulting (8004);
- 8120 Dynamics of lithosphere and mantle: general (1213);
- 8164 Stresses: crust and lithosphere