Recent changes in stress regime in the Walker Lane Zone
- Geological Survey, Menlo Park, CA (United States)
- Univ. de Paris Sud, Orsay (France)
The NW-trending Walker Lane Zone (WLZ) is located along the western boundary of the northern Basin and Range province and the Sierra Nevada. This zone is distinguished from the surrounding Basin and Range province on the basis of irregular topography and evidence for both strike-slip and normal late Cenozoic faulting. Inversion of slip-vectors on active faults, historic fault offsets, and earthquake focal mechanisms indicate two distinct Quaternary stress regimes within the WLZ, both of which are characterized by a consistent WNW [sigma]3 axis: a normal faulting regime with a mean [sigma]3 axis of N100[degree]E and a stress ratio, R, (R=([sigma][sub 2][minus][sigma][sub 1])/([sigma][sub 3][minus][sigma][sub 1])) of 0.65, and a younger strike-slip faulting regime with a mean [sigma][sub 3] axis of N115[degree]E and an R value of 0.19 (R=0 indicates stress regimes transitional between strike-slip and normal faulting), which is compatible with historic fault offsets and earthquake focal mechanisms. New slip data in Plio-Quaternary deposits together with cross-cutting dip-slip and strike-slip striae on fault surfaces in Pleistocene volcanic rocks support previous results from Owens Valley that indicate a roughly constant WNW [sigma][sub 3] axis during a distinct change from extensional tectonics to strike-slip tectonics that may have occurred in Late Pleistocene time. The location of the WLZ between deep-seated extension of the Basin and Range and right-lateral strike-slip tectonics of the San Andreas fault zone is probably responsible for the complex interaction of tectonic regimes in this transition zone. Dating of geologic evidence is too poor to determine if there has been a single recent absolute change in stress magnitude or if there is an alternating or cyclic variation.
- OSTI ID:
- 5126581
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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