Vertical deformation associated with normal fault systems evolved over coseismic, postseismic, and multiseismic periods

Autor: Tom Parsons, George A. Thompson
Rok vydání: 2016
Předmět:
Zdroj: Journal of Geophysical Research: Solid Earth. 121:2153-2173
ISSN: 2169-9313
DOI: 10.1002/2015jb012240
Popis: Vertical deformation of extensional provinces varies significantly and in seemingly contradictory ways. Sparse but robust geodetic, seismic, and geologic observations in the Basin and Range province of the western United States indicate that immediately after an earthquake, vertical change primarily occurs as subsidence of the normal fault hanging wall. A few decades later, a ±100 km wide zone is symmetrically uplifted. The preserved topography of long-term rifting shows bent and tilted footwall flanks rising high above deep basins. We develop finite element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. We replicate observations with a model that has a weak upper mantle overlain by a stronger lower crust and a breakable elastic upper crust. A 60° dipping normal fault cuts through the upper crust and extends through the lower crust to simulate an underlying shear zone. Stretching the model under gravity demonstrates that asymmetric slip via collapse of the hanging wall is a natural consequence of coseismic deformation. Focused flow in the upper mantle imposed by deformation of the lower crust localizes uplift under the footwall; the breakable upper crust is a necessary model feature to replicate footwall bending over the observed width (
Databáze: OpenAIRE
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