Mechanical and statistical aspects of brittle faulting: From coseismic rupture to cumulative deformation

This dissertation is focused on answering fundamental problems in extensional tectonics at Valles Marineris and Tempe Terra, two regions of Mars that have characteristics similar to continental rifts on Earth. Three-dimensional displacement-length scaling relations for terrestrial earthquakes are also investigated because they provide the underlying physical basis for the analyses of extensional tectonics on Mars.; Motivated by conflicting interpretations of the origin of blunt terminations of troughs at Valles Marineris, I investigate the reactivation of pre-existing cross faults in response to stress changes associated with slippage along a major, basin bounding normal fault (i.e., border fault). Observations from the Valles Marineris are consistent with model predictions, and are suggestive of a new sequence of deformation that accounts for the formation of blunt-trough terminations during the major phase of extension: coeval and locally bi-directional extension, that results from local stress field changes associated with border fault growth in a dominantly unidirectional remote strain field. These results indicate that irregular closed troughs at Valles Marineris are better interpreted as grabens rather than collapse depressions.; Rates of deformation at Tempe Terra are estimated through an analysis of fault population statistics, which incorporates fault segment linkage and utilizes displacement-length relationships from exposed normal faults in this region. Deformation remained localized within the Tempe Rift throughout much of Martian history, with moment rates, strain rates, and rifting velocities comparable to stable plate interiors of Earth. This indicates that either the timing of deformation on Mars is poorly constrained or, less likely, rates are significantly slower than on Earth.; Strike-slip earthquake source parameters, including slip distribution characteristics, are compared with predictions of a three-dimensional fracture mechanics model of faulting that accounts for cohesive end-zones (CEZ) near the fault tips and the aspect ratio (length/height) of the rupture surface. In this model, scatter between slip and rupture aspect ratio is related to differences in CEZ lengths, and model predictions are consistent with CEZ lengths estimated from 3-D slip distributions of four major earthquakes. The observations require large values of driving stress (∼100 MPa) and small stress drops (∼1 MPa), consistent with a partial stress drop model for earthquakes.