| This thesis addresses the state of stress in continental lithosphere, the mechanisms by which it is maintained, and its implications for the mechanical behavior of plate-bounding faults and the accommodation of tectonic deformation.; Measured stress magnitudes in intraplate brittle crust are consistent with the Coulomb frictional-failure criterion and coefficients of friction similar to those determined in laboratory experiments, implying that the upper crust is in a state of frictional equilibrium. If the lower portions of the lithosphere deform ductilely, then the lithosphere as a whole is in a state of failure and its strength must equal the magnitude of any applied tectonic forces. We use this inference to consider the vertical distribution of lithospheric strength and the bounds this places on intraplate strain rates.; Using earthquake focal mechanism stress inversions, we have mapped the horizontal stress field in central and southern California and verified previous suggestions that the San Andreas fault (SAF) slips in response to lower levels of shear stress than anticipated on the basis of the intraplate or laboratory observations. By comparing the stress results with geodetic data and dynamic modeling results, we further show that while crustal velocities adjacent to the SAF are consistent with localized plate kinematics, crustal stresses seem to be controlled by relatively far-field processes.; Finally, by amalgamating data from three independent seismographic networks, we have produced an improved Japanese focal mechanism catalog with which to investigate the stresses associated with subduction and crustal collision. The axis of maximum horizontal compressive stress in central and southwestern Japan is found to be approximately parallel to the axis of maximum contractional strain rate once deformation associated with an elastic model of subduction thrust locking has been subtracted from the original strain rate observations. This suggests that the state of stress in the Japanese arc is related more to long-term relative plate motions than to interseismic strain accumulation and seismogenic release on the subduction thrusts. |
