Microseismotectonics of the Coso Volcanic Field, Eastern California

The near ubiquitous occurrence of microearthquakes and hydrothermal activity is fortunate because it serves to highlight the principles and practices of seismotectonics in the Coso Volcanic Field, Eastern California. Seismotectonics is the analysis of crustal deformation with the locations and mechanisms of the earthquakes it produces. Earthquakes are extremely sensitive indicators of the state of stress, because they occur on hydraulically conductive faults that are optimally oriented for failure. The microearthquake kinematics are determined with respect to the state of stress and provide the the basis of the seismotectonic interpretation.; The seismotectonic investigation is facilitated with a new stress inversion technique. The state of stress is constrained with a triaxial representation of the Coulomb-Navier failure criterion. The failure criterion and the state of stress are used to distinguish the fault kinematics from the earthquake focal mechanisms. Evaluation of the Coulomb-Navier failure conditions requires a knowledge of the absolute magnitudes of tectonic stress.; The absolute stress magnitudes are constrained by a relationship between the depth of the earthquake the state of stress. The first part of the dissertation is devoted to obtaining accurate earthquake locations to properly estimate of the hypocentral depth. A new earthquake location algorithm is developed to account for the strong geological and geophysical constraints placed on the velocity structure. In the second part, the focal mechanisms are calculated with respect to the constraints on the velocity model and are input into the new stress inversion technique. The microearthquake kinematics are highly consistent with shear failure and provide an important verification of seismotectonic tenets.; The resulting state of crustal stress and strain are consistent with the combined influence of Basin-and-Range style extension and of distributed right-lateral shearing of the Pacific-North American plate interactions. The structures hosting the hydrothermal activity at Coso are inherently related to the regional style of deformation.