Active Tectonics of the Northeastern Mojave Desert, California.

This study has led to an improved understanding of the active tectonics and seismic hazards of the northeastern Mojave Desert region and has provided a means with which to assess regional strain models proposed by previous workers. Primary data sets include published and unpublished geologic maps, Landsat Thematic Mapper multi-spectral imagery, SPOT panchromatic imagery as well as hand-held ground and aerial photographs (panchromatic, color and color-infrared), color video, digital topography, gravity, seismicity and paleomagnetic data. Prior to analysis, data sets were organized into a geographic information system implemented on a UNIX workstation. This allowed for the simultaneous visualization of combinations of data sets in order to gain new perspectives on spatial and temporal relationships. Most faults of the northeastern Mojave Desert region have moved in late Quaternary time with many currently active and seismogenic. The most prominent zone of seismicity is along the Goldstone Lake fault zone. It is proposed that the net right slip across the Goldstone Lake fault zone is $\sim$10 km. This amount of displacement represents $\sim$18% of the total right-shear, $\sim$57 km, likely to have occurred across the northeastern Mojave Desert since $\sim$6-10 Ma. Paleomagnetism studies confirm that there has been little to no regional vertical-axis rotation of the Goldstone Lake region since $\sim$22 Ma. This result constrains the northern limit of early Miocene, regional crustal rotations which formed as a consequence of right shear along the Trans Mojave-Sierran shear zone. Furthermore, geometric/kinematic models of the late Cenozoic tectonic evolution of the northeastern Mojave Desert which require regional vertical-axis rotations of this region are refuted by this result. The Goldstone Lake fault zone is likely more significant than previously recognized; the location, orientation, length and seismicity of the Goldstone Lake fault zone give cause to conclude that it may be capable of producing earthquakes similar in magnitude to that of the Landers earthquake (M = 7.3, June 28, 1992)