Undocumented faults revealed in multisensor image analysis, Mojave Desert, California, U.S.A.

Summary

Undocumented late Miocene and younger strike-slip and normal faults that extend up to 25 km in the eastern, and northeastern Mojave Desert block have been detected and mapped using Landsat thematic mapper (TM), SPOT panchromatic, and synthetic-aperture radar (SAR) images. The faults are located in the Bristol Mountains, Cady Mountains, Alvord Mountain, and Granite Mountains (Fort Irwin military reservation) areas. Some faults are perceived on the TM images because of spectral contrasts primarily at infrared wavelengths. Other faults are highlighted on SPOT panchromatic and radar images because of topographic contrasts. Corregistration of enhanced TM/SPOT panchromatic data maximizes both spectral and topographic information in the images. The newly detected faults form part of a complex regional network of right shear in eastern California that connects faults in the southern Death Valley region with the San Andreas fault system. Structural relations along. the faults suggest at least two intervals of movement and a westward migration of the locus of strain in the southern Mojave. In the Bristol Mountains east of Broadwell Lake, the faults are overlain by undisturbed Pleistocene alluvial fan deposits and are probably inactive. In contrast, the area to the west (Cady Mountains) and south contains faults that cut all deposits and is seismically active. Some faults in the Cady Mountains bound blocks that have experienced differing rotational histories since middle Miocene time. Newly identified faults in the northeastern Mojave suggest that right-slip may be more important to the overall deformation than previously reported.