ABSTRACT: Spaceborne Multispectral Images Reveal Undocumented Late Cenozoic Faults, Mojave Desert, California

John P. Ford, R. K. Dokka, R. E. Crippen, R. G. Blom

Undocumented late Miocene and younger strike-slip and normal faults that extend up to 25 km in the eastern and central Mojave Desert Block have been detected and mapped in LANDSAT thematic mapper images. The faults are located in the Bristol Mountains, Cady Mountains, and Alvord Mountain areas. Additional strike-slip faults detected in the adjacent Fort Irwin Military Reservation have yet to be verified in the field. The images were processed to enhance the spectral responses without suppressing topography. The faults are detected on the images because of spectral contrasts mostly at wavelengths longer than the visible. The newly detected faults form part of a complex regional network of right shear that connects faults in the southern Death Valley region with the San And eas Fault System. Some of the newly identified faults bound blocks that have experienced different Neogene rotational histories. These faults have likely served to accommodate those motions. Structural relations along the faults suggest at least two intervals of movement. In the Bristol Mountains, east of Broadwell Lake, the faults are overlain by unconsolidated alluvial fan debris (late Quaternary?) and are probably inactive. In the Cady Mountains to the west and south, the faults cut all deposits and are currently active. The discovery of these undocumented faults indicates that existing knowledge of fault distribution in the area is incomplete and not fully representative. This has important implications for seismic risk assessment and for determining the suitability of the desert for increased use by man.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990