INTERACTIONS OF ACTIVE SINISTRAL AND DEXTRAL FAULTS IN THE CENTRAL MOJAVE DESERT, CALIFORNIA

East-striking sinistral faults in the northern Mojave Desert form a domain that extends from the eastern segment of the Garlock fault south to near Ludlow, CA and is surrounded by northwest-striking dextral faults. The sinistral faults have very little resolved sinistral shear stress because maximum stress is nearly perpendicular to the faults, yet several are active (cut Holocene deposits), as are adjacent dextral faults. Puzzles associated with the faults include the behavior of domain boundaries, the magnitude and timing of fault slip and vertical-axis block rotations, and whether new faults initiate as old faults are abandoned. We have conducted detailed mapping, determined ages and remanent magnetizations of Miocene strata, acquired detailed aeromagnetic data, and evaluated LiDAR topographic data to examine these puzzles. Major findings to date include: (1) Apparently complex geometry of the west side of the sinistral fault domain is greatly simplified by the recognition of a new NNW-striking active dextral fault (Paradise fault). (2) The southern three sinistral faults (Cave Mountain, Manix, and Cady faults) are active, whereas the northern faults last ruptured during the late Pleistocene. (3) However, total offsets on the three southern sinistral faults range from 4-6 km to less than 1 km, less offset than those to the north. (4) Also, vertical-axis rotations of these southern blocks are significantly less than the northerly blocks. (5) Sinistral faults are interwoven in time and space with dextral faults along the east side of the sinistral domain. (6) Smaller fault blocks and off-fault strain manifested by folding locally accommodate slip at domain boundaries. These observations indicate that boundaries between dextral and sinistral domains consist of dynamically adjusting small tectonic blocks and that east-striking faults represent a stable, if enigmatic, mode of failure in the Mojave Desert.