Quaternary faulting history along the Deep Springs fault, California

New geologic mapping, structural studies, geochronology, and diffusion eros ion modeling along the Deep Springs fault, California, shed light on its Qu aternary faulting history. The Deep Springs fault, a 26-km-long, predominan tly north-northeast-striking, west-northwest-dipping normal fault bounding the eastern side of Deep Springs Valley, cuts Jurassic batholithic rocks no nconformably overlain by middle Miocene to Pleistocene stream gravels, coar se-grained sand, tuffaceous sand, unwelded to partially welded tuff, and Bi shop ash, as well as Quaternary coarse- to fine-grained alluvial fan deposi ts. The Ar-40/Ar-39 geochronology yields ages of 3.09 +/- 0.08 Ma for the u nwelded tuff and 753 +/- 4 ka for the Bishop ash, Holocene debris Rows, a l andslide, and recent alluvium bury the youngest fault scarp, The Deep Sprin gs fault is characterized by multiple fault planes and fault scarps that be come progressively younger toward the basin. The dip of the fault plane var ies from 20 degrees to 87 degrees and fault-plane and striation measurement s indicate an average orientation of N23E, 47NW, and N77E, 49SW, respective ly. The offset of Bishop ash and underlying tuff across the Deep Springs fa ult indicates horizontal extension and vertical slip rates of similar to0.7 and similar to0.9 mm/yr, respectively, since the eruption of the Bishop Tu ff, and similar to0.2 and similar to0.2 mm/yr, respectively, since the erup tion of the unwelded tuff. If the vertical slip rate since the eruption of the Bishop Tuff has remained constant through time, then slip along the Dee p Springs fault be-gan ca. 1.7 Ma, Younger fault scarps to the west of the bedrock fault cut Quaternary deposits; scarp offset ranges from 0.8 to 17.5 m, and scarp slope angle ranges from 8 degrees to 37 degrees, Topographic profiling of the smallest, least eroded fault scarps, with an average surfa ce offset of 2.7 m, indicates that these scarps developed as the result of a single earthquake and ruptured an similar to 20-km-long segment of the fa ult. Radiocarbon analyses on detrital charcoal, located in the footwall blo ck of one of these scarps, yield an age of 1.960 +/- 0.055 ka, Diffusion er osion modeling of these fault scarps yields an elapsed time of 1.7 +/- 0.5 k.y. since these fault scarps formed. Making reasonable assumptions about t he depth of this earthquake and shear modulus, we estimate a moment magnitu de, M-w approximate to 7.0, for this earthquake. The Deep Springs fault is one of several displacement-transfer normal faults that define a zone of di stributed deformation between subparallel right-lateral strike-slip faults east of the Sierra Nevada that make up the northern part of the Eastern Cal ifornia Shear Zone. The young age and recent earthquake activity along the Deep Springs fault are consistent with a model proposed for the kinematic e volution of this part of the Eastern California Shear Zone.