Birth of a fault: Connecting the Kern County and Walker Pass, California, earthquakes

A band of seismicity transects the southern Sierra Nevada range between the northeastern end of the site of the 1952 M W (moment magnitude) 7.3 Kern County earthquake and the site of the 1946 M W 6.1 Walker Pass earthquake. Relocated earthquakes in this band, which lacks a surface expression, better delineate the northeast-trending seismic lineament and resolve complex structure near the Walker Pass mainshock. Left-lateral earthquake focal planes are rotated counterclockwise from the strike of the seismic lineament, consistent with slip on shear fractures such as those observed in the early stages of fault development in laboratory experiments. We interpret this seismic lineament as a previously unrecognized, incipient, currently blind, strikeslip fault, a unique example of a newly forming structure.

[1]  J. Stock,et al.  Pacific-North America Plate Tectonics of the Neogene Southwestern United States: An Update , 1998 .

[2]  William R. Lettis,et al.  Empirical observations regarding reverse earthquakes, blind thrust faults, and quaternary deformation: Are blind thrust faults truly blind? , 1997, Bulletin of the Seismological Society of America.

[3]  G. Schreurs.  Experiments on strike-slip faulting and block rotation , 1994 .

[4]  A. Michael,et al.  Three‐dimensional velocity structure, seismicity, and fault structure in the Parkfield Region, central California , 1993 .

[5]  Edi Kissling,et al.  Geotomography with local earthquake data , 1988 .

[6]  L. Jones,et al.  Evidence of basin-and-range extensional tectonics in the Sierra Nevada: The Durrwood Meadows swarm, Tulare county, California (1983-1984) , 1986 .

[7]  John M. Logan,et al.  Experimental folding and faulting of rocks under confining pressure Part IX. Wrench faults in limestone layers , 1981 .

[8]  S. K. Chakrabarty,et al.  The Walker Pass earthquakes and structure of the Southern Sierra Nevada , 1949 .

[9]  T. Lay,et al.  Analysis of the 1986 Mt. Lewis, California, earthquake: preshock sequence-mainshock-aftershock sequence , 1993 .

[10]  D. C. Ross.  The metamorphic and plutonic rocks of the southernmost Sierra Nevada, California, and their tectonic framework , 1989 .

[11]  F. W. Klein,et al.  User's guide to HYPOINVERSE, a program for VAX computers to solve for earthquake locations and magnitudes , 1989 .

[12]  D. C. Ross.  Basement-rock correlations across the White Wolf-Breckenridge-southern Kern Canyon fault zone, southern Sierra Nevada, California , 1986 .

[13]  David Oppenheimer,et al.  FPFIT, FPPLOT and FPPAGE; Fortran computer programs for calculating and displaying earthquake fault-plane solutions , 1985 .