Geodetic measurements of horizontal strain near the White Wolf fault, Kern County, California, 1926-1993

The White Wolf fault, located north of the Big Bend segment of the San Andreas fault, is the NE-SW trending, left lateral-oblique reverse fault responsible for the M(S)=7.8 1952 Kern County earthquake. We combined Global Positioning System (GPS) measurements with historical triangulation and trilateration data to determine changes in the strain rate over 7 decades (1926-1993). We reanalyzed the historical geodetic data and calculated an elevated preseismic (1926-1952) maximum shear strain rate (gamma over dot) of 0.62 +/- 0.16 mu strain/yr across the White Wolf fault. The maximum shear strain rate decreased with distance toward the Garlock fault to 0.09 +/- 0.08 mu strain/yr. In the decade following the earthquake (1952-1963), the near fault gamma over dot was high (0.85 +/-0.23 mu strain/yr), and decreased to 0.23+/-0.13 mu strain/yr across the Garlock fault. In 1993, we resurveyed many of the same monuments with GPS receivers to estimate fault-crossing and off-fault strain rates for the preceding 30 years. Across the White Wolf fault, the maximum shear strain rate (gamma over dot) dropped to 0.19+/-0.07 mu strain/yr. The azimuths of the maximum principal strain rates (phi) for the 1963-1993 epoch rotate from a fault normal orientation (-57 degrees+/-15 degrees) across the White Wolf fault to 11 degrees+/-3 degrees E across the Garlock fault.