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

Abstract

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 Ms=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 of 0.62±0.16 μstrain/yr across the White Wolf fault. The maximum shear strain rate decreased with distance toward the Garlock fault to 0.09±0.08 μstrain/yr. In the decade following the earthquake (1952–1963), the near fault was high (0.85±0.23μstrain/yr), and decreased to 0.23±0.13 μstrain/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 dropped to 0.19±0.07 μstrain/yr. The azimuths of the maximum principal strain rates (ϕ) for the 1963–1993 epoch rotate from a fault normal orientation (−57°±15°) across the White Wolf fault to 11°±3°E across the Garlock fault.