Seismic and aseismic deformation associated with the 1952 Kern County, California, earthquake and relationship to the Quaternary history of the White Wolf Fault

Synthesis of geodetic, geologic, and seismic data from the White Wolf fault, California, indicates that the fault separates an area of late Quaternary and continuing rapid uplift in the Tehachapi Mountains and Transverse Ranges from even more rapid subsidence in the southern San Joaquin Valley. On July 21, 1952, rupture of the White Wolf fault produced the M L = 7.2 Kern County earthquake. We used the aftershock zone to delimit the size of the faulted slip surface and applied constraints imposed by the known 1952–1953 horizontal shear strains to model the measured coseismic vertical displacements, with an elastic dislocation model. A curved fault trace with decreasing fault depth (27 to 10 km from the surface vertically to the base), slip (3 to 1 m), and dip (75° to 20°) from the 1952 epicenter at the southwest end of the fault toward the northeast provides the fit most consistent with the geodetic record, the measured seismic moment, the fault‐plane solution, and the pattern of surface rupture. Two short releveled lines near the 1952 epicenter tilted 4 and 17 μrad down to the north from 5–10 years before the earthquake; the preseismic tilts differ significantly from ten other surveys of these lines. Left‐lateral fault‐crossing shear strain from 0.2–20 years before the quake was two times greater than both preseismic off‐fault strains and the post‐seismic fault‐crossing strains. During the first seven years after the earthquake, aseismic deformation was negligible. From 1959 to 1972 uplift reached 160 mm over an area larger than the aftershock zone, rising first in the epicentral region and then at the northeast end of the fault. This was unaccompanied by any surface fault slip. Reconstruction of the vertical separation on the White Wolf fault from late Quaternary and late Miocene stratigraphic marker beds shows that the rate of reverse fault slip increased forty‐fold, from 0.1–0.2 mm/yr to 3–9 mm/yr, between the past 10–15 m.y. and the most recent 0.6–1.2 m.y. We estimate a 170‐ to 450‐yr average recurrence interval for earthquakes on the White Wolf fault with slip equivalent to that in 1952. The 1952 earthquake appears to be characteristic of the Quaternary record of fault displacement in the increase in White Wolf slip toward the San Andreas fault, the ratio of reverse to lateral slip (1.3:1), and the ratio of vertical fault slip to emergence of the hanging wall block (3:1). The >8500‐m‐deep sedimentary basin on the down‐thrown block cannot be explained by repeated slip of the White Wolf fault in an elastic medium.