UC Santa Barbara

Our understanding of earthquakes that occurred prior to the establishment of the World-Wide Standardized Seismographic Network (WWSSN) is generally limited by the availability of high-quality geophysical observations. As a result, significant variability exists among source studies for important seismic events such as the historic 1952 Kern County, California earthquake. Here, combining reported geodetic observations with a collection of previously unused, local seismic recordings, we conduct a series of inversions to constrain a slip model for the main rupture. Our results suggest that it initiates on a low-angle fault plane with dominant strike-slip motion (strike=49±3°; dip=35±1°; and rake=11±5°) then triggers an abnormally energetic rupture on a high-angle fault plane (strike = 51°, dip = 75°), 2 s later. This energetic rupture, contained within a 9×6 km patch near the hypocenter, accumulates 6–7 m of slip and has a high average static stress-drop (larger than 50 MPa). P-waves excited by this powerful sub-event saturates seismic recordings as far as Berkeley (approximately 430 km away). The total rupture has a duration 23–26 s and a cumulative moment of 7.61×10^{19} Nm, or Mw 7.18. The majority of moment release occurs within a 36 km section in the southwest portion of White Wolf fault (assumed to be 60 km long). The weighted, average rake-angle over the southwest segment of the fault is 47–57°, falling between previous results based on individual seismic or geodetic data sets. Investigation of the regional velocity structure reveals high P-wave velocities near the southwest portion of the White Wolf fault, adjacent to the presumed hypocenter.