COMBINED GRAVITY AND SEISMIC INTERPRETATION OF THE PALOS VERDES AND CABRILLO FAULTS

This study presents a joint gravity and seismic interpretation of the Palos Verdes and Cabrillo faults. During the summer of 2013, approximately 125 new gravity measurements were made in the San Pedro and Los Angeles Harbor region. These data show a gravity high near the Cabrillo fault and large approximately 30 mgal decrease northwards toward the Palos Verdes fault. The Palos Verdes fault itself is characterized by an inflection in the gravity data and a relatively flat zone immediately to the north. This shelf in the gravity data is important because the highly productive Wilmington oil field sits in this region and is likely a product of the particular fault geometry in the region. The fault also forms the edge of the larger Los Angeles basin. Our initial interpretation is that down drop of the Catalina schist basement rocks and subsequent basin fill is responsible for the large negative gravity anomaly associated with the Palos Verdes Fault. USGS seismic data collected in the Los Angeles Harbor main ship channel show dipping strata in the region of the large negative gravity decrease. One interpretation is that these are growth strata progressively deposited during movement of the Palos Verdes fault. To better constrain the geometry of the Palos Verdes and Cabrillo faults and additional structures such as folds, gravity models, constrained by existing geologic and seismic data, will be constructed.