AN UPDATED EVALUATION OF THE ROSE CANYON FAULT ZONE, SAN DIEGO, CALIFORNIA

The Rose Canyon Fault Zone (RCFZ) extends from La Jolla to San Diego Bay and is the southern, onshore section of the 170-km long Newport-Inglewood/Rose Canyon fault zone. The RCFZ is approximately 20 km in length and is a predominantly right-lateral strike-slip system with local reverse-oblique movement resulting in uplift of Mt Soledad, and right-normal, oblique extensional faulting responsible for the formation of San Diego Bay. Previous studies by the California Geological Survey (CGS) resulted in establishment of Alquist-Priolo Earthquake Fault Zones (APEFZs) for a portion of the fault zone from La Jolla to De Anza Cove, the Spanish Bight, Coronado, and Silver Strand faults in San Diego Bay, and the downtown graben and San Diego fault in downtown San Diego. However, evidence was insufficient to support zoning of central portions of the fault zone through Old Town and east of Mission Bay. We recently re-evaluated the RCFZ within the La Jolla and Point Loma 7.5’ quadrangles for the APEFZ program. Recent subsurface geologic investigations at the San Diego International Airport confirmed the northern projection of the Spanish Bight fault and identified a previously unmapped Holocene-active fault informally named the “East Bay” fault. Paleoseismic studies at the Presidio Hills Golf Course in Old Town San Diego provide evidence for multiple late-Holocene surface rupturing events on the RCFZ. Fault investigations downtown confirm the Holocene-active Coronado fault comes onshore at Seaport Village and suggest continuity with the “Pacific Highway” fault, previously identified as a north-south trending pre-Holocene structure located east of Pacific Highway. Additionally, recent mapping and interpretation of fault-related geomorphic features for the Mid-Coast Corridor Transit Project provide evidence for Holocene fault activity east of Mission Bay and suggest Holocene activity and continuity of the entire RCFZ from La Jolla to San Diego Bay. Our current evaluation considers this new data for development of updated APEFZ Special Studies Zones maps.