Sequence of cascading earthquakes on the Newport-Inglewood-Rose Canyon Fault zone from paleoseismic observations

Drake M. Singleton, Thomas K. Rockwell, & Jillian M. Maloney

Published August 14, 2018, SCEC Contribution #8488, 2018 SCEC Annual Meeting Poster #219

Approximately 10-20% of the estimated 50 mm/yr plate boundary deformation in southern California is accommodated by the offshore faults that comprise the Inner Continental Borderlands (ICB). The precise distribution of slip and earthquake history in the ICB is poorly constrained due to a combination of observational limitations and a lack of geophysical and geological data integration. The Newport-Inglewood-Rose Canyon fault (NIRC) is the easternmost fault in the ICB and is composed of both onshore and offshore segments, offering the opportunity to resolve the earthquake history for a fault within the ICB. We present the results of two paleoseismic trenches opened in Holocene stratigraphy across the Rose Canyon fault (RCF), the southern onshore section of the NIRC in San Diego, CA. From the stratigraphic record in the trenches, there is evidence for six surface ruptures in the past ~3,300 years. Based on the width and amount of faulting, four of the paleo-earthquakes are interpreted to represent larger-magnitude events (M ~6.5-7). Furthermore, these events correlate well in time with paleo-earthquakes reported at locations farther north along the onshore NIRC, indicating the possible occurrence of either end-to-end ruptures or a sequence of cascading earthquakes. The apparent timing of these earthquakes suggests a late-Holocene recurrence interval of ~700-800 years for the NIRC, several hundred years shorter than previous estimates, and raises important questions regarding the slip rate and slip per event for the southern NIRC. Furthermore, an apparent lack of documented young earthquakes along the northern most section on the NIRC strengthens previous ideas that this section of the fault is likely closer to a failure threshold than the central and southern sections, or that the slip rate has substantially decreased towards the northern terminus of the fault zone.

Key Words
Earthquake Sequence; Paleoseismology; Newport-Inglewood-Rose Canyon Fault Zone

Citation
Singleton, D. M., Rockwell, T. K., & Maloney, J. M. (2018, 08). Sequence of cascading earthquakes on the Newport-Inglewood-Rose Canyon Fault zone from paleoseismic observations. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology