Shallow fault mapping in the Sacramento-San Joaquin Delta

Shannon A. Klotsko, Jillian M. Maloney, & Janet Watt

Published August 8, 2018, SCEC Contribution #8330, 2018 SCEC Annual Meeting Poster #246

In fall 2017, a chirp and sidescan survey was conducted in the Sacramento-San Joaquin Delta (Delta) to map and characterize shallow fault locations and geometries. The most prominent fault observed in the data is the Kirby Hills Fault, located at the western extent of the Delta. The new chirp coupled with legacy, lower frequency USGS data reveal the fault’s deep structure as well as the shallow deformation. The fault offsets the Delta floor, suggesting relatively recent activity. The Midland Fault is the main fault that traverses the central Delta. Only one crossing of the Midland Fault images near-surface deformation, with acoustic reflectors dipping down into the fault on the west side and flat-lying reflectors on the eastern side. This same stratigraphic pattern is observed in a deep penetration, onshore seismic line from the region. Very slight deformation is also observed along minor faults that were first described from well data in the Rio Vista and River Island gas fields. Well data indicate that there has not been any recent activity on these faults, so the shallow deformation observed may be solely from fluvial processes.

Key Words
Sacramento-San Joaquin Delta, chirp, Sacramento basin, faults, Kirby Hills, Midland

Citation
Klotsko, S. A., Maloney, J. M., & Watt, J. (2018, 08). Shallow fault mapping in the Sacramento-San Joaquin Delta. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology