Holocene geologic slip rate for the Mission Creek fault at the Three Palms site in the Indio Hills

Juan J. Munoz, Whitney M. Behr, Warren D. Sharp, Rosemarie Fryer, & Peter O. Gold

Published August 14, 2016, SCEC Contribution #6763, 2016 SCEC Annual Meeting Poster #127

Slip on the southern San Andreas fault in the northwestern Coachella Valley in Southern California is partitioned between three strands, the Mission Creek, Garnet Hill, and Banning strands. In the vicinity of the Indio Hills, the NW striking Mission Creek strand extends from the Indio Hills into the San Bernardino Mountains, whereas the Banning and Garnet Hill strands strike WNW and transfer slip into the San Gorgonio Pass region. Together, these three faults accommodate ~20 mm/yr of right-lateral motion. Determining which strand accommodates the majority of fault slip and how slip rates on these strands have varied during the Quaternary is critical to seismic hazard assessment for the southern California region. Here we present a new Holocene geologic slip rate from an alluvial fan offset along the Mission Creek strand at the Three Palms site in the Indio Hills. Field mapping and remote sensing using the B4 LiDAR data indicates that the Three Palms fan is offset ~57 +/- 3 meters. U-series dating on pedogenic carbonate rinds collected at 25-100 cm depth within the fan deposit constrain the minimum depositional age to 3.49 +/- 0.92 ka, yielding a maximum slip rate of 16 +6.1/-3.8 mm/yr. This Holocene maximum slip rate overlaps within errors with a previously published late Pleistocene slip rate of 12-22 mm/yr measured at Biskra Palms, a few kilometers to the south. Cosmogenic 10Be surface exposure samples were also collected from the fan surface to bracket the maximum depositional age. These samples have been processed and are currently awaiting AMS measurement.

Key Words
San Andreas fault, slip rate, cosmogenics, U-series dating, tectonics, Mission Creek fault, northern Coachella Valley

Citation
Munoz, J. J., Behr, W. M., Sharp, W. D., Fryer, R., & Gold, P. O. (2016, 08). Holocene geologic slip rate for the Mission Creek fault at the Three Palms site in the Indio Hills. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Southern San Andreas Fault Evaluation (SoSAFE)