A Fault-Based Model for Crustal Deformation, Fault Slip Rates, and Off-Fault Strain Rate in California

Yuehua Zeng, & Zheng-Kang Shen

Published 2016, SCEC Contribution #7214

We invert Global Positioning System (GPS) velocity data to estimate fault slip rates in California using a fault-based crustal deformation model with geologic constraints. The model assumes buried elastic islocations across the region using Uniform California Earthquake Rupture Forecast Version 3 (UCERF3) fault geometries. New GPS velocity and geological slip-rate data were ompiled by the UCERF3 deformation working group. The result of least-squares inversion shows that the San Andreas fault slips at 19–22 mm=yr along Santa Cruz to the North Coast, 25–28 mm=yr along the central California creeping segment to the Carrizo Plain, 20–22 mm=yr along the Mojave, and 20–24 mm=yr along the Coachella to the Imperial Valley.Modeled slip rates are 7–16 mm=yr lower than the preferred geologic rates from the central California creeping section to the San Bernardino North section. For the Bartlett Springs section, fault slip rates of 7–9 mm=yr fall within the geologic bounds but are twice the preferred geologic rates. For the central and eastern Garlock, inverted slip rates of 7.5 and 4:9 mm=yr, respectively, match closely with the geologic rates. For the western Garlock, however, our result suggests a low slip rate of 1:7 mm=yr. Along the eastern California shear zone and southern Walker Lane, our model shows a cumulative slip rate of 6:2–6:9 mm=yr across its east–west transects, which is ∼1 mm=yr increase of the geologic estimates. For the off-coast faults of central California, from Hosgri to San Gregorio, fault slips are modeled at 1–5 mm=yr, similar to the lower geologic bounds. For the off-fault deformation, the total moment rate amounts to 0:88 × 1019 N·m=yr, with fast straining regions found around the Mendocino triple junction, Transverse Ranges and Garlock fault zones, Landers and Brawley seismic zones, and farther south. The overall California moment rate is 2:76 × 1019 N·m=yr, which is a 16% increase compared with the UCERF2 model.

Citation
Zeng, Y., & Shen, Z. (2016). A Fault-Based Model for Crustal Deformation, Fault Slip Rates, and Off-Fault Strain Rate in California. Bulletine Seismological Society of America, 106(2). doi: 10.1785/0120140250.

Related Projects & Working Groups
Community Geodetic Model, Tectonic Geodesy