New Kinematic Models for Pacific-North America Motion from 3 Ma to Present, II: Evidence for a “Baja California Shear Zone”
Digital Object Identifier (DOI)
We use new models for present-day Pacific-North America motion to evaluate the tectonics of offshore regions west of the Californias. Vandenburg in coastal Alta California moves at the Pacific plate velocity within uncertainties (∼1 mm/yr) after correcting for strain accumulation on the San Andreas and San Gregorio-Hosgri faults with a model that includes a viscoelastic lower crust. Modeled and measured velocities at coastal sites in Baja California south of the Agua Blanca fault, a region that most previous models consider Pacific plate, differ by 3–8 mm/yr, with coastal sites moving slower that the Pacific plate. We interpret these discrepancies in terms of strain accumulation on known on-shore faults, combined with right lateral slip at a rate of 3–4 mm/yr on additional faults offshore peninsular Baja California in the Pacific. Offshore seismicity, offset Quaternary features along the west coast of Baja California, and a discrepancy between the magnetically determined spreading rate in the Gulf Rise and the total plate rate from a geological model provide independent evidence for a “Baja California shear zone.”
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Citation / Publisher Attribution
Geophysical Research Letters, v. 27, issue 23, p. 3961-3964
Scholar Commons Citation
Dixon, Timothy H.; Farina, Farina; DeMets, Charles; Suarez-Vidal, Francisco; Fletcher, John; Marquez-Azua, Bertha; Miller, Meghan; Sanchez, Osvaldo; and Umhoefer, Paul, "New Kinematic Models for Pacific-North America Motion from 3 Ma to Present, II: Evidence for a “Baja California Shear Zone”" (2000). School of Geosciences Faculty and Staff Publications. 478.