TY - JOUR
T1 - New Kinematic Models for Pacific-North America Motion from 3 Ma to Present, II: Evidence for a “Baja California Shear Zone”
AU - Dixon, Timothy H.
AU - Farina, Farina
AU - DeMets, Charles
AU - Suarez-Vidal, Francisco
AU - Fletcher, John
AU - Marquez-Azua, Bertha
AU - Miller, Meghan
AU - Sanchez, Osvaldo
AU - Umhoefer, Paul
PY - 2000/12/1
Y1 - 2000/12/1
N2 - 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.”
AB - 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.”
UR - https://digitalcommons.usf.edu/geo_facpub/478
UR - https://doi.org/10.1029/2000GL008529
U2 - 10.1029/2000GL008529
DO - 10.1029/2000GL008529
M3 - Article
VL - 27
JO - Geophysical Research Letters
JF - Geophysical Research Letters
ER -