New kinematic models for Pacific-North America motion from 3 MA to present, II: Evidence for a "Baja California shear zone"

Timothy Dixon, Fred Farina, Charles DeMets, Francisco Suarez-Vidal, John Fletcher, Bertha Marquez-Azua, Meghan Miller, Osvaldo Sanchez, Paul Umhoefer

Research output: Contribution to journalArticlepeer-review

66 Scopus citations

Abstract

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".

Original languageEnglish (US)
Pages (from-to)3961-3964
Number of pages4
JournalGeophysical Research Letters
Volume27
Issue number23
DOIs
StatePublished - 2000

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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