New constraints on relative motion between the Pacific Plate and Baja California microplate (Mexico) from GPS measurements

Abstract

SUMMARY We present a new surface velocity field for Baja California using GPS data to test the rigidity of this microplate, calculate its motion in a global reference frame, determine its relative motion with respect to the North American and the Pacific plates, and compare those results to our estimate for Pacific–North America motion. Determination of Pacific Plate motion is improved by the inclusion of four sites from the South Pacific Sea Level and Climate Monitoring Project. These analyses reveal that Baja California moves as a quasi‐rigid block but at a slower rate in the same direction, as the Pacific Plate relative to North America. This is consistent with seismic activity along the western edge of Baja California (the Baja California shear zone), and may reflect resistance to motion of the eastern edge of the Pacific Plate caused by the ‘big bend’ of the San Andreas fault and the Transverse Ranges in southern California.

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

“…The direction of motion of the Pacific plate and Baja California relative to North America is similar, but Baja California moves at a rate that is ∼ 10% slower than the Pacific plate (Dixon et al, 2000;Plattner et al, 2007). Thus, Baja California behaves as a separate microplate, which is only partially coupled to the Pacific plate (Dixon et al, 2000;Plattner et al, 2007Plattner et al, , 2009). Dixon et al (2000) suggest that the relative movement between the Pacific plate and the Baja California microplate is accommodated by offshore slip along several active fault zones, collectively named the Baja California shear zone.…”

“…Geological observations and GPS measurements show that Baja California behaves as a rigid block Umhoefer and Dorsey, 1997;Plattner et al, 2007). The direction of motion of the Pacific plate and Baja California relative to North America is similar, but Baja California moves at a rate that is ∼ 10% slower than the Pacific plate (Dixon et al, 2000;Plattner et al, 2007).…”

“…These studies attribute the strong deformation of the upper-mantle xenoliths to shearing along either a lithospheric-scale transcurrent shear zone or a subhorizontal shear zone in the shallow mantle, which decouples the deeper mantle from the lower crust of the Baja California microplate. In both cases, deformation in the upper-mantle xenoliths may be associated with the relative motion between the northern Baja California microplate and the Pacific plate (Plattner et al, 2007(Plattner et al, , 2009.…”

“…The San Clemente (SC), San Isidro (SI), San Benito (SB), Tosco-Abreojos (TA), San Lazaro (SL), Santa Margarita (SM), and Todos Santos (TS) faults comprise parts of the Baja California shear zone. Arrows indicate the relative movement of the Pacific plate and the Baja California microplate with that of the North American plate (Plattner et al, 2007). Inset is a tectonic map of the Pacific-North American plate boundary, showing the location of the Baja California shear zone and the San Quintín volcanic field relative to the San Andreas fault (SAF) and the Coyote Lake volcanic field (CL).…”

An Attenuation Study of Body Waves in the South-Central Region of the Gulf of California, Mexico

“…The GoC was created 12 million years ago as a result of continental drift between the Pacific and North American plates (Karig and Jensky, 1972). Tectonically, the Baja California peninsula and the southern GoC are part of the Pacific plate, which is moving northwest relative to the North American plate, which contains the rest of Mexico (DeMets and Dixon, 1999;Plattner et al, 2007;DeMets et al, 2010). The modern-day boundary between these two plates is composed of short, nascent ridge centers connected by transform faults within the GoC (Thatcher and Brune, 1971;Suárez-Vidal et al, 1991;Axen and Fletcher, 1998;Aragón-Arreola and Martin-Barajas, 2007).…”