Origin of Regional Uplift across Southern California and Northern Baja California

Grant Kier, Karl J. Mueller, & Thomas K. Rockwell

Submitted 2001, SCEC Contribution #580

Lithospheric flexure produces uplift of the northern Peninsular Range Province in southern California and northern Baja California. Gravity profiles, seismic refraction profiles and tomography constrain numerical models of a free-end elastic plate. Vertical deformation of the elastic plate results from a buoyant force (1.5 x 1012 kg/m in the north model and 2.5 x 1012kg/m in the south) derived from a low density (3.1 g/cm3) mantle anomaly and Vening Meinesz uplift. A flexural model oriented ENE across southern California through San Diego County shows total uplift at the rift shoulder crest of ~1800 m, uplift at the Pacific coast of ~100 m, and a half-wavelength of 175km. A second, flexural model across northern Baja California also oriented ENE shows total uplift at the rift shoulder crest of 3080 m, uplift at the Pacific coast of ~130 m, and a half-wavelength of 177km. Uplift in each numerical model closely matches topography. We argue that the Sierra Juarez and Sierra San Pedro Martir are distinct rift shoulder segments truncated by the Matomí and Sierra La Tinaja accommodation zones. Further, we suggest that flexural uplift across the region may account for ~ 65-83% of total coastal uplift recorded in raised marine terraces adjacent to the northern rift segment and 83-100% of uplift adjacent to the southern rift segment.

Citation
Kier, G., Mueller, K. J., & Rockwell, T. K. (2001). Origin of Regional Uplift across Southern California and Northern Baja California. Tectonics, (submitted).