Strain accumulation in the Southernmost Section of the San Andres fault system in northern Baja California, Mexico

Alejandro Gonzalez-Ortega, Arisai Velazquez-Zaguilan, Jose Javier Gonzàlez-Garcìa, & David T. Sandwell

Published August 15, 2019, SCEC Contribution #9743, 2019 SCEC Annual Meeting Poster #195

We have deployed and measured a very dense GPS array across the Cerro Prieto (CPF) and Imperial (IF) faults, in the southernmost section of the San Andreas Fault System in Mexicali Valley, Baja California, Mexico, to determine the extension of elastic strain buildup and deformation is taking place on the main and secondary set of faults in the area.
GPS monuments (+70) consist of stainless-steel couplers cemented into massive concrete structures and GPS antennas are screwed directly into the couplers for accurate and rapid temporal deployment since 2011 to 2019. GPS position estimates are processed with GAMIT/GLOBK software in ITRF2008 reference frame and site velocities are computed by least squares linear fitting to time variation of coordinates for each station, rotated with respect to Stable North America Reference Frame (SNARF) and projected to main strike slip directions of the faults.
We obtain high velocity gradients of 30-35 mm/yr in 50 km across the CPF and IF, slip rates of 31.6±1.2 mm/yr for IF and 28.4±1.3 mm/yr for CPF using a simple elastic dislocation model which describes the accumulation of elastic strain along a strike‐slip fault. However, slip rates might be influenced by the 2010 Mw7.2 El Mayor-Cucapah postseismic relaxation, including the Indiviso Fault (west and ~parallel to CPF) and a possible Northwest continuation of the CPF, which may accommodate slip rates previously only attributed to the CPF and IF, leading to an improvement in our current understanding of fault strike slip accommodation in northern Baja California, Mexico.

Citation
Gonzalez-Ortega, A., Velazquez-Zaguilan, A., Gonzàlez-Garcìa, J., & Sandwell, D. T. (2019, 08). Strain accumulation in the Southernmost Section of the San Andres fault system in northern Baja California, Mexico. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)