Guadalupe Island as a constrain for earthquake hazard at Californias's shoreline

Jose Javier Gonzàlez-Garcìa, Alejandro Gonzalez-Ortega, John E. Galetzka, Christian Walls, Hebert Martinez-Barcena, & Juan C. Robles

Submitted August 29, 2016, SCEC Contribution #6778, 2016 SCEC Annual Meeting Poster #146

For the purpose of tectonic-earthquake hazard in the Pacific-NorthAmerica western border region, we look for high accuracy of relative plate boundary instead of having global coverage (e.g. GEODVEL, MORVEL56, ITRF2008PPM, GSRM2); by imposing Guadalupe Island GPS velocity to be part of the Pacific Plate motion model. We obtain updated GPS velocity at Guadalupe Island in 3 surveyed campaign sites: GAIR, GUAD and RMGU, and the permanent site GUAX recently upgraded in June 2016. We process the data obtained since 1999 to date using GAMIT/GLOBK and align the results to ITRF2008 using IGS. Our preliminary velocity (mm/yr) for GUAX is 24.9n, -47.2e and -0.21 up.
Mean horizontal velocity for Guadalupe is 25.0n, -47.1e, consistent with our former results and with GUAX.pbo.nam08.pos. Our model for Pacific Plate motion, including our 4 GPS sites at Guadalupe and 23 published velocities (DeMets, et al, 2014) from other Pacific Ocean islands is -62.63n,107.89e and 0.677°/Myr. Residuals (mm/yr) for emblematic sites in the California shoreline are: FARB -1.2n,0.4e; HARV -1.1n,-0.3e; P172 -1.6n,-0.2e and VNDP -2.2,-0.5. Then, there are minor earthquake hazard for offshore faults west of this sites.
Comparison of our GPS velocity at Guadalupe Island with recent global models shows no residual for GSRM2, and only -0.9n, 0.6e for NNRMORVEL56. This indicate that Guadalupe Island belongs to the Pacific Plate for as both geodetic and geologic models between 1mm/yr bounding error.

Key Words
Guadalupe Island, GPS, Pacific Plate

Citation
Gonzàlez-Garcìa, J., Gonzalez-Ortega, A., Galetzka, J. E., Walls, C., Martinez-Barcena, H., & Robles, J. C. (2016, 08). Guadalupe Island as a constrain for earthquake hazard at Californias's shoreline. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Tectonic Geodesy