Seismogeodetic Observations of the June 10, 2016 M5.2 Borrego Springs Earthquake

Dara E. Goldberg, Jessie K. Saunders, Jennifer S. Haase, & Yehuda Bock

Submitted August 15, 2016, SCEC Contribution #7024, 2016 SCEC Annual Meeting Poster #256

Seismogeodesy is the optimal combination of high rate GPS observations and strong motion accelerations in a Kalman filter to produce broadband velocity and displacement waveforms, including accurate measure of the static offset. This approach requires collocated GPS and accelerometer instrumentation. Our group developed a low cost geodetic module and MEMS accelerometer package (SIO GAP) that is installed on the vertical leg of existing cGPS stations and whose data is communicated along with the GPS data in real time. So far, SIO GAPs have been installed at 17 PBO/SCIGN stations spanning the San Andreas, San Jacinto, and Elsinore Faults and at 10 PBO stations in the San Francisco Bay Area.

On June 10, 2016 a M5.2 earthquake occurred in Borrego Springs, California, near the San Jacinto Fault. The earthquake was widely felt in southern California, and was observed on seismogeodetic instrumentation located 17 km to 100 km from the source. We present a retrospective analysis of the data and early warning products available from the collocated sites.

We compare seismogeodetic combinations using observatory-grade accelerometers to those using the SIO GAPs to demonstrate the capabilities of these low-cost instruments in the field. While the collocated PiƱon Flat station PIN2 does not measure the anomalously high PGA observed at nearby observatory-grade strong motion station PFO, the seismogeodetic waveforms exhibit similar characteristics, with particularly good agreement in the velocities. We show the utility of the seismogeodetic velocities for detection of first seismic arrivals as well as the results of our rapid event location and shaking onset prediction as part of our prototype seismogeodetic early warning system. From the location estimate, we estimate the moment magnitude using a simple scaling relation from peak ground displacement measured from the seismogeodetic displacement.

This event was also observed on seismogeodetic instrumentation used for structural monitoring at a parking garage at the Automatous University of Baja California Faculty of Medicine in Mexicali. The observations show the building response, and demonstrate the feasibility of structural monitoring using seismogeodesy. No discernable displacement was measured at 126 km epicentral distance, however the MEMS accelerometers were available to provide an estimate of building response with rooftop amplification of 1.5 times in the east component and 2.3 times in the north component.

Key Words
seismogeodesy, early warning

Goldberg, D. E., Saunders, J. K., Haase, J. S., & Bock, Y. (2016, 08). Seismogeodetic Observations of the June 10, 2016 M5.2 Borrego Springs Earthquake. Poster Presentation at 2016 SCEC Annual Meeting.

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