On Easter Sunday, 4 April 2010, the Mw 7.2 El Major-Cucapah earthquake occurred with rupture initiating in Baja California at the southern end of the Cucapah mountains, propagating to the northwest and terminating where the aftershocks concentrated just north of the California border. Since the Mw 7.2 El Major-Cucapah earthquake there has been a migration of seismicity to the north that has included the recent 7 July 2010, Mw 5.4 Collins Valley earthquake. This RAPID award will accelerate the instrument deployment for the existing NSF funded project (EAR-0908903) entitled: Collaborative Research: Structural Architecture and Evolutionary Plate-Boundary Processes along the San Jacinto Fault Zone. This is a joint project between USC, UCSD, San Diego State University, and UNAVCO. This RAPID project will use resources of UNAVCO to provide the most cost effective method for installation of new shallow borehole sensors. The funds are solely for the shallow borehole drilling, since USC is providing the borehole sensors and UCSD is providing the data acquisition system. The RAPID funding will allow for 7 installations.
On Easter Sunday, 4 April 2010, the Mw 7.2 El Major-Cucapah earthquake occurred with rupture initiating in Baja California at the southern end of the Cucapah mountains, propagating to the northwest and terminating where the aftershocks concentrated just north of the California border. Immediately following the Mw 7.2 El Major-Cucapah earthquake there was a migration of seismicity to the north that has included the 7 July 2010, Mw 5.4 Collins Valley earthquake. This is the third M 5+ earthquake along the San Jacinto Fault Zone between the towns of Anza and Borrego Springs since the year 2000. Immediately after the Mw 7.2 El Major-Cucapah earthquake Professor Yehuda Ben-Zion of USC and Dr. Frank Vernon of UCSD looked at the current digital real-time station coverage along the San Jacinto fault and realized there are significant ways to improve the seismic coverage from the Anza Valley down to Ocotillo Wells. Their primary concern in April was that earthquake activity along the San Jacinto Fault would increase and there would be an opportunity to record unique a new scientific dataset, particularly for making on-scale measurements near seismic sources on the San Jacinto Fault. In response to the immediate evolving seismological situation, USC used $66k of internal funds to purchase 11 Kinemetrics SBEPI (Shallow Borehole EpiSensor) Downhole Force Balance Accelerometers. In parallel, UCSD provided 11 dataloggers with matched radios that connect directly into the ANZA seismic network at Toro Peak. NSF RAPID funds were used on this project to support the installation of the equipment in shallow boreholes at critical locations where seismic monitoring did not exist. Four of the sites were collocated with PBO GPS sites to allow integrated GPS-Strong Motion recordings of earthquakes. The remaining sites were deployed near to the surface trace of the San Jacinto Fault to observer near fault behavior of seismic wave and rupture propagation. Data collected through this system are forwarded to the CISN in real-time and to the IRIS DMC for distribution to the scientific community.
