Plate Boundary Observatory Southwest Region Network Operations, Expansion and Communications Hardening

Abstract:

The Southwest Region of the Plate Boundary Observatory manages 480 continuously operating GPS stations located principally along the transform system of the San Andreas fault, Eastern California Shear Zone and the northern Baja peninsula. In the past year, network uptime averaged 98% with greater than 99% data acquisition.

In an effort to modernize the network, we have started to replace Trimble NETRS receivers with GNSS capable NETR9 receivers. Currently, we have 431 NetRS receivers deployed in the region, and 48 NetR9 receivers. In addition, 82 stations (17%) stream 1 Hz data over the VRS3Net typically with <0.5 second latency and an average completeness of >92%. Based on their typical data download rates, approximately 252 (53%) of all stations are capable of streaming 1 Hz, but have not yet been added to the real time network because of lack of resources. In the immediate aftermath of the M8.2 Chile earthquake in April 2014, high rate data downloads from the entire SW network had a success rate of 95% and 71% for 1 Hz and 5 Hz data downloads respectively.

We have continued to upgrade critical radio networks, including the San Francisco Bay Area, Anza Borrego, and Santa Barbara networks. These efforts are ongoing, but they have already significantly improved data download rates and dependability. We are also converting cell modem to radio communications whenever possible for increased reliability and cost savings.

In December 2013 the 13-station Edison network expansion was completed through cost recovery contracts. These stations span coastal southern California in Orange, San Diego and Los Angeles counties including a hybrid site on the Elly oil platform. The primary purpose of the stations is to aid in the seismic source characterization of the San Onofre Nuclear Generating Station and assess the strain field associated with the Oceanside Blind Thrust and Newport Inglewood fault. The new stations fill a gap between SCIGN and PBO. Three sites have WXT520 Vaisala metpacks and twelve stations stream 1Hz data via VRS3Net.

UNAVCO and SCRIPPS are working in collaboration to augment a subset of stations with low-cost strong-motion sensors along the San Andreas and San Jacinto faults. To date twelve PBO stations have been upgraded with MEMS accelerometer packages.