The first site (SAOB) was installed in July 1997 near the San Andreas Geophysical Observatory near Hollister, monitoring the south San Francisco Bay area near the intersection of the San Andreas and Calaveras faults. At SAOB, due to a lack of exposed rock outcrop, a 20 cm diameter hole was drilled five meters deep. Vertical steel reinforcing bars run from the bottom of the hole into the exposed pillar which serves as the antenna mount. The vertical hole was filled with concrete and extended monolithically to include the exposed antenna mount portion.
The second site (MUSB) was installed in November 1997 on Musick Mountain, in the Sierra Nevada range southwest of Mammoth. This site, combined with CMBB, ORVB, and QUIN, provides valuable constraints on the tectonic stability of the Sierra Nevada range, and its relative motion with respect to the Great Valley (these two provinces are often assumed to form a rigid block), and to the central Coast Ranges. MUSB uses a one-meter-high, reinforced-concrete monument attached to exposed granite outcropping near the summit of Musick Mountain. Power and telemetry to this site are supplied by Southern California Edison from their colocated microwave facility. The data is first telemetered via radio modems to the microwave facility, and then via microwave to the next microwave facility where it joins the data stream from the KCC broadband station, which is located 20 km north of MUSB. UC Santa Cruz will provide an Ashtech Z-12 receiver to replace the existing BSL receiver during 1998-99.
The third site (DIAB) was installed in May 1998 in the Mount Diablo State Park. Mount Diablo is one of the most prominent peaks in the east Bay area. Located near the northern Calaveras, Concord, and Livermore faults, this site fills in an important gap in the Farallon-Sierra Nevada profiles, currently making it the most stable BARD station closest to the west side of the Great Valley. The DIAB site is close to a public road near the summit, so a short, half-meter, reinforced-concrete monument was attached to an exposed rock outcropping at this site to limit public visibility. Municipal utilities pass near the site and supply power and frame-relay telemetry.
Laboratory personnel also installed a reinforced concrete monument at the Site 300 explosion testing facility (S300) of the Lawrence Livermore National Laboratory in July 1998. During 1997-98 BSL staff worked closely with LLNL and Trimble representatives to design a multi-purpose system that will primarily be operated by LLNL with a continuous telemetry feed to the BSL. This system will provide real-time kinematic mode surveying capability for precise (cm-level) mapping of archealogical sites and other features at Site 300, publicly available differential corrections for real-time meter-level navigation and position capability in the general vicinity of the site, and real-time telemetry of the raw data stream for the fault monitoring activies at the BSL. The site was chosen for its good site sky visibility, for its availability of rock outcrop enhancing monument stability, and for its proximity to the Great Valley. Because it is located at one of the easternmost sites in the Diablo Range, it will provide valuable constraints on the total deformation accommodated between the Sierra Nevada range and the San Andreas fault system. S300 will become operational in October 1998.
Two more sites were installed in July and August 1998 in the Point Reyes National Park (PTRB) and on Monument Peak (MONB) in the Mission Hills of the east San Francisco Bay area. PTRB, located near the historic Point Reyes lighthouse at the westernmost point of land in the north Bay midway between the San Andreas fault and the Farallon Islands, will provide valuable constraints on deformation west of the San Andreas fault. MONB is located in a tectonically complicated region near the intersection of the Calaveras and southern Hayward faults, where the seismicity appears to step over along the Mission fault.
Installations are also currently being permitted and prepared at several other sites, including Barnabe Peak (BARB), just east of the San Andreas fault in the north Bay area and Potrero Hills (POTB) in the north Bay near the Great Valley. In addition, the BSL will assume operational responsibilities for the LUTZ and SODA sites in the south Bay after replacing the the semi-permanent Trimble receivers currently operated by UC Davis with recently purchased BSL Ashtech receivers, which will be permanently installed, and upgrading to continuous telemetry.
During 1997-98, the USGS installed a receiver near Mammoth (JNPR), so that 4 receivers are now monitoring the volcanic unrest at the Long Valley caldera. In 1998-99, the USGS plans to install four receivers in the Parkfield area to supplement the PKD1 and CARR receivers that are currently monitoring this segment of the San Andreas fault that is expected to rupture in a M6 earthquake in the near future. Also during 1998-99, UC Davis plans to improve the telemetry of the UCD1 receiver located on their campus, and UC Santa Cruz is is preparing to install a semi-permanent receiver on the roof of one of their campus buildings.