In the second year (10/1/2000-9/30/2001) of ANSS funding the California Integrated Seismic Network (CISN) installed 30 digital seismic stations in the San Francisco Bay region (Figure 1 pdf version or gif image ). As in FY2000, the sites were chosen to address two critical seismic-monitoring needs in the region - construction of real-time ShakeMaps and monitoring of strong shaking in urban areas. To improve the ability of the CISN to create ShakeMaps, the USGS Northern California Seismic Network (NCSN) replaced obsolete analog seismic equipment at 10 existing regional network sites throughout the region with data loggers digitizing output from a tri-axial accelerometer (for strong motion) and a vertical seismometer (for monitoring microearthquakes. The remaining 20 sites were newly installed by the USGS National Strong Motion Program (NSMP) in fire stations, schools, and other facilities located in metropolitan regions of the Bay Area where there were few other strong motion stations. The inventory, locations, and status of all stations installed under ANSS funding are provided in Table 1.
The equipment was installed by the end of the fiscal year at all 30 sites and configured to record on-site if strong shaking occurred. The NCSN was able to establish continuous data telemetry to 8 sites via direct radio and microwave telemetry; the remaining two sites await commercial telephone hookups. We established telemetry to one of the NSMP stations installed at a school, but the others await installation of Frame Relay and DSL service by Pacific Bell. However, in FY2001 we established telemetry to 18 of the 20 NSMP sites installed in FY2000.
In FY2001 the CISN obtained funds to instrument 2 structures in the San Francisco Bay area, the City of Berkeley Civic Center in Berkeley and the Channing House in Palo Alto. Both structures were instrumented by 9/30/2001. These buildings were recommended by different sources including the Architect/Engineering companies and personnel of USGS. Both buildings happen to be retrofit cases by base isolation. The inventory of instrumented base-isolated buildings is very few. In many cases of an urban environment, application of base-isolation to existing buildings is becoming a preferred method for retrofitting. Therefore, the basic primary purpose for instrumenting these buildings was to assess the effectiveness of the base-isolators as the vehicle to retrofit older, sub-code designs.
The Berkeley City Hall building is 6 stories including a lower level basement. The original building is a non-ductile concrete framed building with few shear walls. To protect its historic appearance, base isolation was the only way to retrofit the structure. The retrofit system includes addition of reinforced concrete shear walls above the isolators. There are 74 base-isolators under the retrofitted building, and their anticipated maximum displacement is 27 inches. The building is approximately 1.5 km from the Hayward Fault and may experience large pulses and attendant displacements. Instrumental recordings from the 24 accelerometers installed in this structure will enables the City of Berkeley as well as the scientific and engineering community learn about its performance during the expected earthquakes. In particular, recordings could document (a) the energy dissipation (damping) capabilities of the isolators, (b) the transmission of energy from the foundation to the superstructure, (c) the displacement response of the isolators, (d) behavior of new shear-walls, and (e) the overall integrity of the structure during strong-shaking.
Channing House is a senior citizen apartment building in Palo Alto. The building was completed in 1966 and was originally a non-ductile reinforced concrete framed system with shear walls at stair towers at both ends of the building and center core elevator shaft shear wall. The building has 10 stories, a penthouse, and a basement. The building has 2 wings that meet in a wide "V", and there are no seismic joints between the two wings. The building was retrofitted with a total of 120 base-isolators with a maximum displacement of 17 inches. There is a 17 inch moat to accommodate this displacement. The 12 accelerometers installed in this building will provide data to assess effectiveness of the isolators, translational and torsional motions of the isolators, rocking of the building superstructure above the isolators, translational and torsional motions of the building superstructure and diaphragm effects. They will also provide assessment of the directionality effects of incoming ground motions on the isolators and wings of the building.
The CISN devoted considerable effort to organizational activities in FY2001. The Steering Committee has representation from the 5 institutions primarily responsible for monitoring earthquake activity in California (California Division of Mines and Geology, California Institute of Technology, USGS-Menlo Park, USGS-Pasadena, and the University of California Berkeley), as well as the California Governor's Office of Emergency Services (OES). The CISN convened its first meeting of the Advisory Committee at which time we reviewed the status of funding for networks in the state, organizational issues, and oversight of state and federal funding. A subgroup of the steering committee has written a 5-year Strategic Plan that is in review by the Advisory Committee.
The CISN was successful in obtaining $3.9M in funding from the State of California for state fiscal year 2002. Funding will tentatively begin in November 2001. The details of how these funds are to be spent are described in an Implementation Plan under review by the state. However, in general terms the money will be used to support continued operation of the TriNet system by Caltech and CDMG, the installation of new strong-motion stations in urban areas of Northern California by CDMG, and the installation of broadband instruments in Northern California by UC Berkeley. Funding will also go towards developing statewide, robust operation of the CISN. The CISN will begin efforts to standardize algorithms in southern and northern California so that the real-time software produces the same answer. Funds will also be used to improve the reliability and means of delivering information to OES and the development of redundant and dedicated telemetry links for waveform and parametric exchange between regional centers and OES. The TriNet project in southern California also received funding through ANSS in FY2001 to support on-going operational activities during the period between the end of the FEMA TriNet grant and the beginning of the state of California funding.
With the installation of these 30 stations, the 40 stations in FY2000 of ANSS, and the integration of strong motion information in near real-time from other CISN participating institutions at UC Berkeley, California Division of Mines and Geology, and the Pacific Gas & Electric, there are now over 200 seismic stations in the San Francisco Bay region that are generating data for the creation of a ShakeMap (Figure 1). Even better coverage is available in southern California as a result of the TriNet effort. The CISN has fully implemented automatic generation of ShakeMap, Community Internet Intensity maps, and Recenteqs maps statewide. We provide on the Recenteqs pages automated first-motion mechanisms for most quakes above M2.5 and images of earthquake seismograms. In northern California UCB provides automated regional moment tensors for quakes above M3.5. The ShakeMap project in Pasadena is working closely with the California OES to transmit ShakeMap "shape files" to the agency so that they can incorporate the map into their GIS system.
The CISN has seismologists on standby duty 7X24 who respond to any quake statewide above M3.5 and in urban areas for smaller quakes that are likely to be felt. The response process updates the Recenteqs web page to indicate the information has been reviewed, initiates distribution of this reviewed information through the California OES Emergency Distribution of Information System and QDDS. CISN scientists participate in conference calls with the OES and state officials to provide guidance on the implications of on-going earthquake sequences.