California Division of Water Resources Seismic Network
The Earthquake Engineering section of the California Department of Water Resources (DWR) operates a seismic network for monitoring DWR critical facilities. Data from some of these sites is shared with the USGS Menlo Park and is integrated with other data of the Northern California Seismic System (NCSS). The earthquake epicenters and magnitudes are reported to the DWR Project Operations Center, USBR, Department of Transportation (Caltrans), Division of Safety of Dams, US Corps of Engineers, and PG&E. The magnitudes and epicenters are used to determine the geographical area of the State Water Project requiring inspections after an earthquake. Facilities such as dams, pumping and power plants, switchyards, oil and gas pipelines, pipeline crossings, aqueducts, canal and pipeline, tunnels, intake structures, check structures, and office and maintenance buildings all are inspected based on this data. The uses of the strong motion data are for structural response studies following an earthquake, seismic stability evaluation of Sacramento Delta levees, and dynamic structural analysis of structures on DWR facilities.
The DWR owns and operates 22 free-field seismographic sites throughout California, having 54 weak-motion (seismometer) channels and 48 strong-motion channels, for a total of 102 channels. The real-time data from these sites is transmitted to Sacramento via LAN/WAN, Vsat, fiber optic, leased telephone lines, microwave, and/or radio. The DWR has been actively upgrading short-period, vertical, analog instrumentation. Sixteen (16) of the 22 sites now consist of a 6-channel digital datalogger with 3 SS-1 Rangers and a tri-axial accelerometer (Episensor).
In addition to the weak-motion seismometer sites, DWR operates numerous tri-axial strong-motion accelerometers on structures, including dams, pumping/power plants, aqueduct check structures, siphons, outlet towers, and a few free-field sites. Dams typically have strong-motion sensors placed at the Crest, Toe, Abutments and Downstream. For example, Oroville Dam has eight 3-channel accelerometers, Sisk Dam has 6, and Perris Dam has 5, with a few more sensors planned to be installed in the Perris Outlet Tower. Power/pumping plants typically have sensors at ground level and in the lower gallery. At present, 361 channels of structural strong-motion data are being recorded by DWR.
Between the strong-motion and weak-motion sites, a total of 463 channels of seismic data are currently being recorded, with 343 channels (about 74%) now streaming into Earthworm in our Sacramento seismic lab. The remaining 123 channels of data record triggered data on site, and the data can be retrieved after the fact. These 123 channels will be added to the Earthworm stream as funding allows.
DWR plans to 1) upgrade many existing seismic sites with new seismic monitoring equipment, and 2) install more 4g strong-motion recorders to include monitoring of additional DWR facilities that are not currently instrumented, eventually bringing the number of streaming channels up to about 727 channels.
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