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 History of Earthquake Engineering

Earthquake Engineering began as a small unit in the Division of Planning between 1960 and May 1963. The first seismographic stations installed by DWR were in the north, near what is now Oroville Lake and Dam. At the time of construction not much was known about reservoir induced seismicity. It was known that under certain conditions, filling a reservoir could generate earthquakes. Monitoring the seismicity around the DWR lakes and reservoirs was important. Monitoring the area for earthquakes before the dam was constructed would provide background seismicity for comparison with seismicity after impoundment. This way, any changes due to the reservoir filling could be detected.

As construction of the State Water Project progressed, other seismographic stations were installed near planned storage facilities. By 1972, DWR was operating eight stations. These were ORV, MGL, and KPK near Oroville Lake, SLD near San Luis Dam, PYR between Pyramid Lake and Castaic Lake, CSP and MRD near Silverwood Lake, and PEC near Lake Perris. This data was shared with Cal Tech, UC Berkeley, USGS, and Univ.of Nevada, Reno. These organizations in turn shared selected stations they operated. As of 1996 DWR records 80 channels of real time seismic data used to locate earthquakes throughtout the State Water Project and Sierra Nevada Mountains. The Division of Safety of Dams uses the information to determine when inspections of dams are required.

All 80 channels of data are continually monitored by a computer program in the Earthquake Engineering room in the Resources Agency Building in Sacramento. When an earthquake occurs, the program automatically locates the epicenter and determines a magnitude. If the magnitude is above 3.7, the program alerts the seismologists by means of a pager. The pager shows the magnitude, epicenter co-ordinates, time and day of the earthquake. The seismologist then can log onto the computer at the Resources Agency and verify the location and magnitude. Within 10 minutes, POC can be notified as to the correctness of the earthquake parameters computed.

 


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