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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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