Program element: IV, Providing Real-time Hazard and Risk Assessment
Key words: Strong ground motion
October 1, 1996 - September 30, 1997
The Pacific Northwest Seismograph Network (PNSN) operates seismograph stations in Washington and Oregon, and collects and analyzes earthquake data. In May of 1996 the US Geological Survey (USGS) funded the PNSN to begin a pilot project of modern strong-motion instrumentation in the Puget Sound urban area. Three sites were funded under this grant, and three under joint operating agreement 1434-95-A-1302, "Pacific Northwest Seismograph Network Operations".
Five wide-dynamic-range strong-motion IDS-24 accelerograph units produced by Terra Technology Inc. of Redmond, Washington have been installed, and data from four of the strong-motion instruments are currently telemetered in real-time to the PNSN. The final site will be installed be the end of 1997. Table 1 lists strong-motion, three-component stations operating in Washington and Oregon that provide data in real or near-real time to the PNSN. Several of these stations also have broad-band instruments.
The PNSN strong-motion network should eventually cover the urban corridor from Eugene, OR to Bellingham, WA, and include rapid calculation and broadcast of strong-motion earthquake parameters. The PNSN is working with regional utilities and industries that can provide assistance in siting, telemetry, instrumentation or cooperative operations.
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TABLE 1
Strong-motion three-component stations operating at the end of the 3rd quarter 1997.
The "SENSOR" field designates what type of seismic sensor is used;
A = Terra-Tech SSA-320 SLN triaxial accelerometer, BB = Guralp CMG-40T 3-D
broadband velocity sensor.
The "TELEMETRY" field indicates the type of telemetry used to recover the data.
C = continuously telemetered via dedicated telephone lines, D = dial-up.
_STA__LAT_________LONG_________EL______NAME_ ______SENSORS__TELEMETRY
MPL 47 28 08.2 122 11 06.2 0.122 Maple Valley A C,D
QAW 47 37 53.2 122 21 15.0 0.140 Queen Anne A C
SEA 47 39 18.0 122 18 30.0 0.030 Seattle A,BB C,D
SPW 47 33 13.3 122 14 45.1 0.008 Seward Park A,BB C
UPS 47 15 56.1 122 28 58.4 0.113 U. Puget Sound A D
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The M 4.9 June 23 Bremerton earthquake was the first event large enough to trigger the PNSN strong-motion network. Preliminary peak ground accelerations ranging from 0.0015 g to 0.0023 g were recorded at 3 strong motion sites. In this case, the strong motion stations happened to be nearly at the edge of the felt area. Closer to the epicenter, a broadband seismometer (GNW) recorded an acceleration of 0.0095 g.
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UW GEOPHYSICS PROGRAM ..... SEISMOLOGY INFO..... PNW EARTHQUAKES