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PNSN Strong Motion Network

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PNSN Strong Motion Station Installation

Strong motion instruments are those that will record ground motions from the largest earthquakes without any waveform distortion. Having high-dynamic range they can also record ground motions from earthquakes down to magnitude 3.0, or even smaller, within 100 km of the instrument. Specifications for new sites in the Pacific Northwest are loosly based on the Minimum Specifications for TriNet Reference Strong Motion Stations developed for use in California.

We are interested in sites that are considered "free field" and "reference" sites. A "free field" site is one that is located away from all buildings or other strutures and where the instrument is buried in a shallow hole or vault. "Reference" sites are either in or near a small building of low height (1 or 2 story) with the instrument located in the basement or ground floor. Buildings covering less than 6,000 square feet are preferred. The instrument will be bolted down.

Ideally the instrument will be located as far as possible from seismic noise sources such as fans, motors, pumps, heavy doors, vehicle traffic, and so on. It also must not be near any objects which could easily fall over or slide into it during a strong earthquake.

Technical needs include AC (110 V) power and Ethernet for a connection to the public Internet or gateway to the University of Washington network. Data produced by the stations is telemetered at a rate of about 1400 Bytes/sec or about 3 Internet packets per second and is constant at all times (significantly lower rate than most home dial-up Internet connections).

Technical Needs Summary

Technical siting specifications are summarized in the table below.

Component Technical Needs
GPS Antenna
  • mounted outside, usually on exterior wall close to roof line
  • cable will need to be routed from antenna to seismograph
  • maximum distance from seismograph to antenna must be less than the cable length of 65 ft.
Sensor/Seismograph
  • installed in external vault (diagram) (photograph)
    OR
  • mounted inside building (diagram)
    • bolted to level concrete floor
    • located in basement or ground floor of low (1 or 2 story) building
    • seismically quiet location (no motors, fans, pumps, etc nearby)
Internet-interface
  • IP address should be assigned prior to installation
  • RJ-45 type 10Base-T Ethernet connection
  • AC power
UW Data Acquisition
  • UW access through firewalls to specified IP address and port number
  • data are acquired on computers dedicated to seismic data acquisition and are maintained at a high security level

A Graphical System Overview is also available.

Updated August 7, 2002

Strong Motion Home Page Graphical System Overview

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