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Assessing the Nation's Earthquakes The Health and Future of Regional Seismograph Networks (1990) / Chapter Skim
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5. The U.S. National Seismic Network
Pages 32-37

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From page 32...
... The immediate objective of this cooperative effort is to establish a network of some 60 modern seismograph stations more or less evenly spaced throughout the United States east of the Rocky Mountains with satellite communications links to the NEIC. The ultimate goal of the effort is to record ground motion across a wide range of frequencies and with high dynamic range from all earthquakes nationwide above magnitude 2.5-3.0.
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From page 33...
... Other important uses for which high station density is essential include earthquake hazard mitigation, earthquake prediction, estimation of strong ground shaking, and studies of the earth's crust and deep interior. DESIGN OBJECTIVES The USNSN is being designed to meet the following objectives: · Detect and locate all earthquakes of magnitude 2.5-3.0 or greater within the United States; · Report to the public all earthquakes of magnitude 2.5-3.0 or greater within the United States within 30 minutes; · Minimize network development risk and cost Minimize operational cost of the network; Locate the stations where the seismic "noise" is low; a Measure the seismic signals over a wide range of frequencies and amplitudes; and · Provide rapid distribution of the data products.
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From page 34...
... Only a few of these sites are fixed to date, but Figure 5 gives an idea of the station distribution and spacing that might be expected. The average station spacing is between 350 and 400 km, with a denser concentration of stations in the seismically active areas of the eastern and western United States.
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From page 36...
... Other functions include maintaining an archive of waveform data with associated epicenter information, providing an interactive capability for a seismologist to review automated results, and producing final epicenter catalogs. In addition to epicenter catalogs, compact disks with read-only memory (CD-ROMs)
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From page 37...
... One of the major advantages of a satellite-based system over land-link telemetry is the flexibility of station siting: the dual limitations of line-ofsight links for radio transmission or availability of telephone line drop points are eliminated. The beneficial result is that station sites can be selected on the basis of low background noise or optimum station distribution rather than data transmission feasibility.
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Key Terms

  • regional seismic
  • seismic networks
  • seismic data
  • national seismic
  • existing regional

  • rocky mountains
  • nuclear regulatory
  • completed nationwide
  • processing facility
  • regulatory commission

  • data processing
  • strong ground
  • data transmission
  • eastern united
  • rapid distribution

  • central processing
  • seismic stations
  • satellite communications
  • include verifying
  • seismic signals

  • network available
  • low background
  • western united
  • global seismic
  • reduced funding

  • error correction
  • interactive capability
  • includes error
  • communications links
  • record ground


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