World-Wide Standardized Seismograph Network

In the early 1960s the United States put identical seismographs, calibrated the same way, in more than a hundred places around the world and published the records on film for anyone to copy. It was built to detect nuclear tests and ended up helping to prove plate tectonics.

Born of a test-ban problem

Verifying a ban on nuclear tests means telling underground explosions from earthquakes at a distance. A 1959 panel chaired by Lloyd Berkner recommended a research programme, Project Vela Uniform, and with it a worldwide network of standard seismographs. The Albuquerque Seismological Laboratory opened in New Mexico in 1961 to run it, and the first station, ALQ, was installed that year.

By 1965 some 111 stations had been installed, in about 60 countries, and the last installation was completed at Brasília in 1971. The US Coast and Geodetic Survey ran the network at first and the USGS from 1973.

Standard instruments, shared records

Each station carried the same set: three short-period and three long-period seismographs, identical in design and calibrated to the same standard. Because the instruments were alike, a record from Nairobi could be compared directly with one from Honolulu. The paper and film records were copied to a central archive, and copies were sold to researchers at the cost of copying, an early example of open data in the geosciences.

The data proved decisive in the 1960s revolution in earth science. Seismologists such as Lynn Sykes used the WWSSN's clear first-motion records to show that earthquakes along ocean ridges had the mechanism of transform faults, as plate tectonics predicted, and the pattern of deep earthquakes outlined subducting plates.

An end and an inheritance

The network was terminated in 1996, replaced by the digital Global Seismographic Network. Its legacy is a standard: a single type of instrument, calibrated and documented, deployed widely and sampled openly. Its film archive has since been scanned, and the records are still used to study old earthquakes.

A network designed for one goal and used for another

The WWSSN was funded to detect nuclear tests, a national-security goal, but its open data made it the instrument of plate tectonics. That outcome was neither planned nor prevented, and it set a pattern for civil use of defence-funded observation: GPS, weather satellites and the seismic networks all began in that way. The standardisation of the instruments was a cost accepted for the sake of verification, and became a benefit for science. The archive of film chips remains in use for the study of historical earthquakes, including events in the 1960s that modern networks did not record.

Instruments and technologies

  • Short-period seismograph A Benioff electromagnetic seismometer with a period of about one second, sensitive to nearby and high-frequency signals, recorded on photographic paper.
  • Long-period seismograph A Sprengnether or Press–Ewing instrument with a 15-second period, sensitive to surface waves from distant earthquakes.
  • Station time standard Crystal clocks and radio time signals kept the station's time to a fraction of a second.

The people

  • Lloyd Berkner Physicist who chaired the 1959 panel recommending the network.

Timeline

  • 1959 The Berkner panel report leads to Project Vela Uniform.
  • 1961 The Albuquerque Seismological Laboratory opens and the first station (ALQ) is installed.
  • 1965 111 stations installed.
  • 1971 Final installation completed at Brasília, Brazil.
  • 1973 Operations transfer to the USGS.
  • 1996 The network is terminated.

Key lessons for observation today

  • Identical instruments make a dataset A common design and calibration turned a hundred stations into one instrument. This is the strongest argument for standard qualification of sensors.
  • Share the record at cost Selling copies at cost let researchers around the world use the data, and made discoveries nobody planned. Open access multiplies the return on observation.
  • Documentation is calibration Each station's response was documented. Instrument response metadata is what makes data from different places comparable.

Sources

  • USGS Fact Sheet 2011–3065, Albuquerque Seismological Laboratory: 50 years of global seismology
  • Wikipedia, World-Wide Standardized Seismograph Network (secondary)
  • USGS earthquake monitoring