Long-Period Horizontal Seismometer (WWSSN)

Description:

Working at the Lamont Geological Observatory, a Columbia University facility in Palisades, N.Y., Frank Press and his mentor, Maurice Ewing, designed seismometers that responded to surface waves of long-period and small-amplitude whether caused by explosions or by earthquakes. Their horizontal seismometer was of the “garden-gate” form: here, the horizontal boom attaches to the lower end of a vertical post, and a diagonal wire extends from the upper end of the post to the outer end of the boom. The first example was installed in 1953.

This example was made for the World Wide Standard Seismological Network. Established in 1961, the WWSSN was designed to detect underground nuclear tests, and generate valuable information about the earth’s interior and its dynamic processes. The WWSSN was a key component of VELA Uniform, a Cold War project that was funded by the Advanced Research Projects Agency (ARPA), a branch of the Department of Defense. It was managed by the U.S. Coast and Geodetic Survey and then by the U.S. Geological Survey. That agency transferred this instrument to the Smithsonian in 1999.

Each of the 120 stations in the WWSSN had two horizontal seismometers of this sort (one to capture the east-west component of the earth’s motions, and one to capture the north-south component). This example was used Junction City, Tx. It would have been linked to a matched galvanometer (such as 1999.0275.09) and a photographic drum recorder (such as 1999.0275.10). The “Sprengnether Instrument Co.” signature refers to a firm in St. Louis, Mo., that specialized in seismological instruments.

Ref: United States Coast and Geodetic Survey, Instrumentation of the World-Wide Seismograph System, Model 10700 (Washington, D.C., 1962).

W.F. Sprengnether Instrument Co., Inc., General Discription (sic) Long Period Horizontal Seismometer ([St. Louis], n.d.).

W.F. Sprengnether Instrument Co., Inc., Sprengnether Horizontal Component Seismometer, Series H ([St. Louis], n.d.).

Ta-Liang Teng, “Seismic Instrumentation,” in Methods of Experimental Physics, vol. 24 part B, Geophysics (1987), pp. 56-58.