Monitoring the sounds of silence.

Monitoring the sounds of silence

In February, the Soviet Union permitted U.S. scientists toinstall a second phase of seismic monitoring equipment near the Soviet nuclear testing site in eastern Kazakhstan. This installation is part of a cooperative project between the Soviet Academy of Sciences and the private, Washington, D.C.-based Natural Resources Defense Council (NRDC) to demonstrate that seismic equipment can reliably verify whether nuclear tests are being conducted--a provision that would be an important part of a future ban on nuclear testing.

Also as part of the agreement, the first phase of identicalmonitoring equipment was installed at the same time near the U.S. testing site in Nevada. Scientists from both sides had planned to work together in the construction and operation of each of the sites. However, diplomatic problems have thus far prevented Soviet scientists from helping in Nevada.

The project began last year during the unilateral Sovietmoratorium on nuclear testing (SN: 7/26/86, p.55). Since the resumption of testing, the Soviets have enforced a longstanding policy of secrecy by requiring NRDC to turn off the equipment for the duration of the blasts. However, even without measuring the actual explosions, U.S. scientists will be able to use data from these seismometers to indirectly determine the strength of Soviet tests, says Holly Eissler from the Scripps Institution of Oceanography in La Jolla, Calif.

Soviet tests are routinely recorded by seismometers aroundthe world. But lack of knowledge about the geology of the Kazakhstan test site limits how accurately scientists can estimate the yield of these explosions, says Eissler, who is a member of the U.S. team that constructed the Soviet stations.

By recording mining blasts from quarries located near thetest site, U.S. scientists can infer details about the local rock, as well as learn how seismic waves attenuate when they pass through that site.