Forensic seismology originated during the Cold War as a means of monitoring the enemy's underground nuclear tests. But it is a field whose uses are as broad as the imagination.
FOR EXAMPLE:
Forensic Seismology Provides Clues To Kursk Disaster
ScienceDaily (Jan. 23, 2001) — WASHINGTON - The explosions that sank the Russian submarine Kursk on August 12, 2000, triggered shock waves that were recorded by a network of seismic stations in the Baltic region and beyond. Now, forensic seismologists have used these data to reconstruct the disaster. Writing in the January 23 issue of Eos, the weekly newspaper of the American Geophysical Union, Keith D. Koper and Terry C. Wallace of the University of Arizona and Steven R. Taylor and Hans E. Hartse of the Los Alamos National Laboratory report that, based on their analysis of seismograms, explosions, not impact, caused the Kursk to sink with the loss of all crew members.
The authors note that underwater explosions are highly efficient producers of seismic signals, and these have been long studied, including those generated by the sinking of a Soviet submarine in 1989. The Kursk seismic data possess features unique to underwater explosions, a strong indication that the Kursk did not sink because of a collision or other impact, they say.
Seismic stations recorded two explosions that correspond to the Kursk disaster in time and place. The first explosion was 250 times smaller than the second one, which occurred 135 seconds later. The earlier explosion was clearly recorded only at a few nearby stations, while the second one released energy equivalent to around five tons of TNT and was recorded up to 5,000 kilometers [3,100 miles] away.
Koper and his colleagues note that this area of the Barents Sea rarely experiences any seismic activity, so it was highly unlikely that the seismic signals were caused by an earthquake. One point of careful analysis, they say, concerned whether the second event consisted of one massive explosion or several simultaneous smaller ones and perhaps also impact of the Kursk on the seafloor.
The most compelling seismic evidence that the main Kursk event was dominated by an explosion was the observation of a "bubble pulse." This pulse results from oscillations of a bubble of hot gases unleashed by an explosion as it rises toward the surface. The spectral pattern produced by an underwater explosion and recorded by seismic stations provides strong evidence that the second explosion was one massive event, not several smaller ones.
In another study, Wallace and Koper collaborated to use seismic data from Norway, Sweden, Finland, and Spitsbergen to reconstruct the sinking of the Russian submarine Kursk on 12 August 2000.
When the sub sank, the Scandinavian seismometers showed two events a little more than two minutes apart. Underwater explosions produce bubbles of hot gases, which oscillate as they rise.
The frequency of these oscillations depends on the size of the explosion and the depth at which it occurs. This allowed the scientists to determine that the Kursk was sunk by an explosion, not a collision, and that it had occurred when the sub was at a depth of 83 m.
The first blast carried power equivalent to 250 kg of TNT; the second was several times larger. Wallace and Koper therefore suspected that the first was a torpedo misfire during live-fire exercises, which the Kursk was known to be undertaking at the time. The second, larger explosion, they believed, probably occurred when fire from the initial accident detonated additional warheads.
Shortly after the sinking, the seismograms revealed many other small seismic events, with magnitudes between 1.25 and 1.86. These appear to have been depth charges dropped by the Russians to discourage other nations from sending scuba divers to spy out the secrets of the stricken submarine. The seismic readings were so precise that Wallace and Koper could even track the speed and course of the naval vessel used to lay down the underwater barrage.
