A SEISMIC STUDY OF AN UNDERWATER CHEMICAL EXPLOSION: PROJECT AMCHITKA

An underwater chemical explosion was detonated 60 kilometers southwest of Amchitka Island on September 6, 1968. The device, which consisted of 250 tons of chemical explosives, was detonated at a depth of 3100 feet below sea level over the Aleutian Trench. Travel-time and amplitude data were recorded at seismograph stations throughout the United States and in Canada, Afghanistan, Australia, India, and Africa. Surface waves, however, were not detected. Travel times from the Amchitka explosion were late when compared to the P-wave arrivals from Longshot. The average body-wave magnitude for Amchitka, as computed from teleseismic data, was 4.6. Significant source bias for the explosion was difficult to observe due to the limited azimuthal control. Comparative data suggest azimuthal source effects are not as significant as those associated with Longshot.