A series of three large-scale underwater chemical explosions of 0.5 ton, 2 tons and 5 tons of Chenamon (ANFO-like slurry explosives) were detonated in the Dead Sea at a water depth of 70 m, during November 1999. The main objective of the experiment was calibration of seismic stations in the Middle East that provide monitoring of underground nuclear tests, using accurate travel times of seismic waves. The largest shot produced a seismic magnitude of about 4, and was recorded at distances up to 3500 km. Results of a study of hydro-acoustic effects and source phenomenology features of underwater explosions are presented.
The video-records and audio tracks demonstrated interesting physical phenomena, such as a “cavitation hat”, epicenter plume, arrivals of hydro-acoustic blast waves and bubble pulsations in air-acoustic waves. Recordings of pressure-time history for the two larger explosions at distances of about 700 m revealed several phases, propagating by different paths. Arrival time measurements contributed to verification of the charge depth, explosion-to-sensor distances, and first bubble-pulse period.
The peak pressures of the water shock waves observed significantly exceeded the values expected from a similar TNT charge in ocean water. This fact can be attributed to the unequaled acoustic impedance of the Dead Sea water, being about 40% higher than in the ocean.
The measured near-source hydro-acoustic observations were utilized to estimate source parameters of the 2 and 5 ton explosions. Based on the curve-fit equation of the pressure-time measurements, the direct shock wave energy was estimated to be 27.5% of the total available explosive energy. The charge TNT equivalent was determined, corresponded to the manufacturer’s estimate of the Chenamon energy as ~80% of TNT.
