Source depth of burial experiment at Shagan River, Kazakstan

摘要

The seismic field experimentation team at Los Alamos National Laboratory collaborated with Lawrence Livermore, the Defense Special Weapons Agency (DSWA) and the National Nuclear Center of the Republic of Kazakstan to record the Source Depth of Burial Experiment during the summer of 1997. A series of three 25 ton explosions at depths of 50, 300 and 550 meters along with associated 50 to 100 kg Green's function explosions and a 5 ton proof of concept explosion were instrumented at near source (0.1 to 20 km) and regional distances (100 to 1,100 km) using portable seismic data acquisition equipment. The near source data represent the first US recordings of seismic data at the former Soviet Union's Semipalatinsk nuclear test site. The main objective of the Depth of Burial Experiment was to test whether source depth can help identify underground nuclear explosions from observations at distance ranges of 100--1,000 km. A secondary objective was to help calibrate the Kazakstan seismic network, especially the primary IMS station at Makanchi and the auxiliary IMS stations at Kurchatov and Aktyubinsk. Near-source records show the 50 m deep explosion generated much higher amplitude surface (R(sub g)) waves than did either of the deeper explosions. Impulse P-wave arrivals dominated the traces from the 300 and 550 meter deep explosions. P-wave amplitudes, 10--20 Hz, appeared to be a stronger function of source than of path or site. Apparent P velocity was highly path dependent, with higher velocities parallel to the local, NW-SE fabric of the geologic structure. Empirical Green's function results for the 25 ton shots show increasing corner frequency with depth, consistent with predictions of the Mueller-Murphy source model.