Accurate Locations of Nuclear-Explosions in Balapan, Kazakhstan, 1987 to 1989

Locations of 20 nuclear explosions from 1987 to 1989 at the Balapan test site, Kazakhstan, are derived with a precision of about 100 m from time-sequence SPOT satellite images combined with telescismic epicenter estimates. For most events, there is little or no ambiguity in the association between seismic events and image features. The locations determined by JED are associated with formal error estimates (95% confidence ellipses) that are significantly too small. In 16 out of 19 cases, the events are found from satellite imagery to lie outside these ellipses. Possible causes are nonuniform observation, poor azimuthal coverage, and source region heterogeneity. Our results should prove valuable for studies of seismic waveforms, arrival time and amplitude tomography, event location, tectonic release, and seismic coupling at Balapan, and demonstrate the utility of combined seismic and satellite image analyses for seismic verification studies.