Tectonic release from the Soviet Joint Verification Experiment

Abstract

The regional broadband seismic recordings of the Soviet Joint Verification Experiment underground nuclear explosion show evidence of tectonic release in the form of Love waves at long periods and high‐frequency SmS phases on the transverse components. We present the results of some simple forward modeling of this data in order to quantify both the moment and mechanism of the tectonic release. Using 10–20 second Love wave amplitude and phase data, we estimate the tectonic release moments to be 3.5 × 1015 N‐m for a north striking right‐lateral strike‐slip fault, and 7.0×1015 N‐m for a northwest striking reverse fault. Using the results of these end member tectonic models, the Rayleigh waves can be satisfied with explosion moments of 1.7×1016 N‐m (F=0.31) and 2.4×l016 N‐m (F=0.44), respectively. To resolve the ambiguity in tectonic mechanism we used the reflectivity method to generate synthetics and compare the relative amplitudes of the SH and SV parts of the SmS phase. While the results favor the strike‐slip mechanism of tectonic release, application of source inversion techniques to this data and other regional data will be needed to evaluate more realistic tectonic release models involving, for example, oblique fault slip and dip.