Abstract

We perform calculations of an explosion in 3D prestress field and examine the effects on near‐field data, regional data, surface waves, and far‐field body waves. We specifically model the nuclear explosion Shoal, which had anomalous near‐field ground motion. The calculation of Shoal shows that tectonic strain release consistent with the local stress state can generate near‐field and regional signals, including long‐period surface waves, similar to those observed. We find that tectonic release causes small changes to the far‐field P‐wave waveform but has very little effect on far‐field P‐wave amplitudes. It does generate SH waves not present in the calculation without tectonic release. This implies that whereas tectonic release may significantly affect Ms, the effect on mb is small. Nonlinear effects above the explosion have a stronger effect on body waves than tectonic release, with the main effect being a reduction in the pP amplitude.

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