Theoretical signature of a cavern created by an underground nuclear explosion in 2-D exploration seismic data

Abstract

SUMMARY The proliferation of nuclear tests is a problem that threatens the safety and health of everybody. In order to tackle this problem, the UN is promoting the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which includes protocols for monitoring and On-Site Inspections (OSI). The purpose of OSI is to verify if a nuclear test has been carried out by identifying with a geophysical technique the presence of a cavern, hole or some device that indicates the violation of the treaty. In this context, it is desirable to be able to use exploration-seismology techniques to detect caverns created by an underground nuclear explosion. However, there is scarce information about the seismic signature of this type of cavern. We present the results of elastic wave propagation simulations, in the time domain, with a cavern created by an underground nuclear explosion. The wave equation is solved using the spectral element method with 4th order basis functions and quadrilateral elements. We show the results for models with cavities and caverns corresponding to explosions of 1, 20 and 100 kilotons, and obtain seismic traces in which we can observe the effect of the structures. We conclude that caverns created by nuclear explosions can be detected using seismic data and distinguished from caves because they behave like two concentric diffractor bodies, as opposed to caves-like diffractors.