SHIST (Seismic Hard rock In-Situ Source Test)
In 1993, a test that would generate seismic data from a simulated nuclear explosion contained in hard rock was approved for SHIST Site for a test approved to occur in 1994. This test however, was ultimately not conducted, and SHIST was converted to a rock penetration test site. Alt. SHIST was recognized as a possible test site in 1993, although SHIST was the preferred site based primarily on existing access routes. Alt. SHIST was eventually used as a test site for conducting earth-penetrating tests similar to those conducted at SHIST.
A Shist is a fine grained banded metamorphic rock such as mica, in contrast to a Gniess such as granite, which is a course grained banded metamorphic rock. Metamophic rocks are formed after preexisting rock material has been changed chemically and/or physically in response to changing temperature and pressure conditions. By definition metamorphic rocks do not undergo melting. Rocks that melt become magma and eventually igneous rock.
SHIST (Seismic Hard rock In-Situ Source Test) was a proposed prototype High Explosive (HE) seismic source function experiment designed to provide a benchmark data set for seismic source function models in hard rock geology and also to provide a threshold of detection calibration point for regional seismic monitoring systems. The experiment was to consist of 20 tons of HE in a fully contained sphere detonated in a granite test bed. The test was subsequently canceled.
Preliminary material models were developed for the site and 1 D and 2D finite difference scoping calculations performed to serve as a starting point should the test (or other HE test requiring a hard rock geology) be revived in the future. The intent was to investigate the details of the shock wave propagation into granite, and to determine the seismic transition point (the range at which the stress wave developed by the HE source began to decay as an elastic wave) to assist with gage placement activities. 3D effects, such as the surface slope variation and ground fault lines, found to exist at the proposed SHIST Site, were neglected.
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