Rockburst Research Applied to Nuclear Event Discrimination

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per respo gathering and maintaining the data needed, and completing and reviewing the collection of inforr-* collection of information, including suggestions for reducing this burden, to Washington Headqua Davis Highway, Suite 1204, Arlington, VA 22202-4302, and Rockbursts produce seismic signals that are similar to those associated with near surface earthquakes and explosions. Some o: the methods developed for source mechanism studies also encompass imaging techniques appropriate for nuclear event verification, and, as a result, have implications for the Comprehensive Test Ban Treaty (CTBT). Past experiments have demonstrated a clear relationship between Barkhausen Noise (BN) and stress in pipeline steel samples. Stress can affect the nature of the pinning sites at domain boundaries which in turn plays a role in the way that domain walls move and cause BN pulses. We have conducted experiments to detect a relationship between BN and stress in magnetite-rich rocks. These experiments were performed by applying uniaxial loading from 4500N to 55000N to cylindrical core samples of magnetite-rich rocks obtained from the Stillwater Complex in Montana. A pick-up coil was used to detect the BN pulses and an electromagnet was used to magnetize the samples. BN pulses were recorded during a specified time interval for each increment of loading. The pick-up coil was positioned to be near magnetite-rich regions of the sample. We have observed a linear increase in the number of BN pulses with increased loading. Ongoing research is focused on refining the experimental procedure to increase the bandwidth of recording and eliminate possible sources of noise in the experiments. The results of this study might help us to understand the nature of the remagnetization that often accompanies large-scale tectonic events. Moreover, this study could lead to a method of nondestructive testing to determine state of stress at mine walls. MQOQttO I5(j SUMMARY The basis for this research is that rockbursts produce seismic signals that are similar to those associated with near surface earthquakes and explosions. A complete understanding of source mechanisms is necessary for the correct identification of these events. Some of the methods developed for source mechanism studies also encompass imaging techniques appropriate for nuclear event verification, and, as a result, have implications for the Comprehensive Test Ban Treaty (CTBT). SUBJECT TERMSPCI/Atlantic Scientific INSAR software was purchased last fall for elevation change detection at a rockburst site using radar interferometry. We have been familiarizing ourselves with this software and radar remote sensing. Images have recently been acquired that cover the site of a large rockburst.The air wave can interfere with the rock wave in Ground Penetrating Radar (GPR) transillumination experiments making it difficult to pick the rock wave first arrivals in mines. This was particularly a problem at small t...