Monitoring Routine Mine Seismicity in the Conterminous United States

摘要

We are applying standard U.S. Geological Survey/National Earthquake Information Center (USGS/NEIC) earthquake detection and location methodologies to monitor routine mine seismicity in the conterminous U.S. Our principal goal is to develop knowledge of mining seismicity in districts from which teleseismically recorded mining associated seismic events might occur. This knowledge would provide a basis for understanding future seismic events from these mining districts that might be located by the International Data Center(IDC) after entry-into-force of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Epicenters are calculated from the arrival-times of seismic phases, and their accuracies vary according to the distribution of seismographic stations in the regions in which the mines are located. 90% confidence ellipses on epicentral coordinates are given. Although the USGS/NEIC does not obtain 'ground truth' information from mining companies about most individual mining events, knowledge of mine locations and mining practices enables us to evaluate the reliabilities of the epicenters and confidence ellipses for many regions. The confidence ellipses represent location accuracies quite well for most of the mining districts. Plotting only events with small confidence ellipses dramatically reduces the scatter of epicenters. Problems with the mining-event confidence ellipses are typical of problems associated with confidence ellipses in general: the level of confidence associated with the ellipses must be viewed as being somewhat lower than the nominal 90%; there is evidence of substantial (up to 20 km) location bias for events in a few of the districts; ellipses associated with poorly recorded events are particularly prone to misrepresentation of location accuracy.