Evaluating Seismicity at Underground Coal Mines Using Temporary Surface Geophone Deployments Available to Purchase

Monitoring mining-induced seismicity can provide valuable insights into the rock mass response to mining. There are many approaches to monitoring seismicity in mining depending on the mining method, mining geometry, data quality requirements, and acceptable cost of monitoring. One flexible, inexpensive monitoring method is a temporary surface seismic deployment. The National Institute for Occupational Safety and Health has conducted temporary deployments above longwall panels at two longwall coal mines in the western United States. This study evaluates the effectiveness of these deployments in meeting basic monitoring objectives and examines the seismicity recorded at each mine. A total of 901 events were detected at the first mine and 30 events were detected at the second mine. Event magnitudes ranged from 0.1 to 1.6 for one mine and from 0.4 to 0.7 at the other. The two deployments were successful in their goals; however, the results highlight the importance of well-designed arrays and accounting for seismic velocity changes caused by mining. Although the deployments only lasted a few weeks, notable seismic features of each panel were observed. The two mines exhibit starkly different responses to similar mining methods, quantified by the rates, magnitudes, and locations of the events.