Utilization of Seismic and Infrasound Signals for Characterizing Mining Explosions

This empirical study is designed to quantify mining explosions as sources of seismic and infrasound signals. The study focuses on the Western US, where a variety of different types of mining operations exist, ranging from surface coal cast blasting to hard rock fragmentation blasting in porphyry copper mines. The study is extended to the taconite mines of the Mesabi Range of Minnesota. Newly installed instrumentation, including in-mine equipment for ground truth as well as regional seismo-acoustic deployments to complement existing resources in the region, is a key component of the study. In-mine monitoring is ongoing at the Morenci Mine in Arizona and the Tyrone Mine in New Mexico. The seismo-acoustic station at Ft. Hancock, Texas, and the infrasound upgrade to Tucson, Arizona, and WUAZ will also be illustrated. Data from this study have been used to address coupling and source characterization issues for both seismic and infrasound signals. The seismic coupling of large-scale cast blasts in Wyoming, copper fragmentation blasts in Arizona and New Mexico, and taconite fragmentation blasts in Minnesota are compared. For all these event types, there is no relation between total explosive yields and peak amplitude either in the mine or at regional distances. A series of contained, single-fired explosions of varying yield was conducted in the coal mine. At regional distances these events, in contrast, show a definitive magnitude-yield relation that follows the relationship for nuclear explosions. These data and an extensive modeling exercise suggest that the complete characterization of the delay firing process, including a spall contribution, can explain the regional observations. Acoustic data from within the mine indicate that a relation exists between total explosive weight and peak acoustic amplitudes. At regional distances, under optimum wind conditions, approximately 25% of Morenci Mine shots are observed out to 500 km.
Presented at the Seismic Research Review: Worldwide Monitoring of Nuclear Explosions (23rd) held in Jackson Hole, WY on 2-5 October 2001. Published in the Proceedings of the Seismic Research Review: Worldwide Monitoring of Nuclear Explosions (23rd), p550-558, 2001.