Microseismic Monitoring of a Longwall Coal Mine. Volume I - Microseismic Field Studies

摘要

This report is volume 1 of a three-volume report on the microseismic monitoring of longwall coal mines. Volume 1 deals mostly with the detailed aspects of the microseismic field study; however, brief references are made to other secondary studies described in volumes 2 and 3. During the field study, a mobile microseismic monitoring facility and associated transducers were employed to detect and record microseismic activity above a longwall panel at Greenwich Collieries, Barnesboro, PA. The fundamental objectives of the study were (1) to evaluate the feasibility of detecting microseismic activity originating from longwall mining operations using an approximately planar, near-surface, geophone array installed above the longwall and (2) to attempt to locate the sources of the various microseismic events. The investigation proved, that using the techniques developed, it is possible to detect microseismic events at depths of more than 400 ft and at horizontal distances in excess of 800 ft from the source. The majority of the events had frequencies on the order of 10 to 100 Hz, and particle velocities of 50 to 300 microips. When a suitable velocity model was used, most of the events located were computed to be within + or - 100 ft vertically of the coal seam and + or - 50 ft horizontally of the longwall face.