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Instantaneous outbursts in coal mines involve catastrophic and forceful expulsion of coal and large quantities of gas, creating a major mining hazard. Other researchers have studied relationships between coal outbursts and many geological factors, such as coal seam thickness, coal rank, coal seam age, current burial depth, and distance to plutons, with different conclusions for different coal fields and regions because of the complexity of the causative mechanisms. Coal outbursts nearly always have a close relationship to geologic structures; the present research was designed to determine the location and characteristics of specific danger zones associated with reverse faults.

Four coal mines in the Pingdingshan coal field, Henan Province, China were investigated in detail. Coal and gas outbursts associated with reverse faults nearly always occurred in the footwalls. Additional data were also used from two mines in Sichuan Province and one in Henan Province.

The first important observation of the geological structural phenomena was that coal seams in the footwalls of the reverse faults underwent greater tectonic deformation than those in the hanging walls. Coal lost its banded character and was physically transformed into microstructurally altered forms categorized as cataclastic coal, granular coal and mylonitic coal. Outbursts always occurred within a zone of this tectonically altered coal surrounding the fault. Second, the zone of tectonic alteration in the footwalls extended farther from the fault than that in the hanging walls. Third, where present in association with reverse faults, zones of higher coalbed methane content nearly always occurred in the footwalls. These three factors are the principal controls on coal and gas outbursts associated with reverse faults. Through their application, coal safety experts can narrow the predicted outburst danger zone to a smaller area.