In-situ measurement has been carried out at Sunagawa Coal Mine to study the seismicity in two mining panels; in the first panel the extraction ratio amounted to 77%, on the contrary in the second panel coal pillars were so extensively left that the extraction ratio was 48%. Magnitude distributions of seismic events were followed by the Gutenberg-Richter's formula, log N=a-bM, in which the b-value was the same for two mining panels but the a-value was lower in the panel whose extraction ratio was lower. Spatial rates of seismic energy were 87.4 and 38.4J/m2 in the first and second panels respectively.
On the other hand energy release rates associated with mining were determined from the Face Element Method as 1.20 and 0.57MJ/m2 in the two mining panels respectively. It was, therefore, concluded that spatial rate of seismic energy was in proportion to energy release rate presumed from an elastic model. Furthermore it was suggested that a slight decrease in extraction ratio might be effective to reduce the hazards of rockburst as well as stowing with wastes and packing with artificial materials.
