Spatiotemporal analysis of elastic and inelastic deformations in roof-rocks from seismological observations

Abstract

The spatiotemporal analysis of seismic zones characterised by the scattering and accumulation of strain energy in the roof-rocks of the excavated longwall panel where inelastic or elastic deformations occurred during hard coal seam mining is discussed. The studied longwall panel was designed to utilize the effect of partial stress relaxation caused by the earlier extraction of the coal seams located above. A full seismic moment tensor and spectral source parameter analyses were used to obtain information about the degree of inelastic and elastic coseismic deformations. This study also showed that these deformation changes correspond to variation in the Benioff strain release characteristics. Next, analyses of deformation zones were compared with the relationship between radiated energy and the excavated volume of rocks per month. The concept of balanced seismic energy release assumed the exponential increase of released seismic energy with the increase in the volume of excavated rock. Discrepancies between the observed and predicted radiated energies indicated that strain energy in selected zones in the rock mass was either scattered if the prediction was overestimated, or accumulated if underestimated. Moreover, the study showed that elastic deformation in one zone can lead to inelastic deformation in the same zone.