SPACE-TIME CORRELATIONS OF B-VALUES WITH STRESS RELEASE

A total of 1503 events for a 2-month period associated with a m(N) 2.6 rockburst is investigated for possible space-time correlations betwee n low magnitude (-1.1 to -0.4) b values and several estimates of stres s (static stress drop, apparent stress, and dynamic stress). Spatial v ariations of decreasing b values were found to be well correlated with increasing stress release estimates for time intervals prior to the r ockburst and following the aftershock sequence. The strongest correlat ion to b value was with the dynamic stress drop, having correlation co efficients of 0.87 and 0.79 for the two intervals, respectively. The r ockburst was found to actually occur at the intersection of the spatia l coordinates corresponding to the largest gradient in b value. Based on these correlations, we conclude that the low magnitude seismicity i s an indicator of the stress state within the rock mass, and can be us ed to study and forecast stress patterns in the vicinity of an impendi ng major event. Time variations, however, did not show the same clear correlations and these are discussed in terms of departure from steady state conditions. Regardless, our results favour the use of b values in a spatial context rather than in a time analysis approach, and we c onsider that b values provide valuable information regarding the chang ing stress conditions within the seismogenic volume.