NON-SIMILAR FREQUENCY-MAGNITUDE DISTRIBUTION FOR M-LESS-THAN-1 SEISMICITY

A series of 1503 induced seismic events ranging in magnitude from -2 to 1 as computed based on a locally calibrated seismic moment scale were located within a well-defined volume at depth. The seismicity analysis was carried out over 2 months and included events recorded before, during, and following the after-shock period of a m(N) 2.6 rockburst. A non-similar pattern was clearly apparent for both cumulative and non-cumulative frequency-magnitude distributions, showing a relative enhancement of seismicity between magnitudes -0.5 and 0. This supports the existence of nonsimilar scaling at these magnitudes. The time variation of the b-value, as computed for a limited self-similar magnitude domain (-1.1 to -0.4), did not appear to be related to the rockburst. Instead, it is suggested that the rockburst perturbed the local stress field and consequently the distribution of the very small events. No correlations were found between b and space clustering.