%A Konstantinos Michail Leptokaropoulos
%A Monika Staszek
%J Acta Geophysica
%T Temporal response of magnitude distribution to fluid injection rates in The Geysers geothermal field
%X The influence of fluid injection rates on the magnitude distribution of the seismicity which occurred in the NW part of The Geysers geothermal site is studied here. A direct comparison between injection rate changes and b value response is attempted after appropriate selection of data subsets. Due to the relatively small sample (1121 events, corresponding to an average rate of ~ 0.45 events/day), we also aggregated seismic activity into two families corresponding to increasing and decreasing injection rates, respectively. The b values were calculated as a function of time lag related to the injection activity. In agreement with previous studies, we found a statistically significant direct relation between b values and injection rate changes, which occurred at a zero or very short time lag (from 0 to ~ 15 days). However, the b value changes are related to the slope (i.e., the second derivative of injection volume), instead of the absolute values of injection rates. The increasing injection rates correspond to b = 1.18 ± 0.06, whereas the decreasing injection rates correspond to b = 1.10 ± 0.05. The corresponding values estimated by the repeated medians technique are b = 1.97 ± 0.20 and b = 1.50 ± 0.13. Both differences are significant at 0.05 level.
%N 1
%K Injection-induced seismicity Magnitude distribution Geothermal fields Statistical seismology
%P 327-339
%V 67
%D 2019
%I Versita, Warsaw and Springer-Verlag Berlin Heidelberg
%R doi:10.1007/s11600-018-0215-1
%L epos2208