Temporal response of magnitude distribution to fluid injection rates in The Geysers geothermal field

Leptokaropoulos, Konstantinos Michail and Staszek, Monika (2019) Temporal response of magnitude distribution to fluid injection rates in The Geysers geothermal field. Acta Geophysica, 67 (1). pp. 327-339. DOI: https://doi.org/10.1007/s11600-018-0215-1

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Official URL: http://doi.org/10.1007/s11600-018-0215-1


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.

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Item Type: Article
Uncontrolled Keywords: Injection-induced seismicity Magnitude distribution Geothermal fields Statistical seismology
Subjects: Methodology > Method and procesing > Collective properties of seismicity
Region > USA > California > Geysers
Inducing technology > Geothermal energy production
Project: SHEER project
EPOS-IP > THE GEYSERS Prati 9 and Prati 29 cluster: Treated wastewater injection for geothermal power production