Spatiotemporal changes, faulting regimes and source-parameters of induced seismicity: A case study from The Geysers geothermal field

Martínez-Garzón, P., G. Kwiatek, H. Sone, M. Bohnhoff, G. Dresen, and C. Hartline (2014). Spatiotemporal changes, faulting regimes and source-parameters of induced seismicity: A case study from The Geysers geothermal field, J. Geophys. Res. 119, DOI: 10.1002/2014JB011385. [ Article page ]

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We investigate short-term spatiotemporal, kinematic, and source characteristics of induced seismicity occurring at the northwestern part of The Geysers geothermal field, California, in response to different fluid injection rates. Seismic events during peak injections tend to occur at greater distances from the injection well, preferentially trending parallel to the maximum horizontal stress direction. In contrast, at lower injection rates the seismicity tends to align in a different direction which suggests the presence of a local fault. During peak injection intervals, the relative contribution of strike-slip faulting mechanisms increases. Furthermore, increases in fluid injection rates also coincide with a decrease in b-values. Our observations suggest that regardless of the injection stage, most of the induced seismicity results from thermal fracturing of the reservoir rock. However, during peak injection intervals, the increase in pore pressure may likewise be responsible for the induced seismicity. By estimating the thermal and hydraulic diffusivities of the reservoir, we confirm that the characteristic diffusion length for pore pressure is much greater than the corresponding length scale for temperature and also more consistent with the spatial extent of seismicity observed during different injection rates.
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  • 13 November 2018 Create Date
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