eprintid: 1685 rev_number: 16 eprint_status: archive userid: 2 dir: disk0/00/00/16/85 datestamp: 2016-05-30 13:53:36 lastmod: 2017-05-16 12:36:22 status_changed: 2016-05-30 13:53:36 type: article metadata_visibility: show creators_name: Martinez-Garzon, Patricia creators_name: Kwiatek, Grzegorz creators_name: Sone, Hiroki creators_name: Bohnhoff, Marco creators_name: Dresen, Georg creators_name: Hartline, Craig creators_id: creators_id: kwiatek@gfz-potsdam.de creators_id: creators_id: bohnhoff@gfz-potsdam.de creators_id: dre@gfz-potsdam.de creators_id: corp_creators: Helmholtz-Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany corp_creators: Helmholtz-Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany corp_creators: Helmholtz-Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany corp_creators: Helmholtz-Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, Institute of Geological Sciences, Free University Berlin, Berlin, Germany corp_creators: Helmholtz-Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, 3Institute of Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany corp_creators: Calpine Corporation, Middletown, California, USA title: Spatiotemporal changes, faulting regimes, and source parameters of induced seismicity: A case study from The Geysers geothermal field subjects: MP1 subjects: MP2 subjects: MP4 subjects: RU1_1 subjects: SG divisions: IP13 full_text_status: none abstract: The spatiotemporal, kinematic, and source characteristics of induced seismicity occurring at different fluid injection rates are investigated to determine the predominant physical mechanisms responsible for induced seismicity at the northwestern part of The Geysers geothermal field, California. We analyze a relocated hypocenter catalog from a seismicity cluster where significant variations of the stress tensor orientation were previously observed to correlate with injection rates. We find that these stress tensor orientation changes may be related to increased pore pressure and the corresponding changes in poroelastic stresses at reservoir depth. Seismic events during peak injections tend to occur at greater distances from the injection well, preferentially trending parallel to themaximum 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. date: 2014-11 date_type: published publication: Journal of Geophysical Research: Solid Earth volume: 119 number: 11 publisher: John Wiley & Sons pagerange: 8378-8396 id_number: doi:10.1002/2014JB011385 issn: 2169-9313 official_url: http://doi.org/10.1002/2014JB011385 access_IS-EPOS: limited owner: Publisher citation: Martinez-Garzon, Patricia and Kwiatek, Grzegorz and Sone, Hiroki and Bohnhoff, Marco and Dresen, Georg and Hartline, Craig (2014) Spatiotemporal changes, faulting regimes, and source parameters of induced seismicity: A case study from The Geysers geothermal field. Journal of Geophysical Research: Solid Earth, 119 (11). pp. 8378-8396. DOI: https://doi.org/10.1002/2014JB011385