TY  - JOUR
ID  - epos2084
UR  - http://doi.org/10.1002/2017JB014473
IS  - 9
A1  - Diehl, Tobias
A1  - Kraft, Toni
A1  - Kissling, Edi
A1  - Wiemer, Stefan
N2  - In July 2013, a sequence of more than 340 earthquakes was induced by reservoir stimulations and well?control procedures following a gas kick at a deep geothermal drilling project close to the city of St. Gallen, Switzerland. The sequence culminated in an ML 3.5 earthquake, which was felt within 10?15 km from the epicenter. High?quality earthquake locations and 3?D reflection seismic data acquired in the St. Gallen project provide a unique data set, which allows high?resolution studies of earthquake triggering related to the injection of fluids into macroscopic fault zones. In this study, we present a high?precision earthquake catalog of the induced sequence. Absolute locations are constrained by a coupled hypocenter?velocity inversion, and subsequent double?difference relocations image the geometry of the ML 3.5 rupture and resolve the spatiotemporal evolution of seismicity. A joint interpretation of earthquake and seismic data shows that the majority of the seismicity occurred in the pre?Mesozoic basement, hundreds of meters below the borehole and the targeted Mesozoic sequence. We propose a hydraulic connectivity between the reactivated fault and the borehole, likely through faults mapped by seismic data. Despite the excellent quality of the seismic data, the association of seismicity with mapped faults remains ambiguous. In summary, our results document that the actual hydraulic properties of a fault system and hydraulic connections between its fault segments are complex and may not be predictable upfront. Incomplete knowledge of fault structures and stress heterogeneities within highly complex fault systems additionally challenge the degree of predictability of induced seismicity related to underground fluid injections.
VL  - 122
TI  - The induced earthquake sequence related to the St. Gallen deep geothermal project (Switzerland): Fault reactivation and fluid interactions imaged by microseismicity
AV  - none
EP  - 7290
N1  - Supporting Information
https://agupubs.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2F2017JB014473&attachmentId=2172498276
https://agupubs.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2F2017JB014473&attachmentId=2172498277
Y1  - 2017/08//
PB  - John Wiley & Sons
JF  - Journal of Geophysical Research: Solid Earth
SN  - 2169-9313
SP  - 7272
ER  -