The St. Gallen Fault Zone: a long-lived, multiphase structure in the North Alpine Foreland Basin revealed by 3D seismic data

Heuberger, Stefan; Roth, Philippe; Zingg, Olivier; Naef, H.; Meier, Beat

doi:10.1007/s00015-016-0208-5

Cited by 29 publications

(82 citation statements)

References 28 publications

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“…To find the optimal drilling target, a 3‐D seismic survey was conducted in 2010, in the area covering 270 km 2 . The survey revealed what was interpreted to be a pronounced fault zone, oriented NNE‐SSW with a length of about 30 km and a width of about 100 m [ Heuberger and Naef , ]. Heuberger and Naef [] concluded that the faults were ideally oriented in the stress field to be reactivated.…”

Section: The St Gallen Geothermal Projectmentioning

confidence: 99%

“…The survey revealed what was interpreted to be a pronounced fault zone, oriented NNE‐SSW with a length of about 30 km and a width of about 100 m [ Heuberger and Naef , ]. Heuberger and Naef [] concluded that the faults were ideally oriented in the stress field to be reactivated. Further, they suggested that this orientation indicated that the fault zone might exhibit an increased permeability.…”

Section: The St Gallen Geothermal Projectmentioning

confidence: 99%

“…This could explain the strength of the decoherence as well as its return to the initial values once the gas is back to its original formation and the possibly remaining gas concentration dispersed. Critically prestressed fault . The drilling targeted a fracture zone that extends several kilometers to the North and South and has a width of possibly 100 m [ Heuberger and Naef , ]. As indicated by Heuberger and Naef [] this fault zone is optimally oriented in the present‐day stress field.…”

Section: Interpretation and Conclusionmentioning

confidence: 99%

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Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland)

2015

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The failures of two recent deep geothermal energy projects in Switzerland (Basel, 2006; St. Gallen, 2013) have again highlighted that one of the key challenges for the successful development and operation of deep underground heat exchangers is to control the risk of inducing potentially hazardous seismic events. In St. Gallen, after an injection test and two acid injections that were accompanied by a small number of micro-earthquakes (M L < 0.2), operators were surprised by an uncontrolled gas release from the formation (gas kick). The "killing" procedures that had to be initiated following standard drilling procedures led to a M L 3.5 earthquake. With ambient seismic noise cross correlations from nine stations, we observe a significant loss of waveform coherence that we can horizontally and vertically constrain to the injection location of the fluid. The loss of waveform coherence starts with the onset of the fluid injections 4 days prior to the gas kick. We interpret the loss of coherence as a local perturbation of the medium. We show how ambient seismic noise analysis can be used to assess the aseismic response of the subsurface to geomechanical well operations and how this method could have helped to recognize the unexpected reservoir dynamics at an earlier stage than the microseismic response alone, allowed.

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Section: The St Gallen Geothermal Projectmentioning

confidence: 99%

Section: The St Gallen Geothermal Projectmentioning

confidence: 99%

Section: Interpretation and Conclusionmentioning

confidence: 99%

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Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland)

2015

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“…Heuberger et al 2016), or the Freiburg-BonndorfBodensee fault in the Hegau area (e.g. Egli et al 2016).…”

Section: Discussionmentioning

confidence: 99%

Multi-scale imaging of a slow active fault zone: contribution for improved seismic hazard assessment in the Swiss Alpine foreland

Vouillamoz

Mosar

Deichmann³

2017

Swiss J Geosci

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Seismic hazard assessment of slow active fault zones is challenging as usually only a few decades of sparse instrumental seismic monitoring is available to characterize seismic activity. Tectonic features linked to the observed seismicity can be mapped by seismic imaging techniques and/or geomorphological and structural evidences. In this study, we investigate a seismic lineament located in the Swiss Alpine foreland, which was discussed in previous work as being related to crustal structures carrying in size the potential of a magnitude M 6 earthquake. New, low-magnitude (-2.0 B M L B 2.5) earthquake data are used to image the spatial and temporal distribution of seismogenic features in the target area. Quantitative and qualitative analyses are applied to the waveform dataset to better constrain earthquakes distribution and source processes. Potential tectonic features responsible for the observed seismicity are modelled based on new reinterpretations of oil industry seismic profiles and recent field data in the study area. The earthquake and tectonic datasets are then integrated in a 3D model. Spatially, the seismicity correlates over 10-15 km with a N-S oriented sub-vertical fault zone imaged in seismic profiles in the Mesozoic cover units above a major decollement on top of the mechanically more rigid basement and seen in outcrops of Tertiary series east of the city of Fribourg. Observed earthquakes cluster at shallow depth (\4 km) in the sedimentary cover. Given the spatial extend of the observed seismicity, we infer the potential of a moderate size earthquake to be generated on the lineament. However, since the existence of along strike structures in the basement cannot be excluded, a maximum M 6 earthquake cannot be ruled out. Thus, the Fribourg Lineament constitutes a non-negligible source of seismic hazard in the Swiss Alpine foreland.

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“…The underlying Precambrian to Paleozoic crystalline basement of the Alpine foreland is in parts dissected by roughly SW‐NE striking Permo‐Carboniferous troughs (PCTs) [ McCann et al ., ; Naef and Madritsch , , and references therein], as verified by deep wells and reflection seismic data [e.g., Laubscher , ; Diebold et al ., ; Gorin et al ., ; Meier , ; Sommaruga et al ., ; Heuberger et al ., ]. They developed in consequence of the Late Carboniferous to Permian collapse of the Variscan orogen, as narrow basins in a wrench‐tectonic setting during an extensional to transtensional stress regime, disrupted by a phase of Early Permian transpression [ Diebold et al ., ; Marchant et al ., ; McCann et al ., , and references therein].…”

Section: Geological Settingmentioning

confidence: 99%

Tectonics of the central Swiss Molasse Basin: Post‐Miocene transition to incipient thick‐skinned tectonics?

Mock

Herwegh

2017

Tectonics

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In this paper we investigate the tectonics of the central Swiss Molasse Basin (SMB), situated between the central European Alps and the Jura fold‐and‐thrust belt. Based on (re)interpreted 2‐D reflection seismic data and geological 3‐D modeling, we present new insights into the structural configuration and evolution of the central SMB. During the thin‐skinned, main deformation phase of the Jura fold‐and‐thrust belt (~12–4 Ma), the central SMB was riding passively above a major detachment horizon within Triassic evaporites, which roots beneath the External Crystalline Massifs of the Central Alps. In the SMB, low‐amplitude detachment folds and detachment‐rooted WSW‐ENE striking thrust and reverse faults are related to this event. Younger, major NNE‐SSW and NNW‐SSE trending strike‐slip fault zones cross the basin over a length of several kilometers, affecting the Cenozoic and Mesozoic cover units and extending into the pre‐Mesozoic crystalline basement. In cases, the fault zones apparently reactivate inherited, Permo‐Carboniferous trough (PCT) bounding, Paleozoic normal faults. Seismic data further reveal mild inversion of WSW‐ENE striking PCTs. These structures clearly cut the basement‐cover contact, thus postdating the main deformation phase of the Jura fold‐and‐thrust belt. Present‐day earthquake focal mechanisms and epicenter distribution show strike‐slip faulting and basement‐seated seismicity, respectively, thus corroborating our observations from seismic interpretation. Our data suggest a change from late Miocene thin‐skinned to Pliocene to present‐day incipient thick‐skinned tectonics. This major change reflects the establishment of a midcrustal detachment and may be related to changes in slab dynamics of the subducting European lithosphere.

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The St. Gallen Fault Zone: a long-lived, multiphase structure in the North Alpine Foreland Basin revealed by 3D seismic data

Cited by 29 publications

References 28 publications

Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland)

Potential of ambient seismic noise techniques to monitor the St. Gallen geothermal site (Switzerland)

Multi-scale imaging of a slow active fault zone: contribution for improved seismic hazard assessment in the Swiss Alpine foreland

Tectonics of the central Swiss Molasse Basin: Post‐Miocene transition to incipient thick‐skinned tectonics?

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