Evidence for tensile faulting deduced from full waveform moment tensor inversion during the stimulation of the Basel enhanced geothermal system

Zhao, Peng; Kühn, Daniela; Oye, Volker; Cesca, Simone

doi:10.1016/j.geothermics.2014.01.003

Cited by 35 publications

(35 citation statements)

References 20 publications

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“…In particular, as shown in Figure 6, the ISO component can be as large as 40% (e.g., the event 2 on 13 July 2014). Previous studies demonstrate that during the stimulation process, induced events with higher ISO component typically occur close to the injection wells due to the complicated stress conditions [Zhao et al, 2014;Aker et al, 2014]. However, in those studies, because of limited data sources about the injection wells, the relationship between ISO component within the moment tensor and the epicentral distance with respect to the wellhead is not discussed in detail and the higher ISO components are also closely related to the damage and dilation zones around a single or multiple faults.…”

Section: 1002/2015jb012603mentioning

confidence: 99%

Discriminating induced seismicity from natural earthquakes using moment tensors and source spectra

et al. 2016

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Earthquake source mechanisms and spectra can provide important clues to aid in discriminating between natural and induced events. In this study, we calculate moment tensors and stress drop values for eight recent induced earthquakes in the Western Canadian Sedimentary Basin with magnitudes between 3.2 and 4.4, as well as a nearby magnitude 5.3 event that is interpreted as a natural earthquake. We calculate full moment tensor solutions by performing a waveform‐fitting procedure based on a 1‐D transversely isotropic velocity model. In addition to a dominant double‐couple (DC) signature that is common to nearly all events, most induced events exhibit significant non‐double‐couple components. A parameter sensitivity analysis indicates that spurious non‐DC components are negligible if the signal to noise ratio (SNR) exceeds 10 and if the 1‐D model differs from the true velocity structure by less than 5%. Estimated focal depths of induced events are significantly shallower than the typical range of focal depths for intraplate earthquakes in the Canadian Shield. Stress drops of the eight induced events were estimated using a generalized spectral‐fitting method and fall within the typical range of 2 to 90 MPa for tectonic earthquakes. Elastic moduli changes due to the brittle damage production at the source, presence of multiple intersecting fractures, dilatant jogs created at the overlapping areas of multiple fractures, or non‐planar pre‐existing faults may explain the non‐DC components for induced events.

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Section: 1002/2015jb012603mentioning

confidence: 99%

Discriminating induced seismicity from natural earthquakes using moment tensors and source spectra

et al. 2016

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“…The non-DC components reflect fault or fracture growth due to possible volume changes associated with fluid injection/extraction. While a few recent studies (e.g., Cesca et al, 2013;Zhang et al, 2016;Zhao et al, 2014) quantified the amount of non-DC components of induced events, characterizing and virtualizing non-DC components, especially those pertaining to fluid-injection induced earthquakes at the regional scale, remains a work in progress. contributions to fluid-induced events (e.g., Zhang et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Faults and Non‐Double‐Couple Components for Induced Earthquakes

Wang

Schultz

et al. 2018

Geophysical Research Letters

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Focal mechanisms of induced earthquakes reflect anthropogenic contributions to preexisting geological features and fault slippages. In this paper, we examine fault‐related (double‐couple (DC)) and possibly fluid‐related (non‐double‐couple (non‐DC)) mechanisms of induced earthquakes (M2–6) at regional scales. We systematically compare well‐resolved focal mechanisms of 33 events in the Western Canada Sedimentary Basin, among which 12 were induced by hydraulic fracturing and one by secondary recovery. Most of the seismicity is dominated by strike‐slip/thrust faulting regimes, whereas limited (but consistent) non‐DC components are obtained from injection‐induced seismicity in central Alberta. We interpret the persistent compensated‐linear‐vector‐dipole components (M2.1–3.8) as reflecting fracture growth and/or noncoplanar faults slippages during hydraulic‐fracturing stimulations. We further expand the moment tensor decomposition analysis to four representative classes of induced seismicity globally and find that the overall contribution of non‐DC components is comparable between induced and tectonic earthquakes.

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“…Although in some cases, no evidence for tensile source radiation patterns was found (Nolen-Hoeksema & Ruff, 2001;Phillips, Fairbanks, Rutledge, & Anderson, 1998;Warpinski, 1997), later studies identified significant non-DC terms for hydrofracture events (Jechumt alov a & Eisner 2008; Sileny et al, 2009;Warpinski & Du, 2010). Similar non-DC source models have also been proposed for induced seismicity in geothermal environments (Zhao, K€ uhn, Oye, & Cesca, 2014). Hasegawa, Wetmiller, and Gendzwill (1989) discussed six possible failure mechanisms accompanying mining activities.…”

Section: The Microseismic Sourcementioning

confidence: 85%