Stress inversion of shear-tensile focal mechanisms with application to hydraulic fracture monitoring

Jia, Suzie Qing; Eaton, David W.; Wong, R.C.K.

doi:10.1093/gji/ggy290

Cited by 23 publications

(13 citation statements)

References 48 publications

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“…However, as reported by Jia et al. (2018), the differences between both the inversions are small for events with slope angles | α | less than 30°. Since the slope angle | α | is less than 15° in our target area, applying the standard stress inversion of the DC focal mechanisms is fully satisfactory.…”

Section: Introductionsupporting

confidence: 67%

Mapping Stress and Fluids on Faults by Nonshear Earthquakes

et al. 2021

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Knowledge of tectonic stress, fault geometry, rheological properties of rocks and presence of fluids in the focal zone is essential for understanding earthquakes and their sequences in seismically active regions. Faults are complex systems with subfaults or fault segments of various lengths and shapes, which mutually intersect or form fault step overs (Fossen & Rotevatn, 2016; Micklethwaite et al., 2015). Fault irregularities, fault steps and fault tips become stress concentrators and interact under the stress field (Crider & Pollard, 1998; Lin & Stein, 2004; Madden et al., 2013) producing damage zones (Kim et al., 2004), and a large variety of seismic energy release such as background and clustered seismicity including foreshocks, mainshock-aftershocks or earthquake swarms (Mogi, 1963). Tectonic stress and fluids also control creation or reactivation of faults and their fracturing mode (Sibson, 1992; Vavryčuk & Hrubcová, 2017). A detailed geometric description of complex fracturing is provided by seismic moment tensors (MTs), which characterize rupturing mode on all scales: from acoustic emissions to large-size earthquakes. The MTs consist of double-couple (DC) components, representing shear focal mechanisms, and nondouble-couple (nonDC) components. According to the commonly used decomposition, the nonDC components consist of isotropic (ISO) and compensated linear vector dipole (CLVD) components (Jost & Hermann, 1989; Julian et al., 1998; Knopoff & Randall, 1970). The DC components are prevailing, but the nonDC components are also frequently detected. The nonDC components are produced, for example, by a collapse of cavities in mines (

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Section: Introductionsupporting

confidence: 67%

Mapping Stress and Fluids on Faults by Nonshear Earthquakes

et al. 2021

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“…In this study, the moment tensors were utilized to conduct formal stress inversions, and reduced stress tensors consisting of only four components (three principal stress orientations and their relative magnitudes) can be calculated (Vavryčuk, 2014). Two stress inversion methods were used: the original STRESSINVERSE MATLAB code developed by Vavrycuk ( 2014), and the STESI code developed by Jia et al (2018b).…”

Section: Stress Inversionmentioning

confidence: 99%

Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging

Jia

Wong

Eaton

2021

Geophysical Journal International

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Summary Crack nucleation and rock failure processes in a fine-grained siltstone (Montney Formation) under triaxial compression are investigated using combined diagnostic techniques, including ultrasonic-wave measurement, acoustic-emission (AE) monitoring, computed tomography (CT) scanning, and thin-section imaging. The sample displays a weak-to-moderate inherent seismic anisotropy and noticeable stress-induced anisotropy prior to failure. No AE event was detected until the applied axial stress reached 95 per cent of the peak value. The signal-to-noise ratio is relatively low, however, and detectable AE events are more diffuse than those observed in highly brittle rocks. The AE locations correlate with a shear fracture zone imaged by CT scanning. AE moment-tensor analysis reveals that events with larger relative magnitudes are characterized by high volumetric (tensile or compressive) components, and the initiation of the failure zone is dominated by combined shear-tensile failure. Stress inversion of the AE events with high tensile components is in good agreement with the known applied stress. Microscopic imaging of thin sections from the failed sample shows that the failure zone is an en echelon structure consisting of a major fracture with branching micro and minor cracks. This failure mechanism is consistent with a shear-tensile source mechanism and is interpreted to be associated with the fine granular structure and mineral composition of Montney siltstone.

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“…Numerical modelling studies of the deformation around voids and cracks might usefully incorporate a wider range of values of E and ν. Visualisation of direction-specific elastic properties will be useful for future investigations of the mechanics of twinning, dislocations, and fractures in a wide range of minerals. Earthquake focal mechanisms are known to depend on the elastic anisotropy of the source region (Vavryčuk, 2005), and better understanding of the anisotropies in rock-forming minerals is informing models of fabrics in subducting slabs (Li et al, 2018) and interpretations of microseismicity from commercial hydraulic fracturing operations (Jia et al, 2018). A practical assessment of the contribution of elastic strain energy to metamorphic reactions might involve the systematic mapping of major element chemistry around specific inclusions.…”

Section: Further Workmentioning

confidence: 99%

The variation and visualisation of elastic anisotropy in rock-forming minerals

2020

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Abstract. All minerals behave elastically; elasticity is a rheological property that controls their ability to support stress, strain, and pressure; controls the nature of acoustic wave propagation; and influences subsequent plastic (i.e. permanent non-reversible) deformation. All minerals are intrinsically anisotropic in their elastic properties – that is, they have directional variations that are related to the configuration of the crystal lattice. This means that the commonly used mechanical elastic properties that relate elastic stress to elastic strain, including Young's modulus (E), Poisson's ratio (ν), shear modulus (G) and linear compressibility (β), are dependent on crystallographic direction. In this paper, we explore the ranges of anisotropy of E, ν, G and β in 86 rock-forming minerals, using previously published data, and show that the range is much wider than commonly assumed. We also explore how these variations (the directionality and the magnitude) are important for fundamental processes in the solid earth, including deformation (mechanical) twinning, coherent phase transformations and brittle failure. We present a new open-source software package (AnisoVis, written in MATLAB), which we use to calculate and visualise directional variations in elastic properties of rock-forming minerals. Following previous work in the fields of chemistry and materials science, we demonstrate that by visualising the variations in elasticity, we discover previously unreported properties of rock-forming minerals. For example, we show previously unreported directions of negative Poisson's ratio and negative linear compressibility, and we show that the existence of these features is more widespread (i.e. present in many more minerals) than previously thought. We illustrate the consequences of intrinsic elastic anisotropy for the elastic normal and shear strains within α-quartz single crystal under different applied stress fields; the role of elastic anisotropy on Dauphiné twinning and the α–β phase transformations in quartz; and stress distributions around voids of different shapes in talc, lizardite, albite, and sanidine. In addition to our specific examples, elastic anisotropy in rock-forming minerals, to the degree that we describe, has significant consequences for seismic (acoustic) anisotropy, for the focal mechanisms of earthquakes in anisotropic source regions (e.g. subducting slabs), for a range of brittle and ductile deformation mechanisms in minerals, and for geobarometry using mineral inclusions.

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Stress inversion of shear-tensile focal mechanisms with application to hydraulic fracture monitoring

Cited by 23 publications

References 48 publications

Mapping Stress and Fluids on Faults by Nonshear Earthquakes

Mapping Stress and Fluids on Faults by Nonshear Earthquakes

Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging

The variation and visualisation of elastic anisotropy in rock-forming minerals

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