Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable

Huang, Yihe; Ellsworth, William L.; Beroza, Gregory C.

doi:10.1126/sciadv.1700772

Cited by 113 publications

(104 citation statements)

References 50 publications

(69 reference statements)

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“…On the other hand, Huang et al () find that natural and human‐induced seismicity with similar faulting mechanisms and at similar depths display comparable stress drops, indicating that both induced and natural events are driven by the in situ tectonic stress field and likely comparable rock deformation mechanisms. They also find indications of stress drops increasing with depth, which would imply that the coefficient α 3 in equation increases with depth as well.…”

Section: Interpretation and Wider Implicationsmentioning

confidence: 99%

Insights From Micromechanical Modeling of Intact Rock Failure: Event Characteristics, Stress Drops, and Force Networks

Baan

Chorney

2019

JGR Solid Earth

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We use a bonded‐particle method to investigate event characteristics, b values, internal force distributions, and stress drops in triaxial deformation tests. We simulate brittle through ductile deformation regimes. We find the following: (1) Event rates are proportional to anelastic axial strain: (i) significant and accelerating events rates only occur near peak stress (brittle deformation); (ii) event rates gradually increase until the anelastic strain plateaus (ductile deformation). (2) b value patterns show a systematic decrease when approaching peak stress, after which (i) they increase again (brittle case) or (ii) reach a constant minimum (ductile case). A decrease in b values is indicative of progressive internal damage, with an increasing event rate. (3) Weak‐ and strong‐force networks exist within the sample. Macrofailure of the sample occurs due to collapse of the strong‐force network. Acoustic emissions predominantly occur (i) within the weak‐force network allowing for tensile crack opening and closing despite the large compressive external stresses, and (ii) in areas with the largest spatial force gradients, close to the strong‐force networks. All internal compressive and extensional normal forces display exponential distributions despite uniform boundary stresses. (4) Stress drops of the largest events are inversely proportional to peak stress; the largest stress drops occur for brittle failure, progressively approaching a zero magnitude for ductile deformation. The systemic correlations between b values, the number of acoustic emissions, and stress drops with the maximum principal stress may offer opportunities to invert for changes in the stress state from these remote observables during earthquake cycles.

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Section: Interpretation and Wider Implicationsmentioning

confidence: 99%

Insights From Micromechanical Modeling of Intact Rock Failure: Event Characteristics, Stress Drops, and Force Networks

Baan

Chorney

2019

JGR Solid Earth

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“…It is reported that stress drops recorded as a result of induced seismic events are of the same order of magnitude as those resulting from tectonic seismicity. Thus, the theoretical underpinnings for understanding tectonic earthquakes can be uniformly applied to induced earthquakes (Huang et al, ). On the basis of Brune's source model (Brune, ) and circular crack model (Vouillamoz et al, ), the relationship between seismic moment M 0 and stress drop Δ τ can be expressed as

M_{0} = \frac{16}{7} ∆ τ \cdot r^{3}

where r is the fault radius and Δ τ is the stress drop and can be calculated from RSF theory as

∆ τ = ∆ μ \cdot σ_{n}

∆ μ = (||, a - b) ln ((), \frac{V_{2}}{V_{1}})

where Δ μ is the difference in the friction coefficient from before until after the stress drop.…”

Section: Discussionmentioning

confidence: 99%

The Role of Mineral Composition on the Frictional and Stability Properties of Powdered Reservoir Rocks

Zhang

et al. 2019

JGR Solid Earth

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The growing hazard of induced seismicity driven by the boom in unconventional resources exploitation is strongly linked to fault activation. We perform laboratory measurements on simulated fault gouges comprising powdered reservoir rocks from major oil and gas production sites in China, to probe the control of mineral composition on fault friction and stability responses during reservoir stimulation. Double direct shear experiments were conducted on gouges with phyllosilicate content ranging from 0 to 30 wt.% and grain sizes <150 μm, at constant normal stresses of 10–40 MPa and conditions of room temperature and water saturation. The velocity step and slide‐hold‐slide sequences were employed to evaluate frictional stability and static healing, respectively. Results indicate that the mineralogy of the gouges exhibit a strong control on the frictional strength, stability, and healing. Phyllosilicate‐rich samples show lower frictional strength μ and higher values of (a − b), promoting stable sliding. For the gouges studied, the frictional strength decreases monotonically with increasing phyllosilicate content, and a transition from velocity weakening to velocity strengthening behavior is evident at 15 wt.% phyllosilicates. Intermediate healing rates are common in gouges with higher content of phyllosilicates, with high healing rates predominantly in phyllosilicate‐poor gouges. As an indispensable component in reservoir rocks, the carbonates are shown to affect both the frictional stability and healing response. These findings can have important implications for understanding the effects of mineralogy on fault behavior and induced seismic potential in geoengineering activities, particularly in reservoirs in China.

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“…We focus on the S waves as the P wave window is too short to obtain stable spectral ratio results. We find the best fit spectral ratio to the Brune source model (Imanishi & Ellsworth, ), that is, smallest misfit between the observed spectral ratio and the modeled spectral ratio, using the trust‐region‐reflective‐optimization approach (Huang et al, ). This approach minimizes a function f ( x ) by approximating it using a simpler function q around the point x in a neighborhood N (Moré & Sorensen, ).…”

Section: Spectral Ratio Analysis Of Microseismic Sourcesmentioning

confidence: 99%

“…Fluid pressure is usually considered as the major driving force in the generation of induced earthquakes when injection wells are close to the fault (Raleigh et al, ), whereas stress loading due to poroelastic deformation can take over when injection wells are more distant (Goebel & Brodsky, ; Segall & Lu, ). Geomechanical models show that the current injection wells in Oklahoma (USA) can induce fluid pressure and stress loading of the order of 0.1 MPa (Keranen et al, ), which is much smaller than the stress drop estimates of moderate‐magnitude‐induced earthquakes that have a median stress drop of about 1–20 MPa (Boyd et al, ; Huang et al, ; Trugman et al, ; Wu et al, ). The small ratio of fluid pressure perturbation and earthquake stress drop suggests that faults are almost critical before injection takes place (Townend & Zoback, ) and even a small fluid pressure or stress perturbation can make the faults reach favorable conditions for earthquake nucleation.…”

Section: Introductionmentioning

confidence: 99%

Illuminating the Rupturing of Microseismic Sources in an Injection‐Induced Earthquake Experiment

Huang

Barros

Cappa

2019

Geophysical Research Letters

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We analyze source parameters of Mw −3.9 to −3.1 induced earthquakes during an in situ fluid injection experiment in France using the spectral ratio method based on empirical Green's function. We choose 10 event pairs with highly similar waveforms and resolve their spectral ratios using multiple S wave windows. We find that master events ruptured meter‐scale source patches with <1‐μm slip in a preexisting fracture network oriented differently from the injected plane. The temporal correlation between master earthquake occurrence and injection pressure peak and the relatively low ratio of stress drop to crustal strength suggest that both fluid pressure perturbation and aseismic deformation play important roles in inducing the earthquakes. The comparison between stress drops of induced earthquakes in the experiment and in the central United States indicates a dependency of stress drop on crustal shear strength.

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Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable

Abstract: Induced earthquakes have comparable stress drop and ground motion to natural earthquakes given similar depths and faulting styles.

Cited by 113 publications

References 50 publications

Insights From Micromechanical Modeling of Intact Rock Failure: Event Characteristics, Stress Drops, and Force Networks

Insights From Micromechanical Modeling of Intact Rock Failure: Event Characteristics, Stress Drops, and Force Networks

The Role of Mineral Composition on the Frictional and Stability Properties of Powdered Reservoir Rocks

Illuminating the Rupturing of Microseismic Sources in an Injection‐Induced Earthquake Experiment

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