The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

Lim, Hobin; Deng, Kai; Kim, Yeo Hyung; Ree, Jin-Han; Song, Tae Bok; Kim, K.‐H.

doi:10.1029/2019jb019134

Cited by 36 publications

(23 citation statements)

References 44 publications

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“…While pore pressure dominates in magnitude and promotes failure by reducing effective normal stress, shear stress changes can affect the regimes on a preexisting fault where shear slip is promoted or inhibited, and hence, locations of larger positive Δ CFS where earthquakes are more likely triggered. A similar relationship between earthquake location and positive shear stress change is observed for the 2017 Pohang earthquake (Lim et al, 2020). Numerical studies on seismicity rate related to fluid injection also suggest that shear stress can increase or decrease seismicity, depending on the geometry of the faults relative to the injection source (Chang & Segall, 2016; Segall & Lu, 2015).…”

Section: Discussionsupporting

confidence: 71%

Correlation Between Poroelastic Stress Perturbation and Multidisposal Wells Induced Earthquake Sequence in Cushing, Oklahoma

Deng

Liu

Chen

2020

Geophysical Research Letters

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Over 100 small-to moderate-sized earthquakes, including an Mw 5.0 event, were detected during September 2015 to November 2016 near the town of Cushing, Oklahoma. The seismic sequence was spatial-temporally linked to four wastewater disposal wells within 4 km. We calculate pore pressure and stress perturbations caused by fluid injection at multiple wells and analyze seismic risk in a Coulomb failure stress framework. Despite being more than an order of magnitude smaller than the pore pressure perturbation, the sign of shear stress change, in the sense of assumed right-lateral fault motion, dictates where earthquakes are induced. Most of the relocated earthquakes are located within areas of positive shear stress changes. Our results suggest that poroelastic stress changes also play an essential role in the wastewater disposal environment, and a strategic design of well locations with respect to fault orientation and direction of motion can help mitigate induced seismic hazard. Plain Language Summary Fluid injected into the subsurface is known to induce earthquakes. This study analyzes the relationship between the 2015/2016 Cushing earthquake sequence and wastewater disposal at four wells within 4 km of the sequence. Our results reveal that while pore pressure increase due to fluid diffusion makes the dominant contribution to promote fault slip toward instability, shear stress change in the sense of motion on a preexisting fault is a critical factor that determines where earthquakes can occur. This study suggests that a strategic design of disposal wells locations, with respect to mapped faults, may be an effective way to mitigate injection-induced seismicity.

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Section: Discussionsupporting

confidence: 71%

Correlation Between Poroelastic Stress Perturbation and Multidisposal Wells Induced Earthquake Sequence in Cushing, Oklahoma

Deng

Liu

Chen

2020

Geophysical Research Letters

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“…Pore pressure diffusion requires hydraulic connectivity between the injection aquifer and seismogenic fault. However, stress transmission can elevate the CFS and induce earthquakes despite insignificant fluid diffusion to hypocenters due to the large distance or low permeability (51). Our compilation and analysis of regional fluid injection and extraction in the Delaware Basin permit a better understanding of the physical mechanism and mechanical control on induced seismicity (Fig.…”

Section: Discussionmentioning

confidence: 99%

Widespread deep seismicity in the Delaware Basin, Texas, is mainly driven by shallow wastewater injection

Zhai

Shirzaei

Manga

2021

Proc. Natl. Acad. Sci. U.S.A.

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Industrial activity away from plate boundaries can induce earthquakes and has evolved into a global issue. Much of the induced seismicity in the United States' midcontinent is attributed to a direct pressure increase from deep wastewater disposal. This mechanism is not applicable where deep basement faults are hydraulically isolated from shallow injection aquifers, leading to a debate about the mechanisms for induced seismicity. Here, we compile industrial, seismic, geodetic, and geological data within the Delaware Basin, western Texas, and calculate stress and pressure changes at seismogenic depth using a coupled poroelastic model. We show that the widespread deep seismicity is mainly driven by shallow wastewater injection through the transmission of poroelastic stresses assuming that unfractured shales are hydraulic barriers over decadal time scales. A zone of seismic quiescence to the north, where injection-induced stress changes would promote seismicity, suggests a regional tectonic control on the occurrence of induced earthquakes. Comparing the poroelastic responses from injection and extraction operations, we find that the basement stress is most sensitive to shallow reservoir hydrogeological parameters, particularly hydraulic diffusivity. These results demonstrate that intraplate seismicity can be caused by shallow human activities that poroelastically perturb stresses at hydraulically isolated seismogenic depths, with impacts on seismicity that are preconditioned by regional tectonics.

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“…Those changes may be related to elevated pore pressure and the corresponding changes in poroelastic stresses (Ceunot et al, 2006;Schoenball et al, 2014;Martínez-Garzón et al 2014;Jeanne et al, 2015). Lim et al (2020) Based on the analysis of our numerical experiments, we deduce that our models are highly sensitive to variations in the initial stress state, and therefore allow for finely constraining the fault stress loading parameters. For example, a small change in &'() may induce a significant change in the modeled focal mechanism.…”

Section: Model 2f Validation By Regional Waveform Modelingmentioning

confidence: 75%

Dynamic Fault Interaction during a Fluid-Injection-Induced Earthquake: The 2017 Mw 5.5 Pohang Event

Palgunadi

Gabriel

Ulrich

et al. 2020

Bulletin of the Seismological Society of America

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The 15 November 2017 Mw 5.5 Pohang, South Korea, earthquake has been linked to hydraulic stimulation and fluid injections, making it the largest induced seismic event associated with an enhanced geothermal system. To understand its source dynamics and fault interactions, we conduct the first 3D high-resolution spontaneous dynamic rupture simulations of an induced earthquake. We account for topography, off-fault plastic deformation under depth-dependent bulk cohesion, rapid velocity weakening friction, and 1D subsurface structure. A guided fault reconstruction approach that clusters spatiotemporal aftershock locations (including their uncertainties) is used to identify a main and a secondary fault plane that intersect under a shallow angle of 15°. Based on simple Mohr–Coulomb failure analysis and 180 dynamic rupture experiments in which we vary local stress loading conditions, fluid pressure, and relative fault strength, we identify a preferred two-fault-plane scenario that well reproduces observations. We find that the regional far-field tectonic stress regime promotes pure strike-slip faulting, whereas local stress conditions constrained by borehole logging generate the observed thrust-faulting component. Our preferred model is characterized by overpressurized pore fluids, nonoptimally oriented but dynamically weak faults and a close-to-critical local stress state. In our model, earthquake rupture “jumps” to the secondary fault by dynamic triggering, generating a measurable non-double-couple component. Our simulations suggest that complex dynamic fault interaction may occur during fluid-injection-induced earthquakes and that local stress perturbations dominate over regional stress conditions. Therefore, our findings have important implications for seismic hazard in active georeservoir.

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The 2017 Mw 5.5 Pohang Earthquake, South Korea, and Poroelastic Stress Changes Associated With Fluid Injection

Cited by 36 publications

References 44 publications

Correlation Between Poroelastic Stress Perturbation and Multidisposal Wells Induced Earthquake Sequence in Cushing, Oklahoma

Correlation Between Poroelastic Stress Perturbation and Multidisposal Wells Induced Earthquake Sequence in Cushing, Oklahoma

Widespread deep seismicity in the Delaware Basin, Texas, is mainly driven by shallow wastewater injection

Dynamic Fault Interaction during a Fluid-Injection-Induced Earthquake: The 2017 Mw 5.5 Pohang Event

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