ROLE OF FLUID INJECTION ON EARTHQUAKE SIZE IN DYNAMIC RUPTURE SIMULATIONS ON ROUGH FAULTS

Abstract. In a spirit akin to the sandpile model of self-organized criticality, we present a simple statistical model of the cellular-automaton type which simulates the role of an asperity in the dynamics of a one-dimensional fault. This model produces an earthquake spectrum similar to the characteristic-earthquake behaviour of some seismic faults. This model, that has no parameter, is amenable to an algebraic description as a Markov Chain. This possibility illuminates some important results, obtained by Monte Carlo simulations, such as the earthquake size-frequency relation and the recurrence time of the characteristic earthquake.

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Exploring Physical Links between Fluid Injection and Nearby Earthquakes: The 2012 Mw 4.8 Timpson, Texas, Case Study

Bulletin of the Seismological Society of America ◽

10.1785/0120200090 ◽

2020 ◽

Vol 110 (5) ◽

pp. 2350-2365 ◽

Cited By ~ 1

Author(s):

Dawid Szafranski ◽

Benchun Duan

Keyword(s):

Aftershock Sequence ◽

Fluid Injection ◽

Dynamic Rupture ◽

Predictive Tool ◽

Dynamic Friction Coefficient ◽

Effective Normal Stress ◽

A Value ◽

Dynamic Rupture Model ◽

Rupture Model

ABSTRACT In this work, we integrate a fluid-flow model of 3D deformable porous media with a dynamic rupture model of earthquakes in 3D heterogeneous geologic medium. The method allows us to go beyond fault failure potential analyses and to examine how big an earthquake can be if part of a fault reaches failure due to fluid injection. We apply the method to the 17 May 2012 Mw 4.8 Timpson, Texas, earthquake as a case study. The simulated perturbations of pore pressure and stress from wastewater injection at the time of the mainshock are high enough (several MPa) to trigger an earthquake. Dynamic rupture modeling could reproduce the major observations from the Mw 4.8 event, including its size, focal mechanism, and aftershock sequence, and thus building a more convincing physical link between fluid injection and the Mw 4.8 earthquake. Furthermore, parameter space studies of dynamic rupture modeling allow us to place some constraints on fault frictional properties and background stresses. For the Timpson case, we find that a dynamic friction coefficient of ∼0.3, a value of ∼0.1 m for the critical slip distance in the slip-weakening friction law, and uniform effective normal stress are associated with the Timpson earthquake fault. By reproducing main features of the aftershock sequence of the mainshock, we also demonstrate that the method has potential to become a predictive tool for fluid injection design in the future.

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On the role of stress waves in dynamic rupture of cylindrical tubes

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/ffe.12621 ◽

2017 ◽

Vol 40 (12) ◽

pp. 2008-2018 ◽

Cited By ~ 5

Author(s):

M. Mirzaei ◽

S. Tavakoli ◽

M. Najafi

Keyword(s):

Stress Waves ◽

Dynamic Rupture ◽

Cylindrical Tubes

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From arteries to boreholes: transient response of a poroelastic cylinder to fluid injection

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2018.0284 ◽

2018 ◽

Vol 474 (2216) ◽

pp. 20180284 ◽

Cited By ~ 1

Author(s):

L. C. Auton ◽

C. W. MacMinn

Keyword(s):

Transient Response ◽

Large Deformations ◽

Fluid Pressure ◽

Soft Materials ◽

Fluid Injection ◽

Solid Skeleton ◽

Fluid Flux ◽

Vascular Walls ◽

Initial Geometry

The radially outward flow of fluid through a porous medium occurs in many practical problems, from transport across vascular walls to the pressurization of boreholes in the subsurface. When the driving pressure is non-negligible relative to the stiffness of the solid structure, the poromechanical coupling between the fluid and the solid can control both the steady state and the transient mechanics of the system. Very large pressures or very soft materials lead to large deformations of the solid skeleton, which introduce kinematic and constitutive nonlinearity that can have a non-trivial impact on these mechanics. Here, we study the transient response of a poroelastic cylinder to sudden fluid injection. We consider the impacts of kinematic and constitutive nonlinearity, both separately and in combination, and we highlight the central role of driving method in the evolution of the response. We show that the various facets of nonlinearity may either accelerate or decelerate the transient response relative to linear poroelasticity, depending on the boundary conditions and the initial geometry, and that an imposed fluid pressure leads to a much faster response than an imposed fluid flux.

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Induced seismicity associated with fluid injection into a fractured rock mass

10.5194/egusphere-egu2020-13568 ◽

2020 ◽

Author(s):

Brice Lecampion ◽

Federico Ciardo ◽

Alexis Saèz Uribe ◽

Andreas Möri

Keyword(s):

Rock Mass ◽

Percolation Threshold ◽

Pore Pressure ◽

Finite Volume ◽

Fractured Rock ◽

Fluid Injection ◽

Aseismic Slip ◽

Dynamic Rupture ◽

Fractured Rock Mass

We investigate via numerical modeling the growth of an aseismic rupture and the possible nucleation of a dynamic rupture driven by fluid injection into a fractured rock mass. We restrict to the case of highly transmissive fractures compared to the rock matrix at the scale of the injection duration and thus assume an impermeable matrix. We present a new 2D hydro-mechanical solver allowing to treat a large number of pre-existing frictional discontinuities. The quasi-static (or quasi-dynamic) balance of momentum is discretized using boundary elements while fluid flow inside the fracture is discretized via finite volume. A fully implicit scheme is used for time integration. Combining a hierarchical matrix approximation of the original boundary element matrix with a specifically developed block pre-conditioner enable a robust and efficient solution of large problems (with up to 106 unknowns). In order to treat accurately fractures intersections, we use piece-wise linear displacement discontinuities element for elasticity and a vertex centered finite volume method for flow.We first consider the case of a randomly oriented discrete fracture network (DFN) having friction neutral properties. We discuss the very different behavior associated with marginally pressurized versus critically stressed conditions. As an extension of the case of a planar fault (Bhattacharya and Viesca, Science, 2019), the injection into a DFN problem is governed by the distribution (directly associated with fracture orientation) of a dimensionless parameter combining the local stress criticality (function of the in-situ principal effective stress, friction coefficient and local fracture orientation) and the normalized injection over-pressure. The percolation threshold of the DFN which characterizes the hydraulic connectivity of the network plays an additional role in fluid driven shear cracks growth. Our numerical simulations show that a critically stressed DFN exhibits fast aseismic slip growth (much faster than the fluid pore-pressure disturbance front propagation) regardless of the DFN percolation threshold. This is because the slipping patch growth is driven by the cascades of shear activation due to stress interactions as fractures get activated. On the other hand, the scenario is different for marginally pressurized / weakly critically stressed DFN. The aseismic slip propagation is then tracking pore pressure diffusion inside the DFN. As a result, the DFN percolation threshold plays an important role with low percolation leading to fluid localization and thus restricted aseismic rupture growth.We then discuss the case of fluid injection into a fault damage zone. Using a linear frictional weakening model for the fault, we investigate the scenario of the nucleation of a dynamic rupture occurring after the end of the injection (as observed in several instances in the field). We delimit the injection and in-situ conditions supporting such a possibility.

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

Bulletin of the Seismological Society of America ◽

10.1785/0120200106 ◽

2020 ◽

Vol 110 (5) ◽

pp. 2328-2349

Author(s):

Kadek Hendrawan Palgunadi ◽

Alice-Agnes Gabriel ◽

Thomas Ulrich ◽

José Ángel López-Comino ◽

Paul Martin Mai

Keyword(s):

Fault Plane ◽

Fluid Pressure ◽

Local Stress ◽

Stress Conditions ◽

Fluid Injection ◽

Geothermal System ◽

Dynamic Rupture ◽

Fault Interaction ◽

Induced Earthquake ◽

Secondary Fault

ABSTRACT 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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