Seismicity migration from fluid injection: Laboratory experiments and numerical models illuminate volume-driven versus pressure-diffusion-driven migration
Oct 2026· Earth and Planetary Science Letters· 0 citations· 71 references
Abstract
23 Fluid injection into the subsurface can induce seismicity by reactivating shear rupture, which 24 typically produces larger earthquake magnitudes than tensile rupture. In laboratory shear 25 rupture experiments, pressurization of the entire fault is often limited because large unconfined 26 samples allow fluid to leak at free surfaces. In this study, we investigated shear fault 27 reactivation by directly injecting fluid into a PMMA fault (760 mm long, 76 mm high) formed 28 as the interface between two separate PMMA blocks. To prevent leakage in the 76 mm 29 dimension, we made a low permeability barrier by coating the outer edges of the fault with 30 Teflon tape. Fluid pressure then extended along the 760 mm dimension, resulting in the 31 migration of seismicity away from the injection well. Changes in injection rate and fluid 32 viscosity revealed two mechanisms: (1) slow injection rate or low-viscosity fluid caused 33 seismicity migration governed by pressure diffusion, and (2) fast injection rate or high-34 viscosity fluid caused seismicity migration proportional to injected volume. Simulations with 35 a 2D poroelastic model showed that seismicity migrated with the fluid pressure front in the 36 volume-driven regime, whereas fluid pressure advanced well ahead of seismicity in the 37 pressure-diffusion-driven regime. These results highlight that Teflon tape effectively sealed 38 faults and controlled fluid flow, and that injection rate and fluid viscosity have a strong impact 39 on fault slip and induced seismicity. 40
Subsurface fluid injection, widely employed in enhanced geothermal systems, CO₂ geological storage, and unconventional hydrocarbon extraction, can reactivate pre‐existing faults and induce seismicity. We present a physics‐based numerical framework that integrates fluid pressure diffusion, poroelastic stressing, and rate‐and‐state friction to evaluate fault stability in homogeneous poroelastic reservoirs. Compared with traditional Coulomb failure stress (
CFS
) approaches, which rely on quasi‐static stress changes, the model captures a broad spectrum of slip behaviors, ranging from aseismic creep to dynamic rupture, and quantifies systematic controls exerted by injection rate, tectonic loading rate, fault orientation, and reservoir permeability. Our numerical simulations reveal that poroelastic stressing plays a dominant role in triggering fault slip, particularly at large distances from injection sources and during the early stage of injection. We demonstrate that elevated injection rates and tectonic loading rates produce similar effects on induced seismicity patterns. Favorably oriented faults experience early slip events that precede the arrival of the fluid pressure diffusion front, whereas unfavorably oriented faults exhibit delayed slip that occurs only after the pressure front passage. In low‐permeability formations, fault slip onset is delayed but characterized by higher slip velocities. We additionally examine the post‐injection (shut‐in) stage, during which pore pressure continues to accumulate before eventual dissipation. The results indicate that shut‐in can either mitigate or accelerate slip depending on fault orientation, stress regime, and pre‐shut‐in injection history. Importantly, once slip nucleation has initiated, shut‐in may fail to prevent induced seismicity, underscoring the critical importance of timing in operational mitigation.
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Qifeng Xie, Lei Wang, Qi Li· Deep Underground Science And...· 0 citations
Recent observations have revealed pore‐fluid pressure fluctuations correlated with the occurrence of slow slip events (SSEs) in several subduction zones. These fluctuations, caused by fluid accumulation and migration before and during SSEs, may modulate the timing and characteristics of these events. To test whether pore‐pressure changes can induce SSEs comparable to observations, we develop a physical model in which periodic changes in pore‐fluid pressure are imposed on a planar velocity‐weakening fault by varying the effective normal stress (one‐way coupling). Fluid is assumed to be injected at the center of the fault and to diffuse along the fault plane according to the axisymmetric diffusion equation. Our results show that these perturbations produce a spectrum of slip behaviors, from quasi‐periodic SSEs to earthquakes, including mixed behaviors. The induced SSEs have durations and magnitudes ranging from approximately 3 months to over a year and Mw ${\mathrm{M}}_{\mathrm{w}}$ 5.5–7.5. However, the model does not reproduce the full range of SSE properties observed in subduction zones, and the parameter space leading to SSEs is narrower than that of models with velocity‐strengthening faults. These findings support the previously proposed idea that SSEs are more consistently reproduced by models of velocity‐strengthening faults than by models of velocity‐weakening faults subjected to pore‐pressure perturbations.
Andrea Perez‐Silva, Y. Kaneko, Ting Wang· Geochemistry Geophysics Geos...· 0 citations
Fracture mechanics models suggest that aseismic slip may either lag behind or outpace the fluid pressure front, depending on injection conditions and the fault’s initial stress state. However, direct experimental validation of these predictions has been lacking. Here, we report laboratory experiments on granite samples under upper crustal stress conditions, where we simultaneously tracked the propagation of fluid pressure and aseismic slip during fluid injection. We show that aseismic slip lags the pressure front at low injection rates and low initial stress but rapidly outpaces it under high-rate injection or near-failure initial stress conditions. The transition is governed by a dimensionless loading parameter that integrates injection rate, fault strength, and initial shear stress. Our results provide direct support for fracture mechanics models of fluid-induced aseismic slip and suggest that in critically stressed crustal faults, rupture propagation may commonly outpace fluid diffusion.
F. Passelègue, N. Brantut, H. Chauris et al.· Science Advances· 0 citations
Elastic flexure of tectonic plates shapes large-scale topographic features and can induce notable slip on lithosphere-scale faults. At mid-ocean ridges, recent evidence shows that up to 50% of extensional fault offsets formed within axial valleys can be reversed by compressional slip across valley flanks. While standard models predict the location of this faulting, they consistently underpredict the depth-extent of compression and related surface offsets. Here, using numerical models, we show that elevated pore fluid pressures in compression allow increased slip on flexure-driven reverse faults. Quantitative agreement between modeled and observationally inferred reverse fault–bending strain is achieved only when pore-fluid pressures in reverse faults approach lithostatic levels. These findings highlight the critical role of inherited structural heterogeneities and high pore-fluid pressures in facilitating deep-seated reverse faulting during lithospheric unbending. This mechanism may also amplify flexure-induced seismicity in continental forebulges, such as the 2001 Bhuj earthquake (moment magnitude, 7.6), and underscores pore-pressure modulation as a fundamental control on global tectonic hazards.
Zhonglan Liu, W. R. Buck, J. Olive· Science Advances· 0 citations
In order to clarify the main controlling factors influencing fluid pressure changes in fault zones during the seismic cycle, we conducted laboratory rock friction experiments where fluid pressure was monitored in situ during sequences of quasi-static loading followed by dynamic slip events. The simulated fault was a 30$^\circ$ saw-cut in a Westerly granite cylinder, saturated with water, tested under triaxial conditions. Pore pressure was held constant at the boundaries of the block, but the low hydraulic diffusivity of Westerly granite made the fault hydraulically disconnected from the boundaries. During quasi-static loading while the fault was locked, we observed pore pressure increases which we interpret as poroelastic closure of the fault. During dynamic slip events, pore pressure systematically dropped by amplitudes commensurate to the normal stress drop. A large contribution to the pore pressure drop is interpreted as poroelastic opening of the fault. Deviations from the poroelastic effects are observed: in small events, pore pressure dropped further than anticipated, indicating inelastic dilation. In a few large events, pore pressure dropped less than anticipated, which could be the sign of compaction or thermal pressurisation. Prior to macroscopic slip events, we detect systematic pore pressure decreases by up to around 1 MPa, correlated to the occurrence of inhomogeneous preslip along the fault. Slip nucleation, inferred by kinematic inversion of local strain gauge data, is linked to local slip magnitudes of the order of 1 to 10 $\mu$m, and appears to lead to inelastic dilation. A stability analysis of fault slip including dilatant and poroelastic effects shows that poroelastic coupling tends to compensate normal stress variations, leading to faults operating under mostly constant effective normal stress if conditions are undrained.
N. Brantut, F. Passelegue, P. Dublanchet· Earth and Planetary Science...· 0 citations
During an earthquake a dynamic rupture propagates, causing fractures and permanent damage that modify the mechanical properties of the fault and its surroundings. Reciprocally, the energy dissipated by the mechanical transformation of the fault rock has a direct feedback on the dynamics of the seismic rupture. We reproduce and image these co‐seismic damage processes with sub‐microsecond time resolution through dynamic loading experiments on confined Westerly granite samples. Using synchrotron X‐ray imaging and ultra‐high‐speed cameras, we observed that dynamic compression with confinement produces shear faults and a localized granulation of the rock, known as gouge, before significant slip occurs. This fragmentation process begins with volumetric damage, followed by shear deformation less than 5 microseconds later. Our results indicate that gouge formation is initiated by the dynamic rupture itself, which reduces the strength of a fault prior to other weakening mechanisms that may occur during the earthquake slip.
A. Vishnu, M. Doan, J. Hollingsworth et al.· Geophysical Research Letters· 0 citations
A new method for surgically removing training examples from a model reveals that as datasets grow, the link between what a model learns and what it produces dissolves.
