Relation between permeability and effective stress along a plate-boundary fault, Barbados accretionary complex

Fisher, A. T.; Zwart, Gretchen; Party, Ocean Drilling Program Leg 156 Scientific

doi:10.1130/0091-7613(1996)024<0307:rbpaes>2.3.co;2

Cited by 61 publications

(36 citation statements)

References 31 publications

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“…Using a similar approach, Spinelli et al [2006] estimated that décollement permeability at the Costa Rica subduction zone must be ≥10 −14 m 2 in order to match available constraints on pore pressure and consolidation trends from boreholes. At the Barbados subduction zone, Bekins et al [1995] used an inverse modeling approach to constrain steady state décollement permeability to ∼10 −14 m 2 , which is in good agreement with values of 1 × 10 −15 m 2 to 6 × 10 −13 m 2 reported by Fisher et al [1996] from single well tests in the décollement zone.…”

Section: Discussionsupporting

confidence: 70%

Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering

Skarbek

Saffer

2009

J. Geophys. Res.

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[1] Despite its importance for plate boundary fault processes, quantitative constraints on pore pressure are rare, especially within fault zones. Here, we combine laboratory permeability measurements from core samples with a model of loading and pore pressure diffusion to investigate pore fluid pressure evolution within underthrust sediment at the Nankai subduction zone. Independent estimates of pore pressure to $20 km from the trench, combined with permeability measurements conducted over a wide range of effective stresses and porosities, allow us to reliably simulate pore pressure development to greater depths than in previous studies and to directly quantify pore pressure within the plate boundary fault zone itself, which acts as the upper boundary of the underthrusting section. Our results suggest that the time-averaged excess pore pressure (P*) along the décollement ranges from 1.7-2.1 MPa at the trench to 30.2-35.9 MPa by 40 km landward, corresponding to pore pressure ratios of l b = 0.68-0.77. For friction coefficients of 0.30-0.40, the resulting shear strength along the décollement remains <12 MPa over this region. When noncohesive critical taper theory is applied using these values, the required pore pressure ratios within the wedge are near hydrostatic (l w = 0.41-0.59), implying either that pore pressure throughout the wedge is low or that the fault slips only during transient pulses of elevated pore pressure. In addition, simulated downward migration of minima in effective stress during drainage provides a quantitative explanation for down stepping of the décollement that is consistent with observations at Nankai.Citation: Skarbek, R. M., and D. M. Saffer (2009), Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering,

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Section: Discussionsupporting

confidence: 70%

Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering

Skarbek

Saffer

2009

J. Geophys. Res.

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“…In the 1990s three separate tests were conducted to measure permeability in situ at Hole 949C in northern Barbados. These employed: down‐hole packers deployed from the drill‐ship (Fisher et al. 1996; Fisher & Zwart 1997); manipulation of flow through valves at the seafloor from a submersible (Screaton et al.…”

Section: Introductionmentioning

confidence: 99%

Reanalysis ofin situpermeability measurements in the Barbados décollement

Bekins¹,

Matmon²,

Screaton³

et al. 2010

Geofluids

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A cased and sealed borehole in the Northern Barbados accretionary complex was the site of the first attempts to measure permeability in situ along a plate boundary dé collement. Three separate efforts at Hole 949C yielded permeability estimates for the dé collement spanning four orders of magnitude. An analysis of problems encountered during installation of the casing and seals provides insights into how the borehole conditions may have led to the wide range of results. During the installation, sediments from the surrounding formation repeatedly intruded into the borehole and casing. Stress analysis shows that the weak sediments were deforming plastically and the radial and tangential stresses around the borehole were significantly lower than lithostatic. This perturbed stress state may explain why the test pressure records showed indications of hydrofracture at pressures below lithostatic, and permeabilities rose rapidly as the estimated effective stress dropped below 0.8 MPa. Even after the borehole was sealed, the plastic deformation of the formation and relatively large gap of the wire wrapped screen allowed sediment to flow into the casing. Force equilibrium calculations predict sediment would have filled the borehole to 10 cm above the top of the screen by the time slug tests were conducted 1.5 years after the borehole was sealed. Reanalysis of the slug test results with these conditions yields several orders of magnitude higher permeability estimates than the original analysis which assumed an open casing. Overall the results based on only the tests with no sign of hydrofracture yield a permeability range of 10 )14 -10 )15 m 2 and a rate of increase in permeability with decreasing effective stress consistent with laboratory tests on samples from the dé collement zone.

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“…Another detected phenomenon stressing the mechanical importance in earthquake nucleation are elevated fluid pressures at the hypocenter region of the M 7.2 1995 Kobe earthquake, Japan [ Zhao et al , 1996]. Compartmentalized high fluid pressures [ Byerlee , 1993] are supported in part by seismic and drilling experiments along a decollement near Barbados [ Moore et al , 1995; Fisher and Zwart , 1996]. Field evidence implies the formation and destruction of low permeability/diffusivity seals to drive pore pressure in excess of hydrostatic [ Sibson , 1994].…”

Section: Introductionmentioning

confidence: 99%

Stability regimes of a dilatant, fluid‐infiltrated fault plane in a three‐dimensional elastic solid

Hillers

Miller

2006

J. Geophys. Res.

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[1] We investigate in a systematic parameter space study dilatant effects on slip evolution of a fluid-infiltrated fault in the continuum limit. The fault is governed by rate-and state-dependent friction and an empirical law for porosity evolution. We focus on the response of systems as a function of fluid-related parameters, such as the degree of overpressurization, dilatancy and diffusivity. This study emphasizes the exploration of the parameter space for homogeneous along-strike properties to investigate the evolution of spatiotemporal slip depending on hydromechanical processes. Three types of responses emerge. First, system-wide unstable stick-slip develops for drained conditions, and for undrained conditions if mechanisms leading to an increase in pore space are less effective. The critical stiffness depends on hydraulic diffusivity and dilatancy, which is shown to correspond with interevent times of simulated stick-slip events. During instabilities the evolution of hydraulic variables differ significantly between drained and undrained conditions. Second, stable creep is a result of dilatant processes. Third, systems situated in transitional stability regimes develop nonuniform slip pattern in space and time, revealing a possible explanation for rupture termination and observed stable afterslip. Although these patterns are produced by models located in transition zones of the parameter space, the occurrence of heterogeneous slip evolution is persistent for an extensive range of parameter values. Since transition zones contain an broad range of plausible conditions in the crust, they do not represent extreme cases.Citation: Hillers, G., and S. A. Miller (2006), Stability regimes of a dilatant, fluid-infiltrated fault plane in a three-dimensional elastic solid,

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Relation between permeability and effective stress along a plate-boundary fault, Barbados accretionary complex

Cited by 61 publications

References 31 publications

Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering

Pore pressure development beneath the décollement at the Nankai subduction zone: Implications for plate boundary fault strength and sediment dewatering

Reanalysis ofin situpermeability measurements in the Barbados décollement

Stability regimes of a dilatant, fluid‐infiltrated fault plane in a three‐dimensional elastic solid

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