Modelling of near-field subsurface displacements for generalized faults and fault arrays

Ma, Xugang; Kusznir, Nick

doi:10.1016/0191-8141(93)90007-w

Cited by 42 publications

(14 citation statements)

References 15 publications

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“…In particular, though the slip on the fault may be uniform, the horizontal displacement field at the surface is not (Ma & Kusznir 1993). In the simplest case, the maximum surface displacement occurs furthest away from the ends of the rupture zone with the effect of pulling material in towards the centre.…”

Section: Fault-slip Vectormentioning

confidence: 96%

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A simple method for estimating the horizontal velocity field in wide zones of active deformation-II. Examples from New Zealand, Central Asia and Chile

Lamb

1994

Geophysical Journal International

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SUMMARY Lamb (1994) has described a simple method for estimating the horizontal velocity field in a wide zone of active deformation. This method is now used to investigate the horizontal velocity or displacement field in part of the New Zealand plate‐boundary zone, Central Asia and southern central Chile. In each region, a range of weighted least‐squares solutions have been found, depending on assumptions about aspects of the internal deformation. In the New Zealand example, observed tectonic rotations are successfully predicted. Solutions for Central Asia place constraints on the manner in which the northward convergence of India into Eurasia is accommodated. Horizontal surface displacement fields are determined for the elastic rebound during the 1960 Chilean great earthquake, based on available retriangulation data and assumptions about the slip vector on the fault. These solutions suggest, but do not prove, a nearly pure thrust event for this earthquake.

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Section: Fault-slip Vectormentioning

confidence: 96%

“…Thus, they do not necessarily have any physical significance and do not always look like theoretical simple models of elastic rebound (Ma & Kusznir 1993). …”

Section: Fault-slip Vectormentioning

confidence: 97%

A simple method for estimating the horizontal velocity field in wide zones of active deformation-II. Examples from New Zealand, Central Asia and Chile

Lamb

1994

Geophysical Journal International

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“…The elastic dislocation model is a mechanical model that calculates the equilibrium displacement, strain and stress fields in an elastic medium resulting from localized displacements on one or more planar fault (Okada 1992;Ma & Kusznir 1993). It therefore differs from finite-element models in that it requires the fault displacements to be specified as initial boundary conditions rather than calculating these as a result of stress boundary conditions.…”

Section: Elastic Dislocation Modelling and The Impact Of Mechanical Pmentioning

confidence: 99%

Using mechanical models to investigate the controls on fracture geometry and distribution in chalk

Welch¹,

Souque

Davies³

et al. 2014

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Chalk is an important reservoir rock. However, owing to its low permeability, fractures are key to producing hydrocarbons from chalk reservoirs. Fractures in chalk usually form one of three geometric patterns: localized fractures (commonly concentric rings) developed around tips, bends and splays in larger faults; regularly spaced regional fracture sets; and fracture corridors comprising narrow zones of closely spaced parallel fractures. Localized fracture patterns are likely to give only local permeability enhancement; regional fracture sets and, especially, fracture corridors may provide long, high-permeability flow pathways through the chalk. Field mapping shows that both localized fracture patterns and fracture corridors often nucleate around larger faults; however, the fracture corridors rapidly propagate away from the faults following the regional stress orientation. It is therefore not necessary to know the detailed fault geometry to predict the geometry of the fracture corridors, although the fault density can help to predict the spacing of the fracture corridors. Mechanical modelling shows that while localized fracture patterns can form under normal fluid pressure conditions as a result of local stress anomalies around fault bends, tips and splays, fracture corridors can only form under conditions of fluid overpressure. Once they nucleate, they will continue to propagate until they either intersect another fault or the fluid pressure in them is dissipated.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.Cretaceous chalk is an important reservoir unit in the North Sea, and hosts a number of large fields in the Norwegian, Danish and UK sectors. However, the matrix permeability of chalk is generally very low (typically ,1 mD), and, hence, fractures are often important in controlling fluid flow in the subsurface and are key to producing these fields economically ( Aims and objectivesIn this study we use mechanical modelling techniques to examine the controls on fracture development and resulting geometry in chalk, and compare these results with fracture patterns observed in two chalk outcrops from southern and NE England. In particular, we will examine the relationship between fractures, fracture corridors and larger scale faults, and the impact of fluid pressure on fracture development. We will use elastic dislocation and finite-element models to investigate the in situ stress patterns developed around larger faults under different conditions of deformation and compare these with the observed fracture patterns. The elastic dislocation models simply assume the chalk to be a continuum elastic material, and take no account of fluid pressure. However, the finite-element models allow us to incorporate the effects of fluid overpressure, leading to dilation of the faults and fractures. We model two end-member cases of overpressured chalk: a case with a permeable host rock, in which the fluid overpressure results in a decrease in the effective horizontal stress; and a...

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“…Hofion et al [1995] studied the surface deformation due to dike emplacement by exact calculation of viscoelastic-gravitational Green's functions. Ma and Kusznir [1992, 1993, 1994] calculated displacements for a fully relaxed model by setting the elastic Lfirne parameters equal to their relaxed values. However, they neither calculated deformation during transient relaxation nor did they show the viscoelastic behavior.…”

Section: Paper Number 95jb03118mentioning

confidence: 99%

Surface deformation due to a strike‐slip fault in an elastic gravitational layer overlying a viscoelastic gravitational half‐space

Yu¹,

Rundle

Fernández

1996

J. Geophys. Res.

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Abstract. We extend a technique previously used to model surface displacements resulting from thrust faulting in an elastic-gravitational layer over a viscoelastic-gravitational half-space to the case of strike-slip faulting. The method involves the calculation of the Green's functions for a strike-slip point source contained in an elastic-gravitational layer over a viscoelastic-gravitational half-space. The correspondence principle of linear viscoelasticity is applied to introduce time dependence. The resulting Green' s functions are then integrated over the source region to obtain the near-field displacements. Several sample calculations are presented involving 90 ø and 30 ø dipping faults and ruptures completely and partially through the elastic layer. We also illustrate the time dependent deformation due to a buried fault. Results show that the use of a viscoelastic half-space underlying an elastic layer introduces a long wavelength component into the deformation field [Cohen and Kramer, 1984], even in cases of non vertical strike-slip fault and inclusion of gravitational effect, that cannot be modeled by purely elastic techniques. Calculations have shown that vertical postseismic displacement is insignificant and that the horizontal movement is about the same magnitude as the coseismic strike-slip displacement. The inclusion of gravity affects the horizontal displacement due to vertical strike-slip faulting in far field and the vertical displacement for dipping strike-slip faulting in near-field. The computed results have been fit to the Global Positioning System measurements of the Landers earthquake taken shortly after the main shock, assuming a relaxation time of the order of days. This relaxation time is considerably shorter than times of the order of years to decades found in previous studies. The major differences between this detailed three-dimensional and simplified two-dimensional model are the decay of magnitude in displacement field and the distinct displacement pattern in the regions beyond the fault tip. The displacement field due to the cyclic earthquakes was constructed by considering the finite fault length and inclusion of gravity. It is found that the displacement field is dominated by the plate motion in the case of short recurrence time. On the other hand, a "looping" and migrating pattern in the displacement field is found in the case of very long recurrence time, which is not seen in those 2D simplified models.

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Modelling of near-field subsurface displacements for generalized faults and fault arrays

Cited by 42 publications

References 15 publications

A simple method for estimating the horizontal velocity field in wide zones of active deformation-II. Examples from New Zealand, Central Asia and Chile

A simple method for estimating the horizontal velocity field in wide zones of active deformation-II. Examples from New Zealand, Central Asia and Chile

Using mechanical models to investigate the controls on fracture geometry and distribution in chalk

Surface deformation due to a strike‐slip fault in an elastic gravitational layer overlying a viscoelastic gravitational half‐space

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