The Grimsey hydrothermal field offshore North Iceland: crustal structure, faulting and related gas venting

Riedel, Carsten; Schmidt, Mark; Botz, R.; Theilen, F.

doi:10.1016/s0012-821x(01)00519-2

Cited by 32 publications

(18 citation statements)

References 37 publications

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“…A pertinent feature emerging from our simulations is that deeper faults have comparatively high pore pressures causing λ to vary between 0.6 and 1 because they focus fluid flow at depth. Upwards fluid migration in the faults of the TFZ is thought to lead to intense microseismicity [ Riedel et al , 2001; Stefánsson et al , 2008]. Our simulations offer an explanation for this phenomenon (Figure 12): when faults inflate, pulses of overpressured fluids move upwards in the fault enhancing its permeability.…”

Section: Discussionmentioning

confidence: 81%

Numerical simulations of seismicity-induced fluid flow in the Tjörnes Fracture Zone, Iceland

Lupi¹,

Geiger²,

Graham³

2011

J. Geophys. Res.

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[1] We use high-resolution simulations to analyze fluid flow, pore pressure, and fault permeability evolution in the seismically active Tjörnes Fracture Zone (TFZ), a major transform fault zone in the North of Iceland. Our results show that the TFZ is characterized by four distinct areas where pore pressures are above hydrostatic, consistent with geophysical observations. Basement and faults, which are assumed to have low permeabilities, often display pore pressures close to lithostatic. Fault permeabilities are allowed to vary freely as a function of the effective fault normal stress. They hence inflate periodically to release excess pore pressure in a few minutes. This is accompanied by an increase in permeability of over seven orders of magnitude and causes short-lived fluid fluxes of more than 0.01 m s −1. After pore pressures have dissipated, fault permeabilities decay back to their original values in 2 to 3 years as the effective fault normal stress increases. This behavior is consistent with a toggle switch mechanism and could have two important implications for fluid flow in seismically and hydrothermally active oceanic crust. First, the rapid changes in fault permeability and pore pressure provide an explanation for distinct cyclical geochemical changes observed on a similar timescale in thermal waters near the town of Húsavik in the TFZ before and after a magnitude 5.8 M w earthquake. Second, our results provide another line of evidence in the growing number of observations that crustal permeabilities are constantly evolving and geological processes in hydrothermal systems can be dominated by short-lived and extreme flow events.

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Section: Discussionmentioning

confidence: 81%

Numerical simulations of seismicity-induced fluid flow in the Tjörnes Fracture Zone, Iceland

Lupi¹,

Geiger²,

Graham³

2011

J. Geophys. Res.

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“…These grabens are generally interpreted in terms of fault wedge or pull‐apart basin related to strike‐slip fault tectonic activity [ Riedel et al , 2001]. NNW–SSE normal faults are also well developed between the HFF and the GF [ McMaster et al , 1977; Riedel et al , 2001]. Despite this complexity, and although fault offset data are few because most of the transform zone is located offshore, geological evidence leads to consider the TFZ as a genuine right‐lateral transform fault zone, not an overlapping spreading center between two rifts segments.…”

Section: Tjörnes Fracture Zonementioning

confidence: 99%

Fault interaction and stresses along broad oceanic transform zone: Tjörnes Fracture Zone, north Iceland

et al. 2010

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“…We focus here on stress inversion results from the central portion of the Grímsey lineament, south of the Grímsey hydrothermal field (Riedel et al 2001) and the site of intense seismic activity in recent years. Our data set contains 1653 earthquakes recorded by the Icelandic SIL network (South Iceland Lowland; Bödvarsson et al 1999) between October 2000 and March 2006.…”

Section: Controls On the Axis Of Maximum Horizontal Compressive Stressmentioning

confidence: 99%

Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor

Lund¹,

Townend²

2007

Geophysical Journal International

242

142

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S U M M A R YEarthquakes potentially serve as abundant and cost-effective gauges of tectonic stress provided that reliable means exist of extracting robust stress parameters. Several algorithms have been developed for this task, each of which typically provides information on the orientations of the three principal stresses and a single stress magnitude parameter. A convenient way of displaying tectonic stress results is to map the azimuth of maximum horizontal compressive stress, which is usually approximated using the azimuth of the larger subhorizontal principal stress. This approximation introduces avoidable errors that depend not only on the principal stress axes' plunges but also on the value of the stress magnitude parameter. Here we outline a method of computing the true direction of maximum horizontal compressive stress (S H ) and show that this computation can be performed using only the four stress parameters obtained in routine focal mechanism stress estimation. Using theoretical examples and new stress inversion results obtained with focal mechanism data from the central Grímsey lineament, northern Iceland, we show that the S H axis may differ by tens of degrees from its commonly adopted proxy. In order to most appropriately compare tectonic stress estimates with other geophysical parameters, such as seismic fast directions or geodetically measured strain rate tensors, or to investigate spatiotemporal variations in stress, we recommend that full use be made of the routinely estimated stress parameters and that a formal axis of maximum horizontal compression be calculated.

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The Grimsey hydrothermal field offshore North Iceland: crustal structure, faulting and related gas venting

Cited by 32 publications

References 37 publications

Numerical simulations of seismicity-induced fluid flow in the Tjörnes Fracture Zone, Iceland

Numerical simulations of seismicity-induced fluid flow in the Tjörnes Fracture Zone, Iceland

Fault interaction and stresses along broad oceanic transform zone: Tjörnes Fracture Zone, north Iceland

Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor

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