Evidence for weak oceanic transform faults

Behn, M. D.; Lin, Jian; Zuber, M. T.

doi:10.1029/2002gl015612

Cited by 65 publications

(41 citation statements)

References 18 publications

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“…One scenario for the means by which extensional stresses could be dissipated without propagation is through the formation of oblique normal faults. Oblique normal faults or normal faults with unusually long throws (Behn et al, 2002b) will result in crustal thinning. Because the generation of melt from the mantle is controlled by pressure, temperature, and the composition of the mantle, the release of pressure over a mantle body may result in the generation of mantle melt (McKenzie and Bickle, 1988).…”

Section: Discussionmentioning

confidence: 99%

Stress-induced seamount formation at ridge-transform intersections

Beutel

2005

Plates, Plumes and Paradigms

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Our current understanding of thermal and physiographic gradients at the ridge suggests that hotspot (or buoyant melt) will be directed to the center of ridge segments and away from the ridge-transform intersections (RTIs). However, hotspots located at RTIs can be found on almost every spreading ridge across the planet. Finite element models are used to demonstrate that increasing transform strength dramatically increases extensional stresses at RTIs. Several models are presented that suggest that increased extensional stress at RTIs may result in adiabatic melting, thinning of the lithosphere, and consequently a change in the physiographic and thermal gradient at the ridge. Whether this change results in the formation of a hotspot, the propagation of the ridge, or the formation of a new weak transform is dependent on a variety of factors. However, it appears that hotspot formation at RTIs may be the result of lithospheric processes rather than deep-seated mantle plumes.

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Section: Discussionmentioning

confidence: 99%

Stress-induced seamount formation at ridge-transform intersections

Beutel

2005

Plates, Plumes and Paradigms

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“…Initiation of subduction by either small‐scale convection or plate forces requires that the lithosphere has to be weak: the apparent strength of the subduction zone has to be about one order of magnitude smaller than that suggested by experiments on rock deformation. The weakness of the lithospheric plates has various manifestations: small stress drop during earthquakes [ Kanamori , 1994], the lack of large thermal anomaly over major faults [ Lachenbruch and Sass , 1980], small apparent viscosity of the bending plates [ Kaula , 1980], and small stresses on faults in the subduction zones [ Zhong and Gurnis , 1994] as well as on transform faults in the oceanic region [ Behn et al , 2002]. It should be emphasized that only some parts of the lithosphere have to be weak.…”

Section: Discussionmentioning

confidence: 99%

Initiation of subduction by small‐scale convection

Solomatov

2004

J. Geophys. Res.

120

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[1] The possibility of initiation of subduction by sublithospheric small-scale convection is investigated with the help of Fowler's theory, numerical constraints on the lithospheric stresses generated by convection, and direct numerical simulations of subduction. The derived scaling laws show that the critical yield stress for initiation of subduction by small-scale convection is of the order of 30 MPa. This value is comparable with the critical yield stress required for initiation of subduction by plate forces and with the estimates of stresses in the subduction zone. This implies that small-scale convection can play an important role in the initiation of subduction on the present-day Earth. This also implies that small-scale convection can initiate subduction in the absence of already occurring plate tectonics and thus can be a trigger mechanism for plate tectonics on the early Earth and other terrestrial planets. The critical yield stress for initiation of subduction by either mechanism is at least one order of magnitude smaller than the estimates of the lithospheric strength suggested by laboratory experiments on rock deformation. Such a low lithospheric strength is most likely caused by a relatively high abundance of water in the interior of the Earth. Since the critical yield stress depends only weakly on planetary parameters, water seems to be the key condition required for plate tectonics to occur on a terrestrial planet.

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“…Comparisons of abyssal hill fabric near transforms to predictions of fault patterns from modeling suggest that mechanical coupling across the fault is weak on geologic time scales (Behn et al, 2002). Furthermore, serpentinized peridotites are frequently dredged in transform valleys and valley walls (Cannat et al, 1991;Dick et al, 1991), which may promote frictional weakening (Escartín et al, 2001;Rutter and Brodie, 1987).…”

Section: Influence Of Fault Zone Rheology On Transform Thermal Structurementioning

confidence: 99%

Thermal structure of oceanic transform faults

Behn

Boettcher

Hirth

2007

Geol

Self Cite

106

111

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We use three-dimensional fi nite element simulations to investigate the temperature structure beneath oceanic transform faults. We show that using a rheology that incorporates brittle weakening of the lithosphere generates a region of enhanced mantle upwelling and elevated temperatures along the transform; the warmest temperatures and thinnest lithosphere are predicted to be near the center of the transform. Previous studies predicted that the mantle beneath oceanic transform faults is anomalously cold relative to adjacent intraplate regions, with the thickest lithosphere located at the center of the transform. These earlier studies used simplifi ed rheologic laws to simulate the behavior of the lithosphere and underlying asthenosphere. We show that the warmer thermal structure predicted by our calculations is directly attributed to the inclusion of a more realistic brittle rheology. This temperature structure is consistent with a wide range of observations from ridge-transform environments, including the depth of seismicity, geochemical anomalies along adjacent ridge segments, and the tendency for long transforms to break into small intratransform spreading centers during changes in plate motion.

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Evidence for weak oceanic transform faults

Cited by 65 publications

References 18 publications

Stress-induced seamount formation at ridge-transform intersections

Stress-induced seamount formation at ridge-transform intersections

Initiation of subduction by small‐scale convection

Thermal structure of oceanic transform faults

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