The importance of small-scale faulting in regional extension

Walsh, John J.; Watterson, J.; Yielding, Graham

doi:10.1038/351391a0

Cited by 282 publications

(115 citation statements)

References 15 publications

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“…Buck [1993] suggested that low-angle faults initiate at steeper angles and subsequently rotate to shallower angles. Alternative explanations argue that extension is not well estimated because of the limited resolution of seismic data and hence smaller faults or a previous generation of faults contributing to the total amount of extension is unrecognized [Reston, 2007 ;Marett and Allmendinger, 1992 ;Walsh et al 1991]. An alternative to these models is that much of the extension is not caused by large arrays of faults working simultaneously, but as extension progresses, strain localizes into a relatively narrow rift center via sequential faulting [Ranero and P erez-Gussinye, 2010].…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have shown that the amount of fault displacement imaged on seismic cross sections cannot easily explain the vertical crustal thinning estimated from wide-angle seismic studies. This phenomenon is known as the extension discrepancy [White, 1990 ;Walsh et al, 1991 ;Reston, 2007]. Another observation is that rifts seem to be asymmetric in extensional style.…”

Section: Introductionmentioning

confidence: 99%

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Early‐stage rifting of the northern Tyrrhenian Sea Basin: Results from a combined wide‐angle and multichannel seismic study

Moeller

Grevemeyer

Ranero

et al. 2013

Geochem Geophys Geosyst

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[1] Extension of the continental lithosphere leads to the formation of rift basins and ultimately may create passive continental margins. The mechanisms that operate during the early stage of crustal extension are still intensely debated. We present the results from coincident multichannel seismic and wide-angle seismic profiles that transect across the northern Tyrrhenian Sea Basin. The profiles cross the Corsica Basin (France) to the Latium Margin (Italy) where the early-rift stage of the basin is well preserved. We found two domains, each with a distinct tectonic style, heat flow and crustal thickness. One domain is the Corsica Basin in the west that formed before the main rift phase of the northern Tyrrhenian Sea opening ($8-4 Ma). The second domain is rifted continental crust characterized by tilted blocks and half-graben structures in the central region and at the Latium Margin. These two domains are separated by a deep ($10 km) sedimentary complex of the eastern portion of the Corsica Basin. Travel-time tomography of wide-angle seismic data reveals the crustal architecture and a subhorizontal 15-17 6 1 km deep Moho discontinuity under the basin. To estimate the amount of horizontal extension we have identified the pre-, syn-, and post-tectonic sedimentary units and calculated the relative displacement of faults. We found that major faults initiated at angles of 45 -50 and that the rifted domain is horizontally stretched by a factor of $ 1.3 ($8-10 mm/a). The crust has been thinned from $24 to $17 km indicating a similar amount of extension ($30%). The transect represents one of the best imaged early rifts and implies that the formation of crustal-scale detachments, or long-lived low-angle normal faults, is not a general feature that controls the rift initiation of continental crust. Other young rift basins, like the Gulf of Corinth, the Suez Rift or Lake Baikal, display features resembling the northern Tyrrhenian Basin, suggesting that half-graben formations and distributed homogeneous crustal thinning are a common feature during rift initiation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Early‐stage rifting of the northern Tyrrhenian Sea Basin: Results from a combined wide‐angle and multichannel seismic study

Moeller

Grevemeyer

Ranero

et al. 2013

Geochem Geophys Geosyst

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“…when the amount of extension is the same at all depths in a continental plate) to passive margins has resulted in the identification of subsidence anomalies, usually in the form of greater subsidence than would be expected from the degree of extension as measured on normal faults identified within the upper crust in seismic profiles (Driscoll and Karner 1998;Davis and Kusznir 2004;Clift et al 2002;Boillot et al 1988;Lister et al 1991). Not all brittle extension is identified on industrial style, deeppenetrating seismic reflection profiles (Walsh et al 1991). Nonetheless, the anomalies found in passive margins are so large that even accounting for this uncertainty does not resolve the mismatch between the total amount of subsidence recorded.…”

Section: Introductionmentioning

confidence: 99%

Coupled onshore erosion and offshore sediment loading as causes of lower crust flow on the margins of South China Sea

Clift

2015

Geosci. Lett.

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Hot, thick continental crust is susceptible to ductile flow within the middle and lower crust where quartz controls mechanical behavior. Reconstruction of subsidence in several sedimentary basins around the South China Sea, most notably the Baiyun Sag, suggests that accelerated phases of basement subsidence are associated with phases of fast erosion onshore and deposition of thick sediments offshore. Working together these two processes induce pressure gradients that drive flow of the ductile crust from offshore towards the continental interior after the end of active extension, partly reversing the flow that occurs during continental breakup. This has the effect of thinning the continental crust under super-deep basins along these continental margins after active extension has finished. This is a newly recognized form of climate-tectonic coupling, similar to that recognized in orogenic belts, especially the Himalaya. Climatically modulated surface processes, especially involving the monsoon in Southeast Asia, affects the crustal structure offshore passive margins, resulting in these "load-flow basins". This further suggests that reorganization of continental drainage systems may also have a role in governing margin structure. If some crustal thinning occurs after the end of active extension this has implications for the thermal history of hydrocarbon-bearing basins throughout the area where application of classical models results in over predictions of heatflow based on observed accommodation space.

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“…Continental-scale structures experiencing large elastic-plastic deformations typically undergo a succession of instabilities. For instance, a plate in extension will deform initially in a uniform fashion until, at a critical stress level, a neck forms around the symmetry axis of the deformation (BIOT, 1965;BUCK 1991;ENGLAND, 1983;GIBBS, 1984;HILL and HUTCHINSON, 1975;MORESI and MUHLHAUS, 2006;TVERGAARD et al, 1981;WALSH et al, 1991). Subsequently, shear bands form within the region of the neck.…”

Section: Introductionmentioning

confidence: 99%

Shear Band Formation in Numerical Simulations Applying a Continuum Damage Rheology Model

Finzi

Mühlhaus

Gross

et al. 2012

Pure Appl. Geophys.

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Abstract-In seismically active regions, faults nucleate, propagate, and form networks that evolve over time. To simulate crustal faulting processes, including the evolution of fault-zone properties, a rheological model must incorporate concepts such as damage rheology that describe the various stages of the seismic cycle (strain localization, subcritical crack growth and macroscopic failure) while accounting for material degradation and healing and off-fault deformation. Here we study the fundamental patterns of strain-localisation within the framework of a continuum damage rheology by performing a shear band analysis (linear instability analysis) and comparing predictions of shear band orientations with numerical results of the nonlinear problem. We find (analytically and numerically) that the angle between the shear band and the less compressive (transverse) direction is between 47°in compression tests with a strain ratio of 0.25 (highly confined compression test), and 60°for a strain ratio higher than 1.4 (axial compression and transverse extension). In addition we find that shear bands exhibit local dilation (I 1 [ 0) in a wide range of strain ratios excluding only simulations with highly confined compression (which yield compacting shear bands or non-localized deformation). Finally, we discuss the applicability of the damage model for simulating deformation in the seismogenic, brittle crust.

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The importance of small-scale faulting in regional extension

Cited by 282 publications

References 15 publications

Early‐stage rifting of the northern Tyrrhenian Sea Basin: Results from a combined wide‐angle and multichannel seismic study

Early‐stage rifting of the northern Tyrrhenian Sea Basin: Results from a combined wide‐angle and multichannel seismic study

Coupled onshore erosion and offshore sediment loading as causes of lower crust flow on the margins of South China Sea

Shear Band Formation in Numerical Simulations Applying a Continuum Damage Rheology Model

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