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Fault (geology)

About: Fault (geology) is a research topic. Over the lifetime, 26732 publications have been published within this topic receiving 744535 citations.


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Journal ArticleDOI
TL;DR: In this paper, the physical properties of serpentinites and their role in tectonic processes were viewed, where deformation is localized in a ~100 m thick shear zone at the footwall of detachment zones dominated by serpentine derived minerals.

185 citations

Journal ArticleDOI
TL;DR: In this paper, a large fan at the mouth of Wadi Dahal has been displaced by about 500 m since the bulk of the fanglomerates were deposited 77-140 kyr ago, as dated from cosmogenic isotope analysis (Be in chert) of pebbles collected on the fan surface and from the age of transgressive lacustrine sediments capping the fan.
Abstract: The Araba valley lies between the southern tip of the Dead Sea and the Gulf of Aqaba. This depression, blanketed with alluvial and lacustrine deposits, is cut along its entire length by the Dead Sea fault. In many places the fault is well defined by scarps, and evidence for left-lateral strike-slip faulting is abundant. The slip rate on the fault can be constrained from dated geomorphic features displaced by the fault. A large fan at the mouth of Wadi Dahal has been displaced by about 500 m since the bulk of the fanglomerates were deposited 77–140 kyr ago, as dated from cosmogenic isotope analysis (^(10)Be in chert) of pebbles collected on the fan surface and from the age of transgressive lacustrine sediments capping the fan. Holocene alluvial surfaces are also clearly offset. By correlation with similar surfaces along the Dead Sea lake margin, we propose a chronology for their emplacement. Taken together, our observations suggest an average slip rate over the Late Pleistocene of between 2 and 6 mm yr^(−1), with a preferred value of 4 mm yr^(−1). This slip rate is shown to be consistent with other constraints on the kinematics of the Arabian plate, assuming a rotation rate of about 0.396° Myr^(−1) around a pole at 31.1°N, 26.7°E relative to Africa.

185 citations

Journal ArticleDOI
TL;DR: Fluid infiltration into fault zones and their deeper-level counterparts, brittle-ductile shear zones, is examined in diverse tectonic environments in this paper, where the authors show that these transcrustal faults were used as a conduit for the ascent of trondhjemitic magmas from the base of the crust and of alkaline magmas of the asthenosphere and for discharge of thousands of cubic kilometres of hydrothermal fluids.
Abstract: Fluid infiltration into fault zones and their deeper-level counterparts, brittle-ductile shear zones, is examined in diverse tectonic environments In the 27 Ga Abitibi greenstone belt, major tectonic discontinuities, with lateral extents of hundreds of kilometres initiated as listric normal faults accommodating rift extension and acted as sites for komatiite extrusion and locally intense metasomatism During reverse motion on the structures, accommodating shortening of the belt, these transcrustal faults were utilised as a conduit for the ascent of trondhjemitic magmas from the base of the crust and of alkaline magmas from the asthenosphere and for the discharge of thousands of cubic kilometres of hydrothermal fluids Such fluids were characterised by δ18O=+6±2, δD=−50±20, δ13C=−4±4, and temperatures of 270 to 450°C, probably derived from devolatilisation of crustal rocks undergoing prograde metamorphism Hydrothermal fluids were more radiogenic (87Sr/86Sr=07010 to 07040) and possessed higher μ than did contemporaneous mantle, komatiites or tholeiites, and thus carried a contribution from older sialic basement A provinciality of87Sr/86Sr and δ13C is evident, signifying that fault plumbing sampled lower crust which was heterogeneous at the scale of tens of kilometres Mineralised faults possess enrichments of large ion lithophile (LIL), LIL elements, including K, Rb, Ba, Cs, B, and CO2, and rare elements, such as Au, Ag, As, Sb, Se, Te, Bi, and W Fluids were characterised by XCO 2≈01, neutral to slightly acidic pH, low salinity ≤3 wt-%, K/Na=01, they carried minor CH4, CO, and N2, and they underwent transient effervescence of CO2 during decompression Clastic sediments occupy graben developed at fault flexures The40Ar/39Ar release spectra indicate that fault rocks experienced episodic disturbance on time scales of hundreds of millions of years At the Grenville front, translation was accommodated along two mylonite zones and an intervening boundary fault The high-temperature (580°C) and low-temperature (430 to 490°C) mylonite zones, formed in the presence of deep-level crust-equilibrated fluids of metamorphic origin Late brittle faults contain quartz veins precipitated from fluids with extemely negative δ18O (−14 per mil) at 200 to 300°C The water may have been derived from downward penetration into fault zones of precipitation of low18O on a mountain range induced by continental collision, with uplift accommodated at deep levels by the mylonite zones coupled with rebound on the boundary faults Archean gneisses overlie Proterozoic sediments along thrust surfaces at Lagoa Real, Brazil; the gneisses are transected by brittle-ductile shear zones locally occupied by uranium deposits Following deformation at 500 to 540°C, in the presence of metamorphic fluids and under conditions of low water-to-rock ratio, shear zones underwent local intense oxidation and desilication All minerals undergo a shift of −10 per mil, indicating discharge of meteoric-water-recharged formation brines in the underlying Proterozoic sediments up through the Archean gneisses, during overthrusting; ≈1000 km3 of solutions passed through these structures The shear zones and Proterozoic sediments are less radiogenic (87Sr/86Sr=0720) than contemporaneous Archean gneisses (0900), corroborating the transport of fluids and solutes through the structure from a large external reservoir Major crustal detachment faults of Tertiary age in the Picacho Cordilleran metamorphic core complex of Arizona show an upward transition from undeformed granitic basement through mylonitic to brecciated and hydrothermally altered counterparts The highest tectonic levels are allochthonous, oxidatively altered Miocene volcanics This transition is accompanied by an increase of 12 per mil in δ18O, from +7 to +19, and a 400°C decrease in temperature Lower tectonic levels acted as aquifers for the expulsion of large volumes of higher-temperature reduced metamorphic fluids and/or evolved formation brines The Miocene allochthon was influenced by a lower-temperature reservoir inducing oxidative potassic alteration; mixing occurred between cool downward-penetrating thermal waters and the hot, deeper aqueous reservoir In general, flow regimes in these fault and shear zones follow a sequence, from conditions of high temperature and pressure with locally derived fluids at low water-to-rock ratios, during initiation of the structures, to high fluxes of reduced formation or metamorphic fluids along conduits as the structures propagate and intersect hydrothermal reservoirs Later in the tectonic evolution and at shallower crustal levels there was incursion of oxidising fluids from near-surface reservoirs into the faults In general, magmatism, tectonics, and fluid motion are intimately related

184 citations

Journal ArticleDOI
03 Jan 2008-Nature
TL;DR: It is shown that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain, indicating a strain memory in the granular material.
Abstract: It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed 1–6 . Earthquake nucleation is usually observed to take place at depths of 10–20km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick–slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normalstress,andsubjecttotransientorcontinuousperturbation by acoustic waves. Here we show that small-magnitude failure events,correspondingtotriggeredaftershocks,occurwhenapplied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. Laboratorystudiesofgranular friction haveemerged asapowerful tool for investigating tectonic fault zone processes and earthquake phenomena, including post-seismic slip, interseismic frictional restrengthening and earthquake nucleation 7,8 . Here we explore experimentallytheeffectsofdynamicloadingonstick–slipbehaviour and discuss how our results may affect understanding of earthquake processes—in particular dynamic earthquake triggering and stick– slip recurrence. Dynamic earthquake triggering involves seismic waves from one earthquake promoting or inhibiting failure on the faults they disturb. Dynamic triggering has been clearly documented in a few cases far from an earthquake source, at distances much greater than the fault radius of the triggering source 1–4,6 (outside the traditional ‘aftershock zone’), and increasing evidence suggests that it commonly occurs near the earthquake source 5,9 . Experiments on sheared layers of glass beads (like those shown in

184 citations

Journal ArticleDOI
TL;DR: In this paper, the scaling properties of two natural fault surfaces (Vuache strike-slip fault, France, and Magnola normal fault, Italy) in limestones were investigated.
Abstract: Accurate description of the topography of active faults surfaces represents an important geophysical issue because this topography is strongly related to the stress distribution along fault planes, and therefore to processes implicated in earthquake nucleation, propagation, and arrest. With the recent development of Light Detection And Ranging (LIDAR) apparatus, it is now possible to measure accurately the 3D topography of rough surfaces with a comparable resolution in all directions, both at field and laboratory scales. In the present study, we have investigated the scaling properties including possible anisotropy properties of several outcrops of two natural fault surfaces (Vuache strike-slip fault, France, and Magnola normal fault, Italy) in limestones.

184 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20234,903
202210,233
20211,417
2020998
2019966