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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 authors present a theory for the radiation of high-frequency waves by earthquake faults, where they model the fault as a planar region in which the stress drops to the kinematic friction during slip and show that the high frequencies originate from the stress and slip velocity concentrations in the vicinity of the fault's edges.
Abstract: Summary. We present a theory for the radiation of high-frequency waves by earthquake faults. We model the fault as a planar region in which the stress drops to the kinematic friction during slip. This model is entirely equivalent to a shear crack. For twodimensional fault models we show that the high frequencies originate from the stress and slip velocity concentrations in the vicinity of the fault’s edges. These stress concentrations radiate when the crack expands with accelerated motion. The most efficient generation of high-frequency waves occurs when the rupture velocity changes abruptly. In this case, the displacement spectrum has an u-’ behaviour at high frequencies. The excitation is proportional to the intensity of the stress concentration near the crack tips and to the change in the focusing factor due to rupture velocity. We extend these two-dimensional results to more general three-dimensional fault models in the case when the rupture velocity changes simultaneously on the rupture front. Results are similar to those described for twodimensional faults. We apply the theory to the case of a circular fault that grows at constant velocity and stops suddenly. The present theory is in excellent agreement with a numerical solution of the same problem. Our results provide upper bounds to the high-frequency radiation from more realistic models in which rupture velocity does not change suddenly. The u-’ is the minimum possible decay at high frequencies for any crack model of the source.

339 citations

Journal ArticleDOI
TL;DR: In this paper, a new model for the origin of the Najd Fault System was proposed, based on a broad zone of NW-SE directed crustal extension that accompanied juvenile continental crustal formation in northernmost Afro-Arabia.
Abstract: The Najd Fault System is a complex set of left-lateral strike-slip faults and ductile shear zones that strike NW-SE across the Precambrian of Arabia and Egypt. This system was developed during the interval 540–620 Ma. It is up to 400 km wide with an exposed length of 1100 km; inferred buried extensions of the Najd give it a total length of 2000 km. It is the best exposed and may be the largest pre-Mesozoic zone of transcurrent faulting on earth. Previous models for the Najd Fault System suggest it formed as a result of a major Late Precambrian continent-continent collision. This model is not preferred here because (1) the lack of evidence for a pre-Late Precambrian continent to the east of the Najd Fault System; (2) the difference between the orientation of the Najd Fault System and that predicted by slip-line theory; (3) the younger age of Najd movements compared with that of collisional sutures in the Arabian Shield; and (4) lack of evidence for wide-spread crustal uplift that would be expected to accompany collision. A new model for the origin of the Najd Fault System accounts for each of these objections: The Najd Fault System formed in response to a broad zone of NW-SE directed crustal extension that accompanied juvenile continental crustal formation in northernmost Afro-Arabia. This model also accounts for the following observations: (1) Strands of the Najd parallel the direction of extension in the North Eastern Desert of Egypt and Sinai; (2) the timing of the principal rifting movements (ca. 575–600 Ma) overlap with those of the Najd (ca. 560–620 Ma); (3) in spite of observation (2), the Najd Fault System is not recognized in northernmost Afro-Arabia; instead the Najd deformation becomes increasingly ductile and these zones are more commonly intruded by sheared and foliated granites as the principal zone of extension is approached. The Najd Fault System thus represents a set of continental transforms developed in response to a major episode of Late Precambrian extensional continental crust formation in northernmost Afro-Arabia.

338 citations

Journal ArticleDOI
03 Feb 2006-Science
TL;DR: The dynamic shear resistance (τf) in the presence of friction-induced melts from both exhumed faults and high-velocity frictional experiments is estimated to be well below the Byerlee strength.
Abstract: Melt produced by friction during earthquakes may act either as a coseismic fault lubricant or as a viscous brake. Here we estimate the dynamic shear resistance (τ f ) in the presence of friction-induced melts from both exhumed faults and high-velocity (1.28 meters per second) frictional experiments. Exhumed faults within granitoids (tonalites) indicate low τ f at 10 kilometers in depth. Friction experiments on tonalite samples show that τ f depends weakly on normal stress. Extrapolation of experimental data yields τ f values consistent with the field estimates and well below the Byerlee strength. We conclude that friction-induced melts can lubricate faults at intermediate crustal depths.

337 citations

Journal ArticleDOI
05 Apr 1991-Science
TL;DR: In this paper, the authors show that deep-focus seismicity could originate from dehydration and high-pressure structural instabilities occurring in the hydrated part of the lithosphere that sinks into the upper mantle.
Abstract: For more than 50 years, observations of earthquakes to depths of 100 to 650 kilometers inside Earth have been enigmatic: at these depths, rocks are expected to deform by ductile flow rather than brittle fracturing or frictional sliding on fault surfaces Laboratory experiments and detailed calculations of the pressures and temperatures in seismically active subduction zones indicate that this deep-focus seismicity could originate from dehydration and high-pressure structural instabilities occurring in the hydrated part of the lithosphere that sinks into the upper mantle Thus, seismologists may be mapping the recirculation of water from the oceans back into the deep interior of our planet

335 citations

Journal ArticleDOI
07 Apr 2005-Nature
TL;DR: In this article, the authors show that plate unbending with distance from the top of an axial high reproduces the observed dip directions and offsets of faults formed at fast-spreading centres.
Abstract: Abyssal-hill-bounding faults that pervade the oceanic crust are the most common tectonic feature on the surface of the Earth. The recognition that these faults form at plate spreading centres came with the plate tectonic revolution. Recent observations reveal a large range of fault sizes and orientations; numerical models of plate separation, dyke intrusion and faulting require at least two distinct mechanisms of fault formation at ridges to explain these observations. Plate unbending with distance from the top of an axial high reproduces the observed dip directions and offsets of faults formed at fast-spreading centres. Conversely, plate stretching, with differing amounts of constant-rate magmatic dyke intrusion, can explain the great variety of fault offset seen at slow-spreading ridges. Very-large-offset normal faults only form when about half the plate separation at a ridge is accommodated by dyke intrusion.

335 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