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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 article, the authors show that left-lateral strike-slip shearing along the Red River shear zone started after 21 Ma, not at 35 Ma as previously thought, and the fault was purely a crustal structure.
Abstract: The 1000 km long NW–SE-striking, left-lateral Ailao Shan–Red River shear zone runs from the southeastern corner of Tibet to the Gulf of Tonkin and the South China Sea. It has been used as the prime example of a lithospheric-scale strike-slip fault that has accommodated between 500 and 1000 km of southeastwards extrusion of Indo-China away from the Indian plate indentor. Central to the model of continental extrusion is that such faults cut through the entire lithosphere, that shear heating resulted in high-grade metamorphism and local anatexis, and that the ages of sheared granites along the fault also date the timing of strike-slip shearing. However, structural data from the Red River shear zone clearly show that vertical strike-slip faulting post-dated metamorphism and granite emplacement. Most granites along the shear zone are mantle-related granodiorites or within-plate alkali granites formed prior to shearing along the Red River shear zone. Left-lateral kinematic indicators are ubiquitous within the Red River mylonites, but they are always lower-temperature fabrics, formed after peak sillimanite metamorphism and after granite crystallization. It is suggested that left-lateral strike-slip shearing along the Red River shear zone started after 21 Ma, not at 35 Ma as previously thought, and the fault was purely a crustal structure. None of the geological features used to propose the 500–1000 km offsets are robust, and the total finite offset remains unknown.

249 citations

Journal ArticleDOI
TL;DR: In this paper, the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement, and the results show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata.
Abstract: In contrast to kink band migration modeling methods, trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges. Modeled fold hinges tighten and converge downward, within a triangular zone of distributed deformation which is focused on the fault tip. Such features have been reported from field studies and are also seen in analogue models of compressional deformation. However, apart from its initial application to Laramide folds, little quantitative work has been undertaken on trishear fault propagation folding in other settings. In addition, no study has been undertaken into the growth strata which might be associated with such structures. This paper uses an equivalent velocity description of the geometric model of trishear, together with models of erosion and sedimentation, to investigate trishear fault propagation folding of both pregrowth and growth strata. The trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement. The models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata. When total slip on a structure is high, the model predicts overturned pregrowth and growth strata. During the initial stages of deformation, beds in the forelimb thicken but later thin when they become steep or overturned. The effect of variations in fault propagation to slip ratios on two-dimensional finite strain in the models is assessed by the use of initially circular strain markers. High fault propagation to slip (p/s) ratios lead to narrow zones of high finite strain, while lower p/s ratios lead to more ductile deformation and broader zones of high strain. In all cases, hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault. Modeled structures are compared with natural examples.

248 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed three-dimensional finite difference solutions for a simple shear-crack model of faulting to determine the effects of fault length and width on the earthquake slip function.
Abstract: We analyze three-dimensional finite difference solutions for a simple shear-crack model of faulting to determine the effects of fault length and width on the earthquake slip function. The fault model is dynamic, with only rupture velocity, fault dimensions, and dynamic stress-drop prescribed. The numerical solutions are accurate for frequencies up to 5 Hz, and are combined with asymptotic results for shear cracks in order to characterize the slip function at higher frequencies. Near the hypocenter, the slip velocity exhibits a square-root singularity whose intensity increases with hypocentral distance. At distances greater than the fault width, w , growth of the velocity intensity ceases, and the slip function becomes nearly invariant with distance along the fault length. Closed-form expressions are developed for the dependence of static slip ( s ∞), slip rise time ( TR ), and slip velocity intensity ( V ) on fault geometry. Along the center line of a long, narrow fault, at hypocentral distances exceeding w , these expressions reduce to s ∞ ≈ w Δτ/μ, TR ≈ 0.5 w/vR , and V ≈ √ w /2 vR Δτ/μ, where Δτ is the dynamic stress drop, μ the shear modulus, and vR the rupture velocity. The numerical results imply that uniform-dislocation kinematic earthquake models in which slip is represented by a ramp time function will underpredict high-frequency ground motion relative to low-frequency ground motion. A further implication of the numerical solutions is that the nature of inelastic processes at the advancing edge of a long fault will depend on fault width, but will be independent of rupture length.

248 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the North Anatolian Fault system and the linked basins in the eastern Marmara Sea using newly acquired multi-channel seismic reflection data.

248 citations

Book
19 Nov 2007
TL;DR: In this paper, the authors present a survey of the effects of treetops on the stability of the North America-Pacific Plate boundary, including the following: 1.1 Themes and Topics.
Abstract: Preface. 1 Scrunch and Stretch Bedrock Uplift. 1.1 Introduction. 1.2 Pure Uplift, Stretch and Scrunch Bedrock Uplift. 1.2.1 Isostatic and Tectonic Uplift. 1.2.2 Stretch and Scrunch Tectonics. 1.3 Landscape Responses to Regional Uplift. 2 Concepts for Studies of Rising Mountains. 2.1 Themes and Topics. 2.2 The Fundamental Control of Base Level. 2.2.1 Base Level. 2.2.2 Base Level Change. 2.2.3 The Base Level of Erosion. 2.2.4 The Changing Level of the Sea. 2.2.5 Spatial Decay of the Effects of Local Base Level Changes. 2.3 Threshold of Critical Power in Streams. 2.3.1 Relative Strengths of Stream Power and Resisting Power. 2.3.2 Threshold-Intersection Points. 2.4 Equilibrium in Streams. 2.4.1 Classification of Stream Terraces. 2.4.2 Feedback Mechanisms. 2.4.3 Dynamic and Static Equilibrium. 2.5 Time Lags of Response. 2.5.1 Responses to Pulses of Uplift. 2.5.2 Perturbations that Limit Continuity of Fluvial Systems. 2.5.3 Lithologic and Climatic Controls of Relaxation Times. 2.5.4 Time Spans Needed to Erode Landforms. 2.6 Tectonically-Induced Downcutting. 2.6.1 Straths, Stream-Gradient Indices, and Strath Terraces. 2.6.2 Modulation of Stream-Terrace Formation by Climatic Changes. 2.7 Nontectonic Base-Level Fall and Strath Terrace Formation. 2.8 Hydraulic Coordinates. 3 Mountain Fronts. 3.1 Introduction. 3.2 Tectonically Active Escarpments. 3.2.1 Faceted Spur Ridges. 3.2.2 Mountain-Piedmont Junctions. 3.2.3 Piedmont Forelands. 3.3 Fault Segmentation of Mountain Fronts. 3.3.1 Different Ways to Study Active Faults. 3.3.2 Segmentation Concepts and Classification. 3.3.3 Fault-Segment Boundaries. 3.3.4 Normal Fault Surface Ruptures. 3.3.5 Strike-Slip Fault Surface Ruptures. 3.4 Summary. 4 Tectonic Activity Classes of Mountain Fronts. 4.1 Tectonic Setting of the North America-Pacific Plate Boundary. 4.2 Appraisal of Regional Mountain Front Tectonic Activity. 4.2.1 Geomorphic Tools For Describing Relative Uplift Rates. 4.2.1.1 Mountain-Front Sinuosity. 4.2.1.2 Widths of Valleys. 4.2.1.3 Triangular Facets. 4.2.2 Diagnostic Landscape Classes of Relative Tectonic Activity. 4.2.3 Regional Assessments of Relative Tectonic Activity. 4.2.3.1 Response Time Complications and Strike-Slip Faulting. 4.2.3.2 Maps of Relative Uplift. 4.3 Summary. 5 Fault Scarps. 5.1 General Features. 5.2 Scarp Morphology Changes with Time. 5.2.1 Changes in Scarp Height. 5.2.2 Decreases in Maximum Scarp Slope. 5.2.3 Diffusion-Equation Modeling. 5.3 Climatic Controls of Fault-Scarp Morphology. 5.4 Lithologic Controls of Fault-Scarp Morphology. 5.4.1 Fault Rupture of Different Materials. 5.4.2 Lithologic Controls on an 1887 Fault Scarp. 5.4.2.1 Geomorphic Processes. 5.4.2.2 Scarp Materials. 5.4.2.3 Scarp Morphology. 5.5 Laser Swath Digital Elevation Models. 5.6 Dating Fault Scarps with Terrestrial Cosmogenic Nuclides. 5.6.1 Alluvium. 5.6.2 Bedrock. 5.7 Summary. 6 Analyses of Prehistoric Seismic Shaking. 6.1 Paleoseismology Goals. 6.2 Earthquake-Generated Regional Rockfall Events. 6.2.1 New Zealand Earthquakes. 6.2.1.1 Tectonic Setting. 6.2.1.2 Background and Procedures. 6.2.1.3 Diagnostic Lichen-Size Peaks. 6.2.1.3 Tree-Ring Analyses. 6.2.1.5 Alpine Fault Earthquakes. 6.2.1.6 Recent Marlborough Earthquakes. 6.2.2 California Earthquakes. 6.2.2.1 Calibration of Lichen Growth Rates. 6.2.2.2 Recent Cliff Collapse. 6.2.2.3 Rockfall Processes in Glaciated Valleys. 6.2.2.4 San Andreas Fault Earthquakes. 6.2.2.5 Lichenometry and Precise Radiocarbon Dating Methods. 6.3 Summary. References Cited. Index

248 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