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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, a new quantitative method for identifying fault-generated topography in swath bathymetry data by measuring topographic curvature is described. But the method cannot distinguish volcanic from fault generated topography.
Abstract: Both volcanism and faulting contribute to the rugged topography that is created at the Mid-Atlantic Ridge (MAR) and preserved off-axis in Atlantic abyssal hill terrain. Distinguishing volcanic from fault-generated topography is essential to understanding the variations in these processes and how these variations are affected by the three-dimensional pattern of mantle upwelling, ridge segmentation, and offsets. Here we describe a new quantitative method for identifying fault-generated topography in swath bathymetry data by measuring topographic curvature. The curvature method can distinguish large normal faults from volcanic features, whereas slope methods cannot because both faults and volcanic constructs can produce steep slopes. The combination of curvature and slope information allows inward and outward facing fault faces to be mapped. We apply the method to Sea Beam data collected along the MAR between 28° and 29°30′N. The fault styles mapped in this way are strongly correlated with their location within the ridge segmentation framework: long, linear, small-throw faults occur toward segment centers, while shorter, larger-throw, curved faults occur toward ends; these variations reflect those of active faults within the axial valley. We investigate two different physical mechanisms that could affect fault interactions and thus underlie variations in abyssal hill topography at the MAR. In the first model only one fault is active at a time on each side of the rift valley. Each fault grows while migrating away from the volcanic center due to dike injection; extension across the fault causes a flexural rotation of nearby inactive faults. The amount of stress necessary to displace the fault increases as the fault grows. When reaching a critical size the fault stops growing as fault activity jumps inward as a new fault starts its growth near the rift valley. This model yields a realistic terracelike morphology from the rift valley floor into the rift mountains; the relief is caused by the net rotation accumulated in the lithosphere from the active faults (e.g., 10° reached 20 km from the active fault). Fault spacing is controlled by lithospheric thickness, fault angle, and the ratio of amagmatic to magmatic extension. We hypothesize that this mechanism may be dominant toward ridge segment offsets. An alternative model considers multiple active faults; each fault relieves stresses as it grows and inhibits the growth of nearby faults, causing a characteristic fault spacing. Such fault interactions would occur in a region of necking instability involving deformation over an extended area. This mode of extension would drive a feedback mechanism that would act to regulate the size of nearby faults. We hypothesize that this mechanism may be active in the relatively weak regions of strong mantle upwelling near segment midpoints, causing the homogeneous abyssal hill fabric in these regions.

152 citations

Journal ArticleDOI
TL;DR: In this article, the four main types of fault structure are defined as simple, subsidence, gravity-graben, and longitudinal step-fault types, and the origin and nature of each type is discussed.
Abstract: The earthquakes of December 16, 1954, were accompanied by offsets along many faults in four main zones of a north-trending belt 60 miles long by 20 miles wide. Minor geologic effects included changed flow of springs and wells, formation of water fountains and craters, landslips, landslides, mudflows, and rockfalls, and secondary fracturing of unconsolidated sediments. The fault displacements were mainly along normal faults of the Basin-Range type in the following zones: (1) west of Dixie Valley, (2) southeast of Dixie Valley, (3) east of Fairview Peak, and (4) east of Stingaree Valley. The maximum strike-slip component was 12 feet (right-lateral) at Fairview Peak, and the maximum vertical-slip component was about 12 feet at Bell Flat. Most of the faults are at or near the alluvium-bedrock contact. A tectonic origin is proposed for these faults, however, since most of the faults have segments which cross bedrock or follow prehistoric scarps in alluvium. Dip-slip displacements were prevalent in the northern part of the area, and diagonal-slip or even strike-slip displacements characterized the southern part. The four main types of fault structure are herein defined as simple, subsidence, gravity-graben, and longitudinal step-fault types. The origin and nature of each type is discussed. Measurement of dip-slip components of displacement is complicated by the nature of these structures and earthfalls. In general, the scarp height is greater than the dip-slip component or throw. Comparison of geodetic data with field geologic data shows that the field geologist can, with care, measure fault displacements accurately, even across complex fault structures.

152 citations

Journal ArticleDOI
TL;DR: In this article, the authors used deformed marker surfaces to define the three-dimensional deformation field associated with their surface expression and to map displacement and length on ∼40 fault segments.

152 citations

Journal ArticleDOI
TL;DR: In this article, the L'Aquila and Campotosto faults are modeled as planar segments with different dips along depth rather than a smoothly curving single fault surface.
Abstract: [1] On 6 April (01:32 UTC) 2009 a MW 6.1 normal faulting earthquake struck the axial area of the Abruzzo region in central Italy. We study the geometry of fault segments using high resolution foreshock and aftershock locations. Two main SW dipping segments, the L'Aquila and Campotosto faults, forming an en echelon system 40 km long (NW trending). The 16 km long L'Aquila fault shows a planar geometry with constant dip (∼48°) through the entire upper crust down to 10 km depth. The Campotosto fault activated by three events with 5.0 ≤ MW ≤ 5.2 shows a striking listric geometry, composed by planar segments with different dips along depth rather than a smoothly curving single fault surface. The investigation of the spatiotemporal evolution of foreshock activity within the crustal volume where the subsequent L'Aquila main shock nucleated allows us to image the progressive activation of the main fault plane. From the beginning of 2009 the foreshocks activated the deepest portion of the fault until a week before the main shock, when the largest foreshock (MW 4.0) triggered a minor antithetic segment. Seismicity jumped back to the main plane a few hours before the main shock. Secondary synthetic and antithetic fault segments are present both on the hanging and footwall of the system. The stress tensor obtained by inverting focal mechanisms of the largest events reveals a NE trending extension and the majority of the aftershocks are kinematically consistent. Deviations from the dominant extensional strain pattern are observed for those earthquakes activating minor structures.

152 citations

Journal ArticleDOI
TL;DR: Mazzini et al. as mentioned in this paper investigated and understand the mechanisms responsible for the formation of piercement structures in sedimentary basins and the role of strike-slip faulting as a triggering mechanism for fluidization.

151 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