Fault (geology)

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

Listric faulting, sedimentation, and morphological evolution of the Quaternary eastern Corinth rift, Greece: First stages of continental rifting

Abstract: The 30-km-wide Corinth rift is one of a series of west-northwest-trending Quaternary grabens in western Greece. In the north, a major listric fault marks the southern edge of a deep asymmetric graben filled by the sea.The footwall of this fault, which forms the southern part of the rift, has experienced epeirogenic uplift and 18% Quaternary extension along smaller listric faults. Rates of motion are determined by offsets in Quaternary rift-filling sediments. The uplift and listric extension of the southern part of the rift took place in the first two million years of rifting.This tectonic style occurs in other Greek Quaternary rifts, but comparable records have been destroyed by erosion in older rifts. Quaternary sediments exposed in the uplifted southern part of the rift comprise a northward-prograding deltaic sequence, the deposition of which continues today in the Gulf of Corinth. These Quaternary sediments are principally alluvial fan and coastal lacustrine conglomerates in the south, lacustrine Gilbert-type fan-delta conglomerates and marls in the center, and predominantly lacustrine marls overlain by thin marine or fluvial "caprock" in the north. The oldest marine "caprock" is mid-Pleistocene; this facies is generally transgressive over the lacustrine deltaic deposits. Mesoscopic structural features are unusually well developed in these sediments. Large listric faults are accommodated by minor synthetic or antithetic faults, rollover structures with counter faults, and low-dipping shear zones in the place where mesoscopic listric faults meet the decollement horizon. Some extension joints have been reactivated to form shear faults. The landscape on the uplifted southern part of the rift has flights of terraces previously interpreted as providing a detailed record of sea-level changes in the past 0.5 m.y. Most terraces result from fault disruption of the same delta-top surface, in places with marine caprock, that was also influenced by synsedimentary faulting. The marine caprock and associated alluvial facies are thin, and there is no evidence for river dissection due to lowered base level prior to the middle Pleistocene isotopic stage 6 (130-180 Ka); this indicates that marine highstands were only a little higher than normal lake level. In the late Pleistocene, lake levels dropped substantially during marine lowstands, leading to the dissection of the landscape and the deposition of thick alluvium during marine highstands. Caprock sediments preserve only an incomplete record of marine highstands.

Quaternary slip rate and geomorphology of the Alpine fault: Implications for kinematics and seismic hazard in southwest New Zealand

Abstract: Glacial landforms at 12 localities in 9 river valleys are offset by the southern end of the onshore Alpine fault Offsets cluster at ∼435, 1240, and 1850 m, consistent with evidence for glacial retreat at 18, 58, and 79 calendar ka The peak of an offset fluvial aggradation surface is correlated with the Last Glacial Maximum at 22 ka Displacement rates derived from features aged 18, 22, 58, and 79 cal ka are 242 ± 22, 232 ± 49, 214 ± 26, and 235 ± 27 mm/yr, respectively, with uncertainties at the 95% confidence level The joint probability, weighted mean, and arithmetic mean of all observations pooled by rank are 231 ± 15, 232 ± 14, and 231 ± 17 mm/yr, respectively We conclude that the mean surface displacement rate for this section of the Alpine fault is 231 mm/yr, with standard error in the range of 07–09 mm/yr The reduction in estimated long-term slip rate from 26 ± 6 mm/yr to 23 ± 2 mm/yr results in an increase in estimated hazard associated with faulting distributed across the rest of the plate boundary Model-dependent probabilities of Alpine fault rupture within the next 50 yr are in the range 14%–29% The 36 ± 3 mm/yr of total plate motion (NUVEL-1A) is partitioned into 23 ± 2 mm/yr of Alpine fault dextral strike slip, 12 ± 4 mm/yr of horizontal motion by clockwise block rotations and oblique dextral-reverse faulting up to 80 km southeast of the Alpine fault, and 5 ± 3 mm/yr of heave on reverse faults at the peripheries of the plate boundary

Present-day stresses, seismicity and Neogene-to-Recent tectonics of Australia’s ‘passive’ margins: intraplate deformation controlled by plate boundary forces

Abstract: Neogene-to-Recent deformation is widespread on and adjacent to Australia's 'passive' margins. Elevated historical seismic activity and relatively high levels of Neogene-to-Recent tectonic activity are recognized in the Flinders and Mount Lofty Ranges, the SE Australian Passive Margin, SW Western Australia and the North West Shelf. In all cases the orientation of palaeostresses inferred from Neogene-to-Recent structures is consistent with independent determinations of the orientation of the present-day stress field. Present-day stress orientations (and neotectonic palaeostress trends) vary across the Australian continent. Plate-scale stress modelling that incorporates the complex nature of the convergent plate boundary of the Indo-Australian Plate (with segments of continent-continent collision, con- tinent- arc collision and subduction) indicates that present-day stress orientations in the Australian continent are consistent with a first-order control by plate-boundary forces. The consistency between the present-day, plate-boundary-sourced stress orientations and the record of deformation deduced from neotectonic structures implicates plate boundary forces in the ongoing intraplate deformation of the Australian continent. Deformation rates inferred from seismicity and neotectonics (as high as 10 216 s 21 ) are faster than seismic strain rates in many other 'stable' intraplate regions, suggestive of unusually high stress levels imposed on the Australian intraplate environment from plate boundary interactions many thousands of kilometres distant. The spatial overlap of neotectonic structures and zones of concentrated historical seismicity with ancient fault zones and/or regions of enhanced crustal heat flow indicates that patterns of active deformation in Australia are in part, governed, by prior tectonic structuring and are also related to structural and thermal weakening of continental crust. Neogene-to-Recent intraplate deformation within the Australian continent has had profound and under-recognized effects on hydrocarbon occurrence, both by amplifying some hydrocarbon- hosting structures and by inducing leakage from pre-existing traps due to fault reactivation or tilting.

Interpreting the style of faulting and paleoseismicity associated with the 1897 Shillong, northeast India, earthquake: Implications for regional tectonism

Abstract: [1] The 1897 Shillong (Assam), northeast India, earthquake is considered to be one of the largest in the modern history Although Oldham's [1899] classic memoir on this event opened new vistas in observational seismology, many questions on its style of faulting remain unresolved Most previous studies considered this as a detachment earthquake that occurred on a gently north dipping fault, extending from the Himalayan front A recent model proposed an alternate geometry governed by high-angle faults to the north and south of the plateau, and it suggested that the 1897 earthquake occurred on a south dipping reverse fault, coinciding with the northern plateau margin In this paper, we explore the available database, together with the coseismic observations from the region, to further understand the nature of faulting The geophysical and geological data examined in this paper conform to a south dipping structure, but its location is inferred to be in the Brahmaputra basin, further north of the present plateau front Our analyses of paleoseismic data suggest a 1200-year interval between the 1897 event and its predecessor, and we identify the northern boundary fault as a major seismic source The Shillong Plateau bounded by major faults behaves as an independent tectonic entity, with its own style of faulting, seismic productivity, and hazard potential, distinct from the Himalayan thrust front, a point that provides fresh insight into the regional geodynamics

Relation between continental strike-slip earthquake segmentation and thickness of the crust

Abstract: [1] High-resolution maps of large continental strike-slip earthquake surface ruptures show that they are formed of fault segments. These segments are bounded by fault bends, step overs, or combinations of the two. The lowest limit in size for such segments may not be relevant in the understanding of earthquake mechanics, as it pertains to the granular properties of fault zones. The maximum limit in segment length, however, is important as it is directly relates to the maximum extent of seismic rupture. To measure the length of the segments, a new quantitative method based on piecewise linear fitting is developed and is used to automatically retrieve segments from earthquake rupture maps. Next, this approach is tested against a set of ten continental strike-slip earthquake ruptures derived from similar, high quality maps. The test suggests that segments have a maximum length of ∼18 km, independent of regional tectonic setting. Slip-inversions for earthquakes, based on seismological and/or geodetic data, most often are not unique and can show some variability even for one particular event. Some basic characteristics, however, such as total moment release or general source geometry, seem to persist that are relevant to earthquake mechanics. Measurements of the maximum horizontal extent of individual slip-patches derived from seismic source inversion for strike-slip ruptures show that their strike dimension does not increase infinitely with magnitude, but instead reaches a maximum value of ∼25 km. These two independent lines of observations, complemented by earlier data and analog experiments, suggest that it is the thickness of the seismogenic crust that controls the structural scaling of the length of seismic segments, and that it is independent of the ultimate size of individual earthquakes.