Fault (geology)

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

U-Pb geochronology of calcite-mineralized faults: Absolute timing of rift-related fault events on the northeast Atlantic margin

Abstract: Constraining the timing of brittle faulting is critical in understanding crustal deformation and fluid flow, but many regional-scale fault systems lack readily available techniques to provide absolute chronological information. Calcite mineralization occurs in crustal faults in many geological settings and can be suitable for U-Pb geochronology. This application has remained underutilized because traditional bulk dissolution techniques require uncommonly high U concentration. Because U and Pb are distributed heterogeneously throughout calcite crystals, high-spatial-resolution sampling techniques can target domains with high U and variable U/Pb ratios. Here we present a novel application of in-situ laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) to basaltic fault rock geochronology in the Faroe Islands, northeast Atlantic margin. Faults that are kinematically linked to deformation associated with continental break-up were targeted. Acquired ages for fault events range from mid-Eocene to mid-Miocene and are therefore consistently younger than the regional early Eocene onset of ocean spreading, highlighting protracted brittle deformation within the newly developed continental margin. Calcite geochronology from LA-ICP-MS U-Pb analysis represents an important and novel method to constrain the absolute timing of fault and fluid-flow events.

Working models for spatial distribution and level of Mars' seismicity

Abstract: [1] We present synthetic catalogs of Mars quakes, intended to be used for performance assessments of future seismic networks on the planet. We have compiled a new inventory of compressional and extensional tectonic faults for the planet Mars, comprising 8500 faults with a total length of 680,000 km. The faults were mapped on the basis of Mars Orbiting Laser Altimeter (MOLA) shaded relief. Hence we expect to have assembled a homogeneous data set, not biased by illumination and viewing conditions of image data. Updated models of Martian crater statistics and geological maps were used to assign new maximum ages to all faults. On the basis of the fault catalog, spatial distributions of seismicity were simulated, using assumptions on the available annual seismic moment budget, the moment-frequency relationship, and a relation between rupture length and released moment. We have constructed five different models of Martian seismicity, predicting an annual moment release between 3.42 × 1016 Nm and 4.78 × 1018 Nm and up to 572 events with magnitudes greater than 4 per year as upper limit end-member case. Most events are expected on the Tharsis shield, but minor seismic centers are expected south of Hellas and north of Utopia Planitia.

Faults and fault properties in hydrocarbon flow models

Abstract: Geofluids (2010) 10, 94–113 Abstract The petroleum industry uses subsurface flow models for two principal purposes: to model the flow of hydrocarbons into traps over geological time, and to simulate the production of hydrocarbon from reservoirs over periods of decades or less. Faults, which are three-dimensional volumes, are approximated in both modelling applications as planar membranes onto which predictions of the most important fault-related flow properties are mapped. Faults in porous clastic reservoirs are generally baffles or barriers to flow and the relevant flow properties are therefore very different to those which are important in conductive fracture flow systems. A critical review and discussion is offered on the work-flows used to predict and model capillary threshold pressure for exploration fault seal analysis and fault transmissibility multipliers for production simulation, and of the data from which the predictions derive. New flow simulation models confirm that failure of intra-reservoir sealing faults can occur during a reservoir depressurization via a water-drive mechanism, but contrary to anecdotal reports, published examples of production-induced seal failure are elusive. Ignoring the three-dimensional structure of fault zones can sometimes have a significant influence on production-related flow, and a series of models illustrating flow associated with relay zones are discussed.

Stress, fluid pressure and structural permeability in seismogenic crust, North Island, New Zealand

Abstract: SUMMARY Stress and fluid-pressure conditions within seismogenic crust are compared for two subparallel belts of active deformation and fluid redistribution associated with the obliquely convergent Pacific‐Australia plate boundary in the North Island of New Zealand. Whereas seismic activity on extensional normal faults in the arc-backarc Taupo volcanic zone is restricted to <8 km depth in a high heat-flow, near-hydrostatic fluid-pressure regime undergoing vigorous hydrothermal convection, rupturing along the thrust interface of the contractional Hikurangi subduction margin and in its hangingwall extends to ∼25 km depth in crust with fluids overpressured towards lithostatic values. The contrast in fluid-pressure levels stems partly from the abundance of low-permeability mudrocks in the forearc and partly from superior containment of overpressures by a compressional thrust-fault regime. Maximum supportable levels of differential stress and fluid pressure are critically interdependent in the overpressured regime of the Hikurangi subduction margin. Frictional instability leading to fault rupture in such settings may be triggered by increasing fluid pressure as well as by accumulating shear stress, so that nucleation and recurrence of earthquake ruptures are likely to be affected by cycling of fluid pressure through fault-valve action as well as by stress accumulation. Coupling across the subduction interface is also likely to be highly sensitive to the degree of overpressuring. Different factors are responsible for the localization of active deformation within the two crustal seismic belts. Within the magmatically active Taupo volcanic zone, thermal weakening is clearly responsible for concentrating seismicity and deformation with respect to the surrounding crust. However, in the hangingwall of the Hikurangi subduction margin, where heat flow has been reduced by subduction refrigeration and frictional interaction extends to ∼25 km depth, relative weakening arises principally from reduction of frictional resistance by fluid overpressuring.