Discrete Fault Research Articles

A Qualitative Fault Isolation Approach for Parametric and Discrete Faults Using Structural Model Decomposition

With increasing complexity of engineering systems, fault diagnostics plays a significant role in ensuring that they operate safely. Such systems most often exhibit mixed discrete and continuous, i.e., hybrid, behavior, and may encounter both parametric faults (unexpected changes in system parameters) as well as discrete faults (unexpected changes in component modes). Diagnosis becomes computationally very complex due to the large number of possible system modes, and possible mode changes that occur near the point of fault occurrence. This paper presents a qualitative fault isolation framework for integrated diagnosis of both parametric and discrete faults in hybrid systems, based on structural model decomposition. Fault isolation is performed by analyzing the qualitative information of the residual deviations, and considering observation delay. The great advantage of structural model decomposition for this problem is that it essentially defines several smaller independent diagnosis problems that become more efficient to solve, and makes the overall diagnosis problem more scalable. To demonstrate and test the validity ofour approach, we use a hydraulic multi-tank system as the case study in simulation. Results illustrate that the approach is both efficient and scalable.

Structure and flow properties of syn-rift border faults: The interplay between fault damage and fault-related chemical alteration (Dombjerg Fault, Wollaston Forland, NE Greenland)

Structurally controlled, syn-rift, clastic depocentres are of economic interest as hydrocarbon reservoirs; understanding the structure of their bounding faults is of great relevance, e.g. in the assessment of fault-controlled hydrocarbon retention potential. Here we investigate the structure of the Dombjerg Fault Zone (Wollaston Forland, NE Greenland), a syn-rift border fault that juxtaposes syn-rift deep-water hanging-wall clastics against a footwall of crystalline basement. A series of discrete fault strands characterize the central fault zone, where discrete slip surfaces, fault rock assemblages and extreme fracturing are common. A chemical alteration zone (CAZ) of fault-related calcite cementation envelops the fault and places strong controls on the style of deformation, particularly in the hanging-wall. The hanging-wall damage zone includes faults, joints, veins and, outside the CAZ, disaggregation deformation bands. Footwall deformation includes faults, joints and veins. Our observations suggest that the CAZ formed during early-stage fault slip and imparted a mechanical control on later fault-related deformation. This study thus gives new insights to the structure of an exposed basin-bounding fault and highlights a spatiotemporal interplay between fault damage and chemical alteration, the latter of which is often underreported in fault studies. To better elucidate the structure, evolution and flow properties of faults (outcrop or subsurface), both fault damage and fault-related chemical alteration must be considered.

The role of gravitational collapse in controlling the evolution of crestal fault systems (Espírito Santo Basin, SE Brazil)

A high-quality 3D seismic volume from offshore Espírito Santo Basin (SE Brazil) is used to assess the importance of gravitational collapse to the formation of crestal faults above salt structures. A crestal fault system is imaged in detail using seismic attributes such as curvature and variance, which are later complemented by analyses of throw vs. distance (T-D) and throw vs. depth (T-Z). In the study area, crestal faults comprise closely spaced arrays and are bounded by large listric faults, herein called border faults. Two episodes of growth are identified in two opposite-dipping fault families separated by a transverse accommodation zone. Statistical analyses for eighty-four (84) faults show that fault spacing is < 250 m, with border faults showing the larger throw values. Fault throw varies between 8 ms and 80 ms two-way time for crestal faults, and 60–80 ms two-way time for border faults. Fault length varies between ∼410 m and 1750 m, with border faults ranging from 1250 m to 1750 m. This work shows that border faults accommodated most of the strain associated with salt growth and collapse. The growth history of crestal faults favours an isolated fault propagation model with fault segment linkage being associated with the lateral propagation of discrete fault segments. Importantly, two episodes of fault growth are identified as synchronous to two phases of seafloor erosion, rendering local unconformities as competent markers of fault reactivation at a local scale. This paper has crucial implications for the understanding of fault growth as a means to assess drilling risk and oil and gas migration on continental margins. As a corollary, this work demonstrates that: 1) a certain degree of spatial organisation occurs in crestal fault systems; 2) transverse accommodation zones can form regions in which fault propagation is enhanced and regional dips of faults change in 4D.

Complex events in a fault model with interacting asperities

The dynamics of a fault with heterogeneous friction is studied by employing a discrete fault model with two asperities of different strengths. The average values of stress, friction and slip on each asperity are considered and the state of the fault is described by the slip deficits of the asperities as functions of time. The fault has three different slipping modes, corresponding to the asperities slipping one at a time or simultaneously. Any seismic event produced by the fault is a sequence of n slipping modes. According to initial conditions, seismic events can be different sequences of slipping modes, implying different moment rates and seismic moments. Each event can be represented geometrically in the state space by an orbit that is the union of n damped Lissajous curves. We focus our interest on events that are sequences of two or more slipping modes: they show a complex stress interchange between the asperities and a complex temporal pattern of slip rate. The initial stress distribution producing these events is not uniform on the fault. We calculate the stress drop, the moment rate and the frequency spectrum of the events, showing how these quantities depend on initial conditions. These events have the greatest seismic moments that can be produced by fault slip. As an example, we model the moment rate of the 1992 Landers, California, earthquake that can be described as the consecutive failure of two asperities, one of which has a double strength than the other, and evaluate the evolution of stress distribution on the fault during the event.

Incorporation of deformation band fault damage zones in reservoir models

Fault damage zones in porous sandstones commonly exhibit networks of deformation bands reflecting crushing and reorganization of grains associated with small-scale, localized displacement. Deformation bands introduce anisotropic, order-of-magnitude reduction of effective permeability, which will affect fluid flow in reservoir rocks. We here present a method for incorporating these features in industrial-type reservoir models. The method involves the use of a three-dimensional fault zone grid generation technique that allows property modeling on a discrete high-resolution fault zone grid without refining the entire reservoir model. Deformation band data from 106 outcrop scan lines of fault damage zones were classified into discrete fault facies defined according to deformation band density. The distributional pattern of fault facies in the data exhibits recurrent spatial relationships, which could be reproduced using truncated Gaussian simulation in the modeling process. The frequency distribution of deformation band density for each facies was analyzed, and average density values were assigned to each facies for calculating cell permeability. Permeability anisotropy was handled by approximating the relationship between deformation band densities in different directions based on published high-resolution fault zone maps and cross sections. Fluid-flow simulations were carried out on several damage zones models, and results were benchmarked against models with conventional fault rendering without damage zones. Simulation results show that flow paths, remaining oil distribution, and reservoir responses in models incorporating damage zones deviate from models employing conventional fault representation without damage zones, and these differences increase as deformation band permeability decreases.

Seismic attribute detection of faults and fluid pathways within an active strike-slip shear zone: New insights from high-resolution 3D P-Cable™ seismic data along the Hosgri Fault, offshore California

Poststack data conditioning and neural-network seismic attribute workflows are used to detect and visualize faulting and fluid migration pathways within a [Formula: see text] 3D P-Cable™ seismic volume located along the Hosgri Fault Zone offshore central California. The high-resolution 3D volume used in this study was collected in 2012 as part of Pacific Gas and Electric’s Central California Seismic Imaging Project. Three-dimensional seismic reflection data were acquired using a triple-plate boomer source (1.75 kJ) and a short-offset, 14-streamer, P-Cable system. The high-resolution seismic data were processed into a prestack time-migrated 3D volume and publically released in 2014. Postprocessing, we employed dip-steering (dip and azimuth) and structural filtering to enhance laterally continuous events and remove random noise and acquisition artifacts. In addition, the structural filtering was used to enhance laterally continuous edges, such as faults. Following data conditioning, neural-network based meta-attribute workflows were used to detect and visualize faults and probable fluid-migration pathways within the 3D seismic volume. The workflow used in this study clearly illustrates the utility of advanced attribute analysis applied to high-resolution 3D P-Cable data. For example, results from the fault attribute workflow reveal a network of splayed and convergent fault strands within an approximately 1.3 km wide shear zone that is characterized by distinctive sections of transpressional and transtensional dominance. Neural-network chimney attribute calculations indicate that fluids are concentrated along discrete faults in the transtensional zones, but appear to be more broadly distributed amongst fault bounded anticlines and structurally controlled traps in the transpressional zones. These results provide high-resolution, 3D constraints on the relationships between strike-slip fault mechanics, substrate deformation, and fluid migration along an active fault system offshore central California.

震源特性の不確定性が地震動強さや建物応答に及ぼす影響

In this study, structural response analyses with ground-motion time histories are conducted for an RC structure. These ground motions incorporate the uncertainties of macro-scopic and micro-scopic seismic-source characteristics. The purpose of this study is to examine the relationship between the uncertainties of seismic-source characteristics, seismic intensities and structural responses. As a result, it is clarified that seismic moment M0, stress drop Δσ and Q-value coefficient CQc positively correlate with seismic intensities and maximum structural responses. It can also be seen that M0 highly correlates with velocity, displacement and energy indices of seismic intensities, and that Δσ and CQc highly correlate with acceleration related indices. The reasons are discussed referring to the effect of the varieties of source characteristics on the ground-motion Fourier spectra from the discrete faults. The asperity location aspX negatively correlates with seismic intensities and with maximum structural responses because of the location between the reference site and faults. It is also detected that seismic intensities, M.S.I. and Ajma, can be better as hazard indices because the variations of structural responses along these indices are relatively smaller than those along other intensities.

Online Monitoring and Fault Diagnosis of Hybrid Systems Using Switched Dynamic Bayesian Networks

&#x0D; &#x0D; &#x0D; Modern real-world engineering systems typically have hybrid dynamic behaviors that can be modeled by continuous behaviors with discrete mode transitions. These complex systems present many significant challenges for online monitoring and diagnosis, including tracking system behavior, dealing with noisy measurements and disturbances, and diagnosing different types of faults. In this paper, we propose an integrated model-based diagnosis approach that extends the traditional Dynamic Bayesian Network-based particle filter approach for tracking continuous system dynamics. A novel mode diagnoser is presented that discriminates between residuals generated by inaccurate system tracking, discrete faults, and parametric faults. An extended quantitative fault isolation and identification scheme is combined with a qualitative fault isolation scheme to identify the abrupt parametric faults. We demonstrate the effectiveness of our approach by applying it to Reverse Osmosis (RO) subsystem of the Water Recovery System (WRS) developed at the NASA Johnson Space Center for long duration human missions.&#x0D; &#x0D; &#x0D;

Paleoseismology of the Mount Narryer fault zone, Western Australia: A multistrand intraplate fault system

Our paleoseismological study of faults and fault-related folds comprising the Mount Narryer fault zone reveals a mid- to late Quaternary history of repeated morphogenic earthquakes that have influenced the planform and course of the Murchison, Roderick, and Sanford Rivers, Western Australia. The dominant style of deformation involves folding of near-surface sediments overlying discrete basement faults. Carbon-14, optically stimulated luminescence, and in situ–produced 10 Be constrain the timing of the events and late Quaternary slip rates associated with fault propagation folds in tectonically uplifted and deformed alluvial channel deposits. A flight of five inset fluvial terraces is preserved where the Murchison River flows across the Roderick River fault. These terraces, which we infer to be coseismic, are consistent with at least four late Quaternary seismic events on the order of moment magnitude (M w ) 7.1 within the last ~240 k.y. Secondary shears expressed on the folds indicate a component of dextral strike-slip displacement. Quaternary slip rates on the underlying faults range from 0.01 to 0.07 mm yr –1 , with a total slip rate for the zone between 0.04 and 0.11 mm yr –1 . These rates are intermediate to those in the adjacent Mesozoic basin (>0.1 mm yr –1 ) and Precambrian craton ( –1 ) and so provide insight into how tectonic strain is partitioned and transferred across a craton margin.

Late stage exhumation of HP metamorphic rocks, progressive localization of strain, and changes in transport direction, Sambagawa belt, Japan

New geologic mapping delimits major structures associated with the later stages of exhumation of high-pressure (HP) metamorphic rocks of the Sambagawa belt of central Shikoku. The main sets of structures define an inclined N-dipping wedge, bounded by S-vergent thrust faults below and N-vergent normal faults above. Such faults bound every metamorphic mineral zone of the Sambagawa belt. Faults also occur within metamorphic mineral zones, such as the Asemigawa detachment, which is entirely within the oligoclase–biotite zone, the highest-grade metamorphic zone. This fault is the structurally lowest of the N-vergent normal faults. These D2 structures accommodate the exhumation of the higher-grade rocks relative to the lower-grade rocks within the Sambagawa belt, rather than relative to units bounding the belt, so they are termed an “internal” extrusional wedge. The extrusional wedge is truncated to the east against footwall chlorite zone rocks by the Hamegano out-of-sequence thrust (OOST). The OOST divides the traditional chlorite zone into an upper unit consisting of varicolored schist (L tectonite), and a lower unit consisting of regionally extensive pelitic schist. To the north, the metamorphic mineral zones are stacked over the OOST, forming the Tomisato duplex, and these structures are further modified by the Oboke anticline and Tsuneyama syncline. The evolution of exhumation structures of the Sambagawa suggests progressive localization of strain as exhumation proceeded, as well as a change in movement direction from D1 oblique (orogen-subparallel) exhumation to the D2 structures with dip-parallel (orogen-normal) transport that we describe in detail. The evolution of exhumation structures in the Sambagawa belt differs from that of the HP rocks of the Franciscan Complex of California in that the exhumation of the latter is accommodated entirely by discrete faults and the Franciscan lacks internal normal faults. The internal extrusional wedge structure of the Sambagawa HP rocks resembles that of HP rocks of Leti Island of eastern Indonesia.

Fault detection and isolation for a multi-cellular converter based on sliding mode observer

This paper presents a model-based approach for the fault diagnosis of three-cell power converters. The goal is to design a fault detection and isolation (FDI) scheme which diagnoses parametric and discrete faults. Parametric faults are characterized by abnormal changes in the capacitor value whereas a discrete fault affects a switching element and is characterized by an abrupt deviation of the dynamics of the system. The combined continuous and discrete diagnosers are used to detect and isolate the discrete and the parametric faults. The discrete diagnoser is based on an appropriate decomposition of the hybrid model of the three-cell converter. The continuous diagnoser is based on a set of residuals which enable a comparison between the measured and estimated values of each continuous variable. Some experiments are shown to prove the effectiveness of the proposed scheme.

Structure and lithology of the Japan Trench subduction plate boundary fault

The 2011 Mw9.0 Tohoku-oki earthquake ruptured to the trench with maximum coseismic slip located on the shallow portion of the plate boundary fault. To investigate the conditions and physical processes that promoted slip to the trench, Integrated Ocean Drilling Program Expedition 343/343T sailed 1 year after the earthquake and drilled into the plate boundary ∼7 km landward of the trench, in the region of maximum slip. Core analyses show that the plate boundary décollement is localized onto an interval of smectite-rich, pelagic clay. Subsidiary structures are present in both the upper and lower plates, which define a fault zone ∼5–15m thick. Fault rocks recovered from within the clay-rich interval contain a pervasive scaly fabric defined by anastomosing, polished, and lineated surfaces with two predominant orientations. The scaly fabric is crosscut in several places by discrete contacts across which the scaly fabric is truncated and rotated, or different rocks are juxtaposed. These contacts are inferred to be faults. The plate boundary décollement therefore contains structures resulting from both distributed and localized deformation. We infer that the formation of both of these types of structures is controlled by the frictional properties of the clay: the distributed scaly fabric formed at low strain rates associated with velocity-strengthening frictional behavior, and the localized faults formed at high strain rates characterized by velocity-weakening behavior. The presence of multiple discrete faults resulting from seismic slip within the décollement suggests that rupture to the trench may be characteristic of this margin.

The A-to-Z of faulting in the offshore Arabian Gulf: Arabian trend structures overprinted by a Zagros wrench-fault assemblage

Abstract.Most major fields in the northeastern area of Saudi Arabia and Kuwait are anticlinal structures developed above north-northeast–south-southwest-trending basement lineaments. Based on structural interpretation of 3D seismic data sets, the fault pattern over one such field in the offshore Arabian Gulf of Kuwait and Saudi Arabia was analyzed in detail and integrated into the regional tectonic framework. Two discrete fault sets were identified. First, a system of Cretaceous extensional block faulting was observed that is parallel to and associated with folding over the basement structure. Second, a complex wrench-fault assemblage was identified associated with a Palaeogene dextral couple across the Zagros suture, which overprinted the inherited structural fabric. Convex-upward, Zagros-parallel flower structures were interpreted along with coeval synthetic and antithetic strike-slip fault systems. The interpretation of two discrete faults sets was then applied to an adjacent field that proved to have experienced a more complex tectonic history. Integration of the seismic fault interpretation into the regional tectonic history provided a robust framework that enhanced the understanding of the fault pattern and the structural interpretation of a nearby more complex field.

Iterative hybrid causal model based diagnosis: Application to automotive embedded functions

This paper addresses off-line diagnosis of embedded functions, such as that made in workshops by the technicians. The diagnosis problem expresses as the determination of a proper sequence of tests and measures at available control points, which would lead to greedily localize the fault quickly and at the lowest cost. Whereas anticipated discrete faults can be properly addressed by fault dictionary methods based on simulation, a consistency based method designed for hybrid systems is proposed to address parametric faults and non-anticipated faults. This method uses those same inputs as the fault dictionary method and the only additional information is the structure of the reference models in the form of a causal graph and the interpretation of the simulation results into qualitative values and events. The consistency based diagnosis method is combined with a test selection procedure to produce an original iterative diagnosis method for hybrid systems that reduces diagnosis ambiguity at each iteration.The method is illustrated in the automotive domain with a real case study consisting in the electronic function commanding the rear windscreen wiper of a car.

Decentralized Approach for Fault Diagnosis of Three Cell Converters

&#x0D; &#x0D; &#x0D; In this paper, an approach for fault diagnosis of hybrid dynamic systems (HDS), in particular discretely controlled continuous system, is proposed. The goal is to construct a decentralized diagnosis structure, able to diagnose parametric and discrete faults. This approach considers the system as composed of a set of interacted hybrid components (HCs). Each HC is composed of a discrete component (Dc), e.g. on/off switches, with the continuous components (Ccs), e.g. capacitors, whose continuous dynamic behavior is influenced by the Dc discrete states. A local hybrid diagnosis module, called diagnoser, is associated to each HC in order to diagnose the faults occurring in this HC. In order to take into account the interactions between the different HCs, local diagnosis decisions are merged using a coordinator. The latter issues a final decision about the origin of the fault and identifies its parameters. The advantage of the proposed approach is that local hybrid diagnosers as well as the coordinator are built using local models. The proposed approach is applied to achieve the decentralized diagnosis of discrete and parametric faults of power electronic three-cell converters.&#x0D; &#x0D; &#x0D;

Robust dead reckoning system for mobile robots based on particle filter and raw range scan.

Robust dead reckoning is a complicated problem for wheeled mobile robots (WMRs), where the robots are faulty, such as the sticking of sensors or the slippage of wheels, for the discrete fault models and the continuous states have to be estimated simultaneously to reach a reliable fault diagnosis and accurate dead reckoning. Particle filters are one of the most promising approaches to handle hybrid system estimation problems, and they have also been widely used in many WMRs applications, such as pose tracking, SLAM, video tracking, fault identification, etc. In this paper, the readings of a laser range finder, which may be also interfered with by noises, are used to reach accurate dead reckoning. The main contribution is that a systematic method to implement fault diagnosis and dead reckoning in a particle filter framework concurrently is proposed. Firstly, the perception model of a laser range finder is given, where the raw scan may be faulty. Secondly, the kinematics of the normal model and different fault models for WMRs are given. Thirdly, the particle filter for fault diagnosis and dead reckoning is discussed. At last, experiments and analyses are reported to show the accuracy and efficiency of the presented method.

Circle Equation-Based Fault Modeling Method for Linear Analog Circuits

Owing to the lack of feasible fault modeling method, hard (open and short) faults and discrete parameter faults are still the mostly used fault models. These models cannot characterize all soft faults occurring in analog circuits because the parameters of analog element are continuous. To address this concern, a new circle equation-based modeling method is developed. In a linear analog circuit, we prove that the real and imaginary parts of voltage phasor at any test node satisfy circle equation with respect to any network element. The equation is independent from the value of element to be modeled, and uniquely determined by its location and the nominal values of the remaining elements in the circuit under test. Hence, the circle equation can model any continuous parameter shifting (soft) or hard fault occurs to linear and piecewise linear circuits. Three points are sufficient to determine a circle; therefore, only three simulations corresponding to three distinct faulty parameters are enough to model all parameter shifting faults that occur in any network element. The effectiveness of the proposed approach is verified by simulation and comparison with other modeling methods.

Combined analysis of faults and deformation bands reveals the Cenozoic structural evolution of the southern Bükk foreland (Hungary)

A combination of fault slip data and deformation band analysis allows the separation of 8 deformation phases (D1–D8) in the southern foreland of the Bükk Mts., NE Hungary. The newly defined D1 phase is characterised by NE–SW compression which is hard to integrate into the Cenozoic evolution of the area. The D2a is also a new stress state which was a NE–SW syn-sedimentary extension of Late Oligocene age. The coeval D2b stress state is characterised by NW–SE compression and was responsible for the (partly syn-sedimentary) tilting and erosion of the Oligocene sediments during Late Oligocene to earliest Miocene. D3 corresponds to E–W compression and perpendicular extension. It was followed by NE–SW (D4) and WNW–ESE extension (D5) which corresponds to the main rifting phases of the Pannonian Basin system from the late Early to Mid-Miocene (17.3–15Ma and 15–11.6Ma, respectively). It was interrupted by a short inversion (D6) of NE–SW to ENE–WSW compression at latest Mid-Miocene to earliest Late Miocene. Extension and major tilting were renewed in the early Late Miocene (D7). D8 shows NW–SE compression during latest Miocene to Pliocene when the Bükk Mts. started to be uplifted.Deformation bands were formed during several of the established tectonic phases. Combined analysis of deformation bands and fault slip data permitted the unraveling of the evolution of deformation bands in connection with deformation mechanism, burial depth and cumulative displacement. We suggest that the less destructive type of deformation bands is the oldest ones, and were formed at the shallowest burial and accumulated the smallest total displacement. The more cataclastic the deformation bands are, the greater the total displacement and deeper burial depth that can be observed. With progressive burial and/or displacement, deformation bands evolved into discrete fault slip surface.

Application of an ANN-based methodology for road surface condition identification on mining vehicles and roads

An artificial neural networks-based methodology for the identification of road surface condition was applied to two different vehicles in their normal operating environments at two mining sites. An ultra-heavy haul truck used for hauling operations in surface mining and a small utility underground mine vehicle were utilised in the current investigation. Unlike previous studies where numerical models were available and road surfaces were accurately profiled with profilometers, in this study, that was not the case in order to replicate the real mine road management situation. The results show that the methodology performed very well in reconstructing discrete faults such as bumps, depressions or potholes but, owing to the inevitable randomness of the testing conditions, these conditions could not fit the fine undulations present on the arbitrary random rough surface. These are better represented by the spectral displacement densities of the road surfaces. Accordingly, the proposed methodology can be applied to road condition identification in two ways: firstly, by detecting, locating and quantifying any existing discrete road faults/features, and secondly, by identifying the general level of the road’s surface roughness.

Landslide triggers along volcanic rock slopes in eastern Sicily (Italy)

A new dataset of landslides, occurred in a tectonically active region, has been analysed in order to understand the causes of the slope instability. The landslides we have dealt with took place along the volcanic rock cliff of S. Caterina and S. Maria La Scala villages (eastern Sicily, Italy), a densely inhabited area located on the eastern margin of Mt. Etna, where some seismogenic faults, locally named Timpe system, slip during moderate local earthquakes and also move with aseismic creep mechanisms. The results show that landslides are triggered by heavy rainfalls, earthquakes and creep fault episodes. Indeed, they occur along discrete fault segments, exhibiting a combination of both brittle failure, indicated by the earthquake occurrence, and aseismic creep events. The analysis of seismicity occurred on the Timpe fault system has shown that the active Acireale fault, in its southernmost segment, is subject to an aseismic sliding, which increases after the stick–slip motion in the nearby faults. Therefore, aseismic creep seems to concur in the predisposition of a rock to fail, since strains can increase the jointing of rock masses leading to a modification in the slope stability. Understanding the factors concurring to the slope instability is a useful tool for future assessments of the landslide hazard in densely settled areas, located on a volcanic edifice, such as Etna that is slowly sliding seawards, and where active faults, seismicity and heavy rains affect the deeply fractured slopes.