Fault Offsets Research Articles

A Fault Tolerance Method for Multiple Current Sensor Offset Faults in Grid-Connected Inverters

Three-phase grid-connected inverters have been widely used in the distributed generation system, and the current sensor has been applied in closed-loop control in inverters. When the current sensor offset faults occurs, partial fault features of multiple current sensors disappear from the closed-loop control grid-connected system, which leads to difficulties for fault diagnostics and fault-tolerant control. This paper proposes a fault tolerance method based on average current compensation mode to eliminate these adverse effects of fault features. The average current compensation mode compensates the average of the three-phase current to the αβ axis current to realize the fault feature reconstruction of the current sensor. The mode does not affect the normal condition of the system. Then, the data-driven method is used for fault diagnosis, and the corresponding fault tolerant control model is selected according to the diagnosis results. Finally, the experimental results show that the proposed strategy has a good fault tolerance control performance and can improve the fault feature discrimination and diagnostic accuracy.

Seismic mapping of shallow bedrock shelves in the hanging wall of the Wasatch fault

The Wasatch fault (WF) has been the subject of intensive study. Adjacent to a large and growing urban corridor, it poses a distinct seismic hazard for ∼2.5 million residents who live on its hanging wall, and has numerous Quaternary scarps and produced a M5.7 quake in March of 2020. Thus, the shallow architecture of the fault is important for understanding its earthquake hazards.Prior work has revealed shallow bedrock shelves in the hanging wall near the fault. To detect and image these shelves, we have employed the HVSR method (horizontal-to-vertical spectral ratio) at three locations along and across the WF. This method is powerful in that data can be collected rapidly in an urban setting. However, this method requires knowledge of the Vs of sediment overlying bedrock in order to estimate bedrock depth. We employed the MASW (multichannel-analysis of surface waves) method to obtain the characteristic Vs of sediment overlying bedrock.At Corner Canyon in Draper, Utah, Lake Bonneville sands and gravels overlie intrusive rocks of the Little Cottonwood Stock. Fault offsets inferred from HVSR correlate to mapped scarps. At Traverse Ridge, an HVSR profile co-located to a prior seismic reflection profile also detected shallow bedrock beneath alluvial fan sediment, including a graben system. However, at this site the geology is more complex. Fan sediment is underlain by altered volcanic rocks with subjacent quartzite. The HVSR method detected and characterized these boundaries.A majority of data were collected across the WF in the vicinity of Rock Canyon, Utah in order to create a 3D surface of the bedrock shelf. This area is heavily developed, but with numerous mapped scarps. A 3D model of the bedrock shelf indicates that it is broad, >1 km from the main trace of the WF. This width was not previously known. The HVSR results conform to mapped fault offsets, but also reveal a large, buried (and previously unknown) graben.One main finding of this study is that HVSR is a useful tool for mapping the shallow architecture of bedrock shelves in the hanging wall of normal faults, as long as a reasonable estimate of the Vs of sediment overlying bedrock can be made. Mapping can be accomplished rapidly in uneven topography or in urban settings as the instrumental footprint is very small. A second main finding is that large normal faults may commonly have concealed bedrock shelves. These shelves may affect engineering inputs like Vs30. However, they may also have other unanticipated effects on the nature of ground shaking, perhaps due to the trapping of energy or reverberation between the ground surface, bedrock shelf, and bedrock in the foot wall.

The formation of the 8˚20’ N seamount chain, east pacific rise

Near-axis seamounts provide a unique setting to investigate three-dimensional mantle processes associated with the formation of new oceanic crust and lithosphere. Here, we investigate the characteristics and evolution of the 8˚20’N Seamount Chain, a lineament of seamounts that extends ~ 175 km west of the East Pacific Rise (EPR) axis, just north of the fracture zone of the Siqueiros Transform Fault. Shipboard gravity, magnetic, and bathymetric data acquired in 2016 are utilized to constrain models of seamount emplacement and evolution. Geophysical observations indicate that these seamounts formed during four distinct episodes of volcanism coinciding with changes in regional plate motion that are also reflected in the development of intra-transform spreading centers (ITSCs) along the Siqueiros transform fault (Fornari et al. 1989; Pockalny et al. 1997). Although volcanism is divided into distinct segments, the magnetic data indicate continuous volcanic construction over long portions of the chain. Crustal thickness variations along the chain up to 0.75 km increase eastward, inferred from gravity measurements, suggest that plate reorganization has considerably impacted melt distribution in the area surrounding the Siqueiros-EPR ridge transform intersection. This appears to have resulted in increased volcanism and the formation of the 8˚20’N Seamounts. These findings indicate that melting processes in the mantle and subsequently the formation of new oceanic crust and lithosphere are highly sensitive to tectonic stress changes in the vicinity of fast-spreading transform fault offsets.

Intelligent Fault Detection in Hall-Effect Rotary Encoders for Industry 4.0 Applications

Sensors are the foundational components of any smart machine system and are invaluable in all modern technologies. Consequently, faults and errors in sensors can have a significant negative impact on the setup. Intelligent, lightweight, and accurate fault diagnosis and mitigation lie at the crux of modern industries. This study aimed to conceptualize a germane solution in the domain of fault detection, focusing on Hall-effect rotary encoders. Position monitoring through rotary encoders is essential to the safety and seamless functioning of industrial equipment such as lifts and hoists, and commercial systems such as automobiles. This work used multi-strategy learners to accurately diagnose quadrature and offset faults in Hall-effect rotary encoders. The obtained dataset was then run through a lightweight ensemble classifier to train a robust fault detection model. The complete mechanism was simulated through interconnected models simulated in a MATLAB Simulink™ environment. In real time, the developed fault detection algorithm was embedded in an FPGA controller and tested with a 1 kW PMSM drive system. The resulting system is computationally inexpensive and achieves an accuracy of 95.8%, making it a feasible solution for industrial implementation.

A Late Cenozoic Kinematic Model for Fault Motion Within Greater Cascadia

AbstractWidely accepted tectonic reconstructions indicate at least 100 km of coast‐parallel northwestward translation of the Sierra Nevada block of California and 15–20° clockwise rotation of most of Oregon since the current phase of Basin and Range extension began ∼17 Ma. These reconstructions require at least 100 km of convergence between the central Coast Range of Oregon and rigid North America in mainland British Columbia, yet there is little discussion of how such convergence might be distributed. This study offers a kinematic model of the distribution of such deformation, constrained by geodesy, paleomagnetism, and fault offsets in Nevada, California and Oregon. The model includes differential rotation across the thrust faults of the Yakima fold and thrust belt (YFTB), compressive right‐lateral faulting in the Washington Cascade Range, substantial thrust faulting within the Puget Lowland, and oroclinal bending and doming in the Olympic Mountains. Shortening across YTFB along 120°W longitude is modeled as 47 km, across Puget Lowland at 123°W (Olympia‐Bellingham) is 94 km, and total shortening between the central Oregon Coast Range and northern Washington (Corvallis‐Bellingham) is 125 km. Current motion of the coastal regions above the Cascadia subduction zone results from both permanent deformation of the continent and elastic coupling to the subducting plate. Permanent deformation in the model is based on extrapolating geodesy from east of 120°W or south of 40°N, indicating a very uniform convergence velocity with the Juan de Fuca plate for northernmost California and Oregon near 31 mm/yr at N61°E.

Re-visiting the structural and glacial history of the Shackleton Glacier region of the Transantarctic Mountains, Antarctica

ABSTRACT Only at Cape Surprise, central Transantarctic Mountains, is there exposed stratigraphic evidence for major offset along the range front, which marks a major boundary in Antarctica. Several faults parallel to the range front have been identified in the Devonian to Triassic Gondwana strata in the hinterland. Analysis of the stratigraphy based on field observations and the United States Geological Survey (USGS) aerial photographs, in conjunction with USGS topographic sheets and satellite-derived elevation measurements, suggests an array of faults with varying orientations and displacements. Fault offsets range up to an estimated 850 metres. No additional range-parallel faults have been identified and no clear pattern of faulting is evident in the hinterland of the frontal escarpment. Faulting may date from the time of slow uplift during the Cretaceous as well as the more rapid Cenozoic uplift of the range. Only a few faults in the hinterland can be allied with the fontal fault system. Cenozoic uplift and associated denudation was accompanied by glaciation of Antarctica, which is documented by Sirius Group strata. These deposits, which pre-date today’s polar landscape, are older than mid Miocene, and in part may date from the earliest stages of warm-based glaciation in the early Oligocene.

New Insights Into the Paleoseismic History of the Mae Hong Son Fault, Northern Thailand

The Mae Hong Son Fault (MHSF) is a north-trending active fault in northern Thailand. The largest earthquake ever recorded in Thailand occurred in February 1975 with a magnitude of 5.6 and was associated with the southern end of the MHSF. Paleoearthquake magnitudes, recurrence intervals, and slip rates for the MHSF are evaluated using the morphological characteristics of the MHSF aided with a 12.5-m-resolution digital elevation model (DEM) and using fault trenching. Morphotectonic analysis, including studies of offset streams, linear valleys, triangular facets, and fault scarps, helps illustrate dextral fault movements within the MHSF zone. Two separated N–S trending basins, the Mae Hong Son to the north and the Mae Sariang to the south, are present along the MHSF. Between these basins, fault displacements decrease toward the Khun Yuam area. Surface rupture length investigation from fault segments in both basins indicates maximum credible earthquake magnitudes between 5.8 and 6.3. Fault trenching and road-cut studies show that nine earthquakes occurred along the MHSF over the past ∼43 ka. Optically stimulated luminescence (OSL) dating help define the timing of the earthquakes to ∼43, ∼38, ∼33, ∼28, ∼23, ∼18, ∼13, ∼8, and ∼3 ka. The recurrence interval of earthquakes on the Mae Hong Son Fault is ∼5,000 years and the fault has a slip rate of ∼0.04–0.15 mm/a.

Continental-scale structural heritage from rift extension to postrift inversion: Implications for the central Brazilian Equatorial Margin evolution

The link between major basement anisotropies and basin evolution is crucial for understanding the role of tectonic inheritance on continental margins. However, it is still a matter of debate how and why it happens, especially in the Equatorial Atlantic, where the interplay between Precambrian fabric and the shearing of major oceanic fractures has been studied. Here, we investigate the offshore Ceará Basin and its basement in the central part of the Brazilian Equatorial Margin to (1) map basement anisotropies underneath marginal basins and show how Precambrian crustal domains influenced basin evolution; (2) determine the deformation style of reactivated basement faults; and (3) assess the interplay between reactivated faults and the oceanic Romanche Fracture Zone. The combined geological and geophysical data show that reactivation of NE-SW to ENE-WSW continental-scale ductile shear zones that acted as crustal weakness zones started in the Early Cretaceous under a normal stress field. Stress field inversion occurred in the Barremian during the continental breakup when the South American plate started to became an independent intraplate area under a strike-slip stress regimes. The shear zones arrest at the E-W-striking Romanche Fracture Zone, which marks the continental-oceanic boundary. The major fault offsets occurred along the Transbrasiliano Shear Zone, which represented a collisional boundary between paleocontinents in the Neoproterozoic. Fault reactivation also occurred in the eastern boundary of the Ceará Terrace marginal ridge along the Transbrasiliano Shear Zone, uplifted during tectonic inversion. We conclude that fault reactivation mainly occurred between contrasting Precambrian terrains separated by ductile shear zones. Additionally, the folds associated with the Romanche Fracture Zone were mainly generated along reactivated faults that affected syn- to postrift units on the Equatorial Margin.

The Arkalochori Mw = 5.9 Earthquake of 27 September 2021 Inside the Heraklion Basin: A Shallow, Blind Rupture Event Highlighting the Orthogonal Extension of Central Crete

A strong, shallow earthquake occurred near Heraklion (Crete, Greece) on 27 September 2021. The earthquake produced significant ground deformation in the vicinity of Arkalochori village but without any evidence for surface ruptures of primary origin. We used geodetic (InSAR and GNSS) data to map motions of the Earth’s surface that occurred during and shortly after the earthquake. A 14 cm subsidence of the GNSS station ARKL and a maximum of 19 cm distance from the SAR satellite were recorded. The measured surface displacements were used to constrain the rupture geometry and slip distribution at depth. Our best-fitting inversion model suggests that the rupture occurred on a 13 km-long planar normal fault striking N195° E dipping 55° to the northwest, with major slip occurring to the east and updip of the hypocentre. The fault tip is located 1.2 km beneath the surface. The maximum coseismic slip occurred in the uppermost crust, in the depth interval of 4–6 km. A decrease in the fault offsets toward the Earth’s surface is likely caused by an increased frictional resistance of the shallow layers to rapid coseismic slip. Satellite observations made in the first month after the earthquake detected no post-seismic deformation (i.e., below one fringe or 2.8 cm). The seismic fault may be identified with the Avli (Lagouta) segment of the NNE-SSW striking, west-dipping, 23 km-long neotectonic Kastelli Fault Zone (KFZ). Part of the rupture occurred along the Kastelli segment, indicating a fault segment linkage and a history of overlapping ruptures along KFZ. Based on geological data and footwall topography we estimate an average slip rate between 0.17–0.26 mm/yr for the KFZ. The Arkalochori earthquake is a paradigm example for the on-going extension of Heraklion basin (central Crete) in the WNW-ESE direction, which is almost orthogonal to the E-W Messara graben and other active faults along the south coast of Crete.

Analysis of Fault Classifiers to Detect the Faults and Node Failures in a Wireless Sensor Network

Technology evaluation in the electronics field leads to the great development of Wireless Sensor Networks (WSN) for a variety of applications. The sensor nodes are deployed in hazardous environments, and they are operated by isolated battery sources. Network connectivity is purely based on power availability, which impacts the network lifetime. Hence, power must be used wisely to prolong the network lifetime. The sensor nodes that fail due to power have to detect quickly to maintain the network. In a WSN, classifiers are used to detect the faults for checking the data generated by the sensor nodes. In this paper, six classifiers such as Support Vector Machine, Convolutional Neural Network, Multilayer Perceptron, Stochastic Gradient Descent, Random Forest and Probabilistic Neural Network have been taken for analysis. Six different faults (Offset fault, Gain fault, Stuck-at fault, Out of Bounds, Spike fault and Data loss) are injected in the data generated by the sensor nodes. The faulty data are checked by the classifiers. The simulation results show that the Random Forest detected more faults and it also outperformed all other classifiers in that category.

Deep Neural Network-Based Removal of a Decaying DC Offset in Less Than One Cycle for Digital Relaying

To make a correct decision during normal and transient states, the signal processing for relay protection must be completed and designated the correct task within the shortest given duration. This paper proposes to solve a dc offset fault current phasor with harmonics and noise based on a Deep Neural Network (DNN) autoencoder stack. The size of the data window was reduced to less than one cycle to ensure that the correct offset is rapidly computed. The effects of different numbers of the data samples per cycle are discussed. The simulations revealed that the DNN autoencoder stack reduced the size of the data window to approximately 90% of a cycle waveform, and that DNN performance accuracy depended on the number of samples per cycle (32, 64, or 128) and the training dataset used. The fewer the samples per cycle of the training dataset, the more training was required. After training using an adequate dataset, the delay in the correct magnitude prediction was better than that of the partial sums (PSs) method without an additional filter. Similarly, the proposed DNN outperformed the DNN-based full decay cycle dc offset in the case of converging time. Taking advantage of the smaller DNN size and rapid converging time, the proposed DNN could be launched for real-time relay protection and centralized backup protection.

Bowland Shale well placement strategy – Part 2: Fracture simulations using a 3D geomechanical model and implications for stratigraphic and spatial horizontal well locations

Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress environment in which these are propagating. However, spatial and stratigraphic variations in the stress and geomechanical properties of shales make accurate modelling a challenging task. For the UK Bowland Shale, stacked horizontal wells targeting multiple stratigraphic intervals could be used to avoid large offset faults in a geologically complex area. However, it is not known how these intervals may respond to hydraulic fracturing and predicting the height and length of hydraulic fractures is necessary in order to assess the likelihood of vertical fracture interference across landing zones or propagation towards major faults. In the case of the former, intervals of high effective stress may be key to containing fractures within their desired target. Using a planar hydraulic fracture simulator, and a 3D geomechanical model incorporating dipping stratigraphy, the issue of predicting hydraulic fracture geometry in the Bowland Shale was assessed through a series of modelling exercises using well Preese Hall-1 and horizontal pseudo-wells. When pre-defined landing zones were targeted, narrow and long transverse fractures around 1 km from the well were simulated. When the simulation design mimicked perforation clusters placed at 12 m intervals along horizontal pseudo-wells, the effects of stress shadowing were acute and resulted in irregular fracture geometries. Furthermore, high effective stress intervals performed efficiently as barriers to vertical hydraulic fracture propagation, reinforcing the feasibility of using stacked production for the Bowland Shale. The modelling results were then used to discuss the possible placement of horizontal wells in a mapped, 100 km2 region around well Preese Hall-1, where up to 13 sites could be positioned, with a horizontal well length of around 1.5 km. Finally, by drawing on a well-established analogue for the Bowland Shale, it was estimated that up to 195 Bcf of gas could be produced from the 13 locations in the area if three stratigraphic intervals are produced from one location.

Experimental study on gasketed bell-and-spigot joint behaviour of lined-corrugated HDPE pipe subjected to normal fault

Although the structural response of pipelines has been studied in relation to different geohazards, few studies have focused on the behaviour of flexible pipeline joints. In this paper, the response of a bell-and-spigot joint in a 600 mm dia. lined-corrugated high-density polyethylene (HDPE) pipe was investigated under differential ground movements imposed using a facility that simulates a normal fault. Two experiments were undertaken in this facility. In the first experiment, the kinematic responses of the pipe joint (i.e. axial, shear displacements and rotational angles) were measured using particle image velocimetry and string potentiometers. Strains were also monitored using optical fibres. In the second experiment, the pipe was sealed and leakage of the joint was captured through monitoring the internal vacuum pressure of the pipe. The results show that axial shortening, rotational angle and shear displacement of the pipe joint increased with increasing fault offsets. The joint began to leak when axial shortening, rotational angle and shear displacement of the pipe joint were 0·65 mm, 0·44° and 3·40 mm, respectively, and the joint clearly lost its functionality when those values reached 0·85 mm, 0·58° and 4·32 mm.

Investigating thermostat sensor offset impacts on operating performance and thermal comfort of three different HVAC systems in Wuhan, China

For heating, ventilation and air-conditioning systems (HVACs), their operating performance depends largely on sensors and their accurate measurements. Various types of faults are inevitable to sensors amounted in HVACs during the system lifespan, which eventually makes system deviated from the normal operation. To explore sensor fault impacts on different HVACs, the thermostat offset fault was taken as an example. For the same office building in Wuhan, this study compared its influences on operational performance of three HVACs including the ground source heat pump (GSHP) system, the variable refrigerant flow (VRF) system and the chiller + boiler (CB) system. The three HVACs were simulated simultaneously by EnergyPlus for the same target building with same outdoor meteorological environment to make a relatively fair comparison. The thermostat offset fault was introduced into the three HVACs with bias amplitudes ranging from −5–5 °C at the interval of 1 °C. Further, the fault impacts were quantitatively analyzed from three aspects in terms of system energy consumption, operating performance and indoor thermal comfort. Results indicated that the thermostat offset fault with different bias amplitudes and offset directions have different impacts on the three systems. Compared with the other two systems, GSHP is less affected by the introduced thermostat offset fault.

Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México

AbstractFaults on microcontinents record the dynamic evolution of plate boundaries. However, most microcontinents are submarine and difficult to study. Here, we show that the southern part of the Isla Ángel de la Guarda (IAG) microcontinent, in the northern Gulf of California rift, is densely faulted by a late Quaternary‐active normal fault zone. To characterize the onshore kinematics of this Almeja fault zone, we integrated remote fault mapping using high‐resolution satellite‐ and drone‐based topography with neotectonic field‐mapping. We produced 13 luminescence ages from sediment deposits offset or impounded by faults to constrain the timing of fault offsets. We found that north‐striking normal faults in the Almeja fault zone continue offshore to the south and likely into the nascent North Salsipuedes basin southwest of IAG. Late Pleistocene and Holocene luminescence ages indicate that the most recent onshore fault activity occurred in the last ∼50 kyr. These observations suggest that the North Salsipuedes basin is kinematically linked with and continues onshore as the active Almeja fault zone. We suggest that fragmentation of the evolving IAG microcontinent may not yet be complete and that the Pacific‐North America plate boundary is either not fully localized onto the Ballenas transform fault and Lower Delfin pull‐apart basin or is in the initial stage of a plate boundary reorganization.

Flexural strike-slip basins

AbstractStrike-slip faults are classically associated with pull-apart basins where continental crust is thinned between two laterally offset fault segments. We propose a subsidence mechanism to explain the formation of a new type of basin where no substantial segment offset or syn-strike-slip thinning is observed. Such “flexural strike-slip basins” form due to a sediment load creating accommodation space by bending the lithosphere. We use a two-way coupling between the geodynamic code ASPECT and surface-processes code FastScape to show that flexural strike-slip basins emerge if sediment is deposited on thin lithosphere close to a strike-slip fault. These conditions were met at the Andaman Basin Central fault (Andaman Sea, Indian Ocean), where seismic reflection data provide evidence of a laterally extensive flexural basin with a depocenter located parallel to the strike-slip fault trace.

Seismic stratigraphy, sedimentary facies analysis and reservoir characteristics of the Middle Jurassic syn-rift sediments in Salam Oil Field, north Western Desert, Egypt

The Middle Jurassic syn-rift sediments (Khatatba Formation) of the Western Desert, Egypt hosting potential reservoir intervals are prospective targets for hydrocarbon exploration and development campaigns. However, their depositional evolution and factors controlling distribution of the best reservoir faces are not very well-constrained. This work integrates seismic, well logs and conventional core dataset in order to define the syn-rift sedimentary patterns and their impact on distribution and quality of the reservoir facies. Khatatba Formation comprises two discrete units; the lower unit constitutes lower progradational and upper retrogradational sedimentary packages that are interpreted in terms of discrete rift phases. Nine sedimentary facies associations (FA) were recognized and their stacking patterns are governed by the rift evolution and the interplay between variation in fault offsets and sediment supply. Distal sand bar sandstones, marine shales and organic-rich shales were accumulated during periods of high subsidence. Successive alternation between shallow and deep facies at the base of the lower unit reveals repeated short periods of progradation and retrogradation with an overall progradational trend reflecting an elevated rate of sediment supply.Episodic fault-controlled retrogradation and progradation continued during the deposition of the Khatatba upper unit where the progradational deltaic facies changes upward into retrogradational marine sediments and aggradational-progradational aeolian and shoreface sandstones. Five hydraulic flow units (HFUs) were identified and their distribution is mostly controlled by the rift evolution. The lowest reservoir quality HFU4 and HFU5 are often associated with the retrograding distal facies accumulated during highest rates of subsidence. These zones do not contribute to more than 10% of the reservoir flow capacity. On the other hand, the progradational deltaic facies accounts for approximately 85% of the reservoir flow capacity in both lower and upper Khatatba units.

Geophysical characterization of volcanic layering

Seismic methods, electrical resistivity, and outcrop observations provide an integrated subsurface view of young basaltic lavas and their overlying weathered products. The study site is a sea cliff in the Kohala province in the northwestern part of the Big Island of Hawai'i, which provides an ideal laboratory for combined seismic reflectivity, shear-wave velocity, electrical resistivity, and outcrop observations. Our primary observation is the division of the shallow subsurface into weathered (saprolite) and underlying unweathered (hard basalt) zones. Significant heterogeneity is evinced by strong reflectivity changes within and between the two zones and the structural variability of the basal surface separating the weathered zone from the unweathered zone (reflector undulations, fault offsets, and prominent diffractions). Seismic reflectivity contrasts arise from variations in rigidity and porosity (density) corresponding to seaward-dipping lava flow units. The degree of clay alteration is interpreted to govern subsurface resistivity variations along with the influence of fresh groundwater and the incursion of seawater saturating the porosity. Our study provides a generalized model for visualizing weathered versus unweathered basaltic lavas in the shallow subsurface.

Stream channel offsets along strike-slip faults: Interaction between fault slip and surface processes

Stream-channel offsets are widely used for identifying strike-slip faults and estimating fault slip rates, assuming offsets result from fault slip. However, surface processes can modify and change stream channels. Here, we used a simple numerical model to investigate morphological evolution of stream channels due to both strike-slip fault slip and surface processes. Our results show competing effects: whereas fault slip offset stream channels, surface processes tend to modify fault offsets. Small fault offsets (a few meters) could be reconnected and straightened by new stream channels in a few hundred years or less. Over longer time, the cumulative effects of repeated fault slip and surface processes could lead to channels that are obliquely curved across the fault trace and differ from sharp and clear fault-offset stream channels. The morphological evidence of fault-offsets would be better preserved when the recurrence intervals of fault slip is shorter, and the fault zone is weaker. On the other hand, long recurrence intervals of slip events, irregular initial landforms, and complications of stream channel development such as stream capture, enhance the modification of fault-offsets of stream channels. We systematically examined the effects of major factors, including recurrence intervals of fault slip, diffusion and incision coefficients, and time-dependent variations of incision. Our results call for careful studies of surface processes when using stream-channel offsets to infer fault slip and estimate slip rates.

Latest Pleistocene–Holocene Incremental Slip Rates of the Wairau Fault: Implications for Long‐Distance and Long‐Term Coordination of Faulting Between North and South Island, New Zealand

AbstractWe use high‐resolution lidar microtopographic data and luminescence dating to constrain incremental Holocene–latest Pleistocene slip rates for the Wairau fault, a major dextral strike‐slip fault in the Marlborough Fault System, South Island, New Zealand. Our data come from two closely spaced study areas along the structurally simple, central portion of the fault: The well‐known Branch River terrace flight, and a previously undated series of offset risers and channel features several km to the east that we refer to as the Dunbeath site. Field work and mapping using lidar‐derived topography yields revised or novel measurements of nine fault offsets. We date those features using a post‐IR50‐IRSL225 infrared stimulated luminescence dating method, and a stratigraphically informed Bayesian age model. The dated slip history of the Wairau fault is further constrained using newly cataloged offset measurements collected along a ∼35 km stretch of the fault, and available paleoseismic data. Incremental slip rates are precisely computed using a Monte Carlo resampling scheme. Our results provide a nearly earthquake‐by‐earthquake record of incremental slip, with pronounced variations in incremental slip rate spanning multiple millennia and tens of m of slip. These extreme, multi‐millennial variations in fault slip rate have basic implications for earthquake occurrence, plate boundary lithosphere behavior, and probabilistic seismic hazard assessment.