Recent Fault Research Articles

Constraining timing of Proterozoic fault movement in the Capricorn Orogen, Western Australia

Ancient faults dissect low-grade Mesoproterozoic sedimentary rocks of the 1673–1455 Ma Edmund Basin and the 1455–1075 Ma Collier Basin in the Capricorn Orogen, Western Australia, and reveal a protracted history of basin formation and subsequent deformation. K–Ar dating of illite from fine-grained fault gouge separates (ideally <0.1 µm) provide robust dates of the most recent fault movement. From the Godfrey–Mount Vernon Fault, a sample of siltstone from the Kiangi Creek Formation (1590–1514 Ma) in the Edmund Basin, which was collected adjacent to faulting, provided a whole-rock date of 1506 ± 30.2 Ma. This is interpreted as a mixed age, encompassing modification of the depositional age by subsequent faulting during the extensional opening of the Edmund Basin. A fault gouge sample dated at 1141.4 ± 58.6 Ma, also from the Godfrey–Mount Vernon Fault, is consistent with the tectono-thermal 1321–1171 Ma Mutherbukin Tectonic Event identified in underlying high-grade Gascoyne Province basement rocks. Fault gouge sample dates of 885.5 ± 45.9 Ma from the Godfrey–Mount Vernon Fault and 782.2 ± 40.1 Ma from the Quartzite Well Fault define the younger newly identified crustal shortening during the Kuparr Tectonic Event. Concomitant tectonic activity in eastern Australia and South China has been considered as a possible precursor of the breakup of Rodina. In southern Africa, the Zambezi Supracrustal Sequence has been dated at 880–820 Ma and the Munali Intrusive Complex at 862–857 Ma also identified as rift-related.

Crustal Structure of Southern California from Velocity and Attenuation Tomography

Recent studies of Southern California have employed velocity and attenuation tomography to elucidate two aspects of crustal structure. Low-frequency velocity tomography reveals large-scale heterogeneity that can be approximated by a discrete set (𝐾 ≤ 10) of tectonic regions, each characterized by an isostatically balanced lithospheric column reflecting the composition and tectonic history of the region. The boundaries between tectonic regions are typically localized structures expressed at the surface by major faults, topographic fronts, and geochemical transitions. The efficacy with which tomographic regionalization (TR) represents the subsurface geography of major tectonic units in Southern California indicates that the TR idealization works surprisingly well in this part of the Pacific‐North America plate boundary. High‐frequency attenuation tomography in Southern California supports the hypothesis that the decay of P and S waves propagating through the upper and middle crust is dominated by elastic scattering from small-scale heterogeneities of high fractal dimension, rather than by anelastic dissipation. The amplitude of the scattering varies systematically among the tectonic regions and correlates with the degree of recent faulting and deformation within a region. These results motivate speculation that small-scale crustal heterogeneities responsible for high-frequency attenuation are generated within the seismogenic zone through a dynamic interplay between distributed deformation and localized fracturing.

Imaging and modelling the subsurface structure of the Rungwe Volcanic Province in SW Tanzania with aeromagnetic data: An improved structural map to support geothermal exploration

The Rungwe Volcanic Province (RVP) in the East African Rift System, SW Tanzania, provides a unique opportunity to investigate geothermal resources in the context of particularly complex continental rifting processes. To support geothermal resource targeting in the RVP, we present a revised neotectonic structural map based on an interpretation of aeromagnetic data constrained by 2D-forward modelling of magnetic anomalies integrated with the distribution of previously reported faults, seismic epicentre locations, 3D magnetotelluric resistivity models and surface geothermal manifestations. Magnetic anomalies in the RVP, including the nationally prominent Mbeya anomaly, are related to the high magnetic susceptibility or remanent magnetism of Precambrian rocks and Cretaceous carbonatite intrusions buried in the rift under a varying thickness of non-magnetic sediments and volcanic rocks. Magnetic lineaments are related to structures controlling the geometry of the Precambrian rocks and concealed dikes and the thickness of the sediments and volcanics. The recent Ngozi and Rungwe trachyte volcanics have relatively low magnetic susceptibility comparable to the low susceptibility of the sediments in the rift basins. The revised neotectonic structural map shows prominent NW, NE and NS-trending magnetic lineaments that correlate with previously reported faults and alignments of seismic epicentres in the study area and with the regional trend of the rift segments. The NE-trending magnetic lineaments are consistent with interpretations of the current stress field in the RVP. The main volcanoes in the RVP, Ngozi, Rungwe and Kiejo (also known as Kyejo and Kieyo), are aligned with the NW-trending linear magnetic feature joining the Lupa and Livingstone rift border faults. This lineament is intersected and frequently displaced by the NE and NS-trending lineaments, suggesting that the NE to NS-striking structures are younger. The Rungwe and Ngozi volcanoes as well as numerous ‘’monogenetic’’ eruption centres and the Mwakaleli caldera, which originated ca. 2 Ma ago (Ebinger et al., 1989) following a large explosive eruption emplacing widespread ignimbrite deposits, are located within a zone of low-intermediate magnitude magnetic features forming a basin-like structure surrounded by magnetic high anomalies of the Precambrian basement structures. We interpret the intersections between the NW-trending intra-rift faults and the NS and NE-trending faults as favourable locations for wells to target high permeability within the geothermal resource conceptual models previously constructed using 3D MT resistivity imaging integrated with supporting geoscientific data. The intersections provide a focus area for follow-up ground mapping of subtle features that may be associated with very recent fault movement.

Forearc crustal faults as tsunami sources in the upper plate of the Lesser Antilles subduction zone: the case study of the Morne Piton fault system

Abstract. In this study, alternatively to the megathrust, we identify upper-plate normal faults orthogonal to the trench as a possible tsunami source along the Lesser Antilles subduction zone. The Morne Piton fault system is such a trench-perpendicular upper crustal fault at the latitude of Guadeloupe. By means of seismic reflection, high-resolution bathymetry, remotely operated vehicle (ROV) imaging and dating, we reassess the slip rate of the Morne Piton fault since 7 Ma, i.e., its inception, and quantify an average rate of 0.25 mm yr−1 since ca. 1.2 Ma. This result divides by two previous estimations, increases the earthquake time recurrence and lowers the associated hazard. The ROV dive revealed a metric scarp with striae at the toe of the Morne Piton fault system, suggesting a recent fault rupture. We estimate a fault rupture area of ∼ 450–675 km2 and then a magnitude range for a maximum seismic event around Mw 6.5 ± 0.5, making this fault potentially tsunamigenic as the nearby Les Saintes fault responsible for a tsunami following the 2004 Mw 6.3 earthquake. Consequently, we simulate a multi-segment tsunami model representative of a worst-case scenario if all the identified Morne Piton fault segments ruptured together. Our model provides clues for the potential impact of local tsunamis on the surrounding coastal area as well as for local bathymetric controls on tsunami propagation. We illustrate that (i) shallow-water plateaus act as secondary sources and are responsible for a wrapping of the tsunami waves around the island of Marie-Galante; (ii) canyons indenting the shallow-water plateau slope break focus and enhance the wave height in front of the most touristic and populated town of the island; and (iii) the resonance phenomenon is observed within the Les Saintes archipelago, showing that the waves' frequency content is able to perturb the sea level for many hours after the seismic rupture.

Investigation of suspected Holocene fault scarp near Montréal, Québec: The first paleoseismic trench in eastern Canada

Investigation of suspected Holocene fault scarp near Montréal, Québec: The first paleoseismic trench in eastern Canada

Recent Holocene activity and regional tectonic significance of the northern segment of the red river fault zone

The Red River Fault Zone is a large-scale right-lateral strike-slip fault zone with relatively strong activity during the Quaternary Period. This fault, located on the southeastern margin of the Qinghai‒Tibetan Plateau, plays a key role in the extrusion, rotation and escape of the continental blocks constituting the Qinghai‒Tibetan Plateau. Furthermore, this fault represents the southwestern boundary of the Sichuan–Yunnan Block, which has experienced strong deformation and frequent seismic activity. The northern segment of the Red River Fault Zone is the most active part of the whole fault. However, surface erosion and vegetation coverage have obscured the activity of the northern segment; therefore, the study of its activity has obviously been insufficient. There is still controversy over whether all the secondary faults on the northern segment are active Holocene faults. Studying the activity characteristics of the northern segment, which is densely populated, is particularly important for seismic risk prevention in this area. Based on remote sensing interpretations and field geological surveys, this paper describes the latest activity characteristics of the Cangshan Piedmont Fault, Fengyi–Dingxiling Fault and Midu Basin Margin Fault, including their spatial distributions and kinematic characteristics. According to the ages of the offset strata in profiles, the above three secondary faults were all active in the late Holocene. The latest active age of the Cangshan Piedmont Fault was later than 543-494 cal BP, and two palaeoseismic events that occurred in this section during the Holocene occurred at 2700 and 473 cal BP. The latest active age of the Fengyi–Dingxiling Fault was later than 2760–2700 cal BP; in this section, one Holocene palaeoseismic event occurred between 1777 cal BP and 2730 cal BP, another occurred between 2730 cal BP and 5664 cal BP, and the third occurred between 6449 cal BP and 8360 cal BP. The latest active age of the Midu Basin Margin Fault was later than 558-510 cal BP, and two Holocene palaeoseismic events occurred later than 2318-2114 cal BP and 558-510 cal BP. Based on the results of this paper and previous studies, we believe that the Fengyi–Dingxiling Fault on the northern segment of the Red River Fault Zone is at risk for future strong earthquakes. Additionally, abundant geological and geomorphologic evidence suggests that the northern segment is dominated by normal faults, reflecting the local strain response to secondary clockwise rotation of the Sichuan–Yunnan Block along the boundary fault. This finding is in line with the eastwards extrusion and escape of materials on the Qinghai‒Tibetan Plateau caused by the northwards and northeastwards pushing of the Indian Plate. To a certain extent, these observations reflect the tectonic deformation coordination between block rotation and boundary fault slip in the Sichuan–Yunnan Block in the context of continental block extrusion on the Qinghai–Tibetan Plateau.

Structural Uncertainty Due to Fault Timing: A Multimodel Case Study from the Perth Basin.

Faults can fundamentally change a groundwater flow regime and represent a major source of uncertainty in groundwater studies. Much research has been devoted to uncertainty around their location and their barrier-conduit behavior. However, fault timing is one aspect of fault uncertainty that appears to be somewhat overlooked. Many faulted models feature consistent layer offsets, thereby presuming that block faulting has occurred recently and almost instantaneously. Additionally, barrier and/or conduit behavior is often shown to extend vertically through all layers when a fault may in fact terminate well below-ground surface. In this study, we create three plausible geological interpretations for a transect in the Perth Basin. Adjacent boreholes show stratigraphic offsets and thickening which indicate faulting; however, fault timing is unknown. Flow modeling demonstrates that the model with the most recent faulting shows profoundly different flow patterns due to aquifer juxtaposition. Additionally, multiple realizations with stochastically generated parameter sets for layer, fault core, and fault damage zone conductivity show that fault timing influences flow more than layer or fault zone conductivity. Finally, fault conduit behavior that penetrates aquitards has significant implications for transport, while fault barrier behavior has surprisingly little. This research advocates for adequate data collection where faults may cause breaches in aquitards due to layer offsets or conduit behavior in the damage zone. It also promotes the use of multiple geological models to address structural uncertainty, and highlights some of the hurdles in doing so such as computational expense and the availability of seamless geological-flow modeling workflows.

The Intraplate Stress Field of West Africa

AbstractWest Africa continues to host a growing number of low and intermediate‐magnitude earthquakes (M2‐5) along its passive margins, and its continental interior. Earthquake activity in these regions raises the need to comprehend the causes and the tectonic controls of the seismicity. Unfortunately, such studies are rare. Here, we apply single‐station inversion techniques to constrain fourteen focal mechanisms, computed after compiling a set of high‐quality waveforms. We describe the connection between seismicity, the contemporary stress field, anthropogenic activity and Holocene fault scarps in the region. Our results indicate transpressive stresses acting on the inherited brittle structures in the passive margins. We also observe a compressive regime in the intracontinental failed rifts. We attribute the seismicity to the reactivation of “weak” faults in the Neoproterozoic and Mesozoic failed rifts, the passive transform structures, and the intracratonic Precambrian brittle shear zones.

PCDC: Prototype-assisted dual-contrastive learning with depthwise separable convolutional neural network for few-shot fault diagnosis of permanent magnet synchronous motors under new operating conditions

Abstract The fault diagnosis of permanent magnet synchronous motor is of vital importance in industrial fields to ensure user safety and minimize economic losses from accidents. However, recent fault diagnosis methods, particularly the methods using deep learning, require a massive amount of labeled data, which may not be available in industrial fields. Few-shot learning has been recently applied in fault diagnosis for rotary machineries, to alleviate the data deficiency and/or to enable unseen fault diagnosis. However, two major obstacles still remain, specifically: a) the limited ability of the models to be generalized for use under new operating conditions and b) insufficient discriminative features to precisely diagnose fault types. To address these limitations, this study proposes a Prototype-assisted dual-Contrastive learning with Depthwise separable Convolutional neural network (PCDC) for few-shot fault diagnosis for permanent magnet synchronous motors under new working conditions. Operation-robust fault features are extracted to reinforce generalization of PCDC under new operating conditions by extracting fault-induced amplitude and frequency modulation features and by eliminating the influence of operating conditions from the motor stator current signals. Prototype-assisted dual-contrastive learning is proposed to clearly distinguish the fault categories even when the fault features are similar to each other by learning both local- and global-similarity features, which increases the instance-discrimination ability while alleviating an overfitting issue. Experimental results show that the proposed PCDC outperforms the comparison models in few-shot fault diagnosis tasks under new operating conditions.

Large paleoearthquakes and Holocene faulting in the Southeastern Gorny Altai: implications for ongoing crustal shortening in Central Asia

ABSTRACT Shrinking of intermontane basins and expansion of their flanking ranges by reverse faulting and backthrusting in two counter-dipping systems is a typical mechanism of crustal shortening and mountain building in Central Asia. This mechanism is realized along the Kurai Fault Zone (southeastern Gorny Altai). Motions on two reverse fault systems maintained thrusting of the Kurai Range and the Kubadru Uplift on the Kurai Basin sediments and caused the growth of a foreberg before the mountain front. Forberg separates narrow Aktash Basin from the Kurai Basin. The paleoearthquakes were generated by reverse faults that delineate the foreberg. Analysis of the QuickBird satellite images, drone imagery, trenching, archaeoseismological research, radiocarbon dating, dendrochronology, and previous results show that eleven large (М W = 6.5–7.6) paleoearthquakes left traces as surface ruptures along the Kurai Fault Zone: twice before 7.5 ka BP, three events between 7.5 and 5.9 ka BP (7.0, 6.3, and 5.9–5.8 ka BP), one from 5.8 to 4.6 ka BP, four more at 4.6, 3.2, 1.5, and 1.3–1.2 ka BP, and the ultimate earthquake no older than 1450–1650 AD. The time difference between large earthquakes was from 200 to 1700 years. Surface faulting occurred mainly along the northern border of the foreberg where fault scarps are progressively younger northward and the Cenozoic sediments of the Aktash Basin thus become involved into uplift. GPR data to a depth of 12 m confirm the complex structure and slip geometry of the observed surface ruptures. The fault scarps are located < 1 km from the planned route of the gas pipeline from Russia to China, and the potential seismic hazard has to be taken into account in its design and construction.

Messinian canyons morphology of the Rhône and Ardèche rivers (south-east France): new insights from seismic profiles

Twelve available two-way time high-resolution seismic reflection profiles located in the central part of the middle Rhône valley are interpreted. In addition, one of the profiles was reprocessed to determine the P-wave velocities of the main geological units and to convert this profile into a depth cross section. The Lower and Upper Cretaceous units are clearly identifiable on all the profiles, along with the Messinian Erosion Surface (MES) carved out during the Messinian Salinity Crisis (MSC) by the paleo-Rhône and its western tributaries, the Ardèche and Cèze paleo-canyons. The Plio-Quaternary fill of these paleo-canyons shows at least 4 main units with an overall transgression. The combination of geological data from geological maps, geological field surveys and borehole data made it possible to model the MES in 3D at the scale of the region, and to produce depth/elevation model. From a geological point of view, the interpretation of the seismic profiles enabled us to reconstruct the stages in the sub-aquatic filling of the Messinian-Pliocene aggradation of the paleo-river. Several Mass Transport Deposits (MTDs) were identified both during the drop and during the rise in the Mediterranean Sea level. From a geomorphological point of view, this study provides new insights in the route and longitudinal profile of paleo-rivers and, in particular, it deepens the profile of the Paleo-Rhône at the latitude of the Tricastin region (up to −700 m b.s.l.) and significantly modifies the course and depth of the Ardèche proposed in previous studies. The N-Ardèche river, known to develop a karstic system during the MSC, is connected to a deep canyon, most likely through a karstic pocket valley, as suggested by the very steep longitudinal profile of the MES. Finally, from a structural point of view, our interpretation of the seismic profiles shows a broad ENE-trending anticline structure associated with a normal fault which apparently did not affect the Mio-Pliocene fill. In the southern part of the area, near the Uchaux anticline, the imaged structures suggest the presence of a recent (syn- to post-Pliocene) fault propagation fold. In addition to all the new information on the geology, morphology and methods of excavation and filling of the Messinian paleo-canyon, the proposed topographic model of the paleo-canyon is crucial for modelling seismic movement in the context of a basin with a complex geometry and, in particular, for the numerical assessment of site effects in a context of low seismicity.

Late Quaternary deformation, strain partitioning, and fold-thrust belt widening in the Eastern Himalayan Syntaxis, India

The easternmost Himalaya near the 96°E longitude shows a sharp ~90° orogenic bend known as the Eastern Himalayan Syntaxis. A complicated configuration of the region and related space problems, combined with extreme vigorous erosion and surface processes makes it difficult to understand the strain release pattern, slip rate on the participating thrust/s, and the seismic potential of the geological structures. To understand the deformation pattern in the region, luminescence and radiocarbon dating methods were used on deformed landforms in the frontal Siang and Mishmi ranges of the Eastern Himalayan Syntaxis. We obtained fault slip rates of Late Quaternary period. The Holocene rates range over 7.5 ± 0.2 mm/yr in the northern segment, 1 ± 0.1 to 10.1 ± 1.5 mm/yr in the central segment, and 8 ± 0.5 mm/yr in the southern segment of the Mishmi Thrust, whereas the Late Pleistocene rates are of the order of 1 ± 0.1 mm/yr in the central segment and 0.9 ± 0.1 mm/yr in the southern segment of the Mishmi range. The obtained Late Pleistocene rates are lesser than the Holocene rates, but consistent with exhumation rates reported earlier from the northern segment. Holocene fault slip rates of the range 2–9.1 mm/yr across the Manabhum Anticline suggest foreland strain partitioning due to widening of the fold-thrust belt and the locked zone. A widening of the locking width implies an increase in the seismic potential of the region. We suggest that the Manabhum Thrust is possibly a proto-thrust or else a footwall imbrication of the Mishmi Thrust. Contrastingly, a lesser Holocene fault slip rate of 2.3 ± 0.3 mm/yr obtained from the eastern Siang range along the Main Boundary Thrust indicates considerable strain partitioning in the hinterland. Results demonstrate that in tectonically active regions, representative rates of rock uplift inferred from incised bedrock should be integrated over at least one complete seismic and inter-seismic cycle.

Seismic potential on the northwestern Main Recent Fault (Iran) revealed by InSAR

The Main Recent Fault (MRF) is an important boundary fault that accommodates the oblique convergence motion between the Arabian and Eurasian plates. Several large earthquakes including the 1909 Mb 7.4, 1958-1963 three events with magnitude larger than Mw 6.0, and the 2006 Mw 6.1 earthquake had partly ruptured the central and southeast segments of MRF. However, there is no large earthquake occurred in the northwest segment in the past hundred years. In this study, the interseismic surface deformation was firstly mapped from the Synthetic Aperture Radar (SAR) images observed by the Sentinel-1 satellite. Then, the ununiformed fault slip rate, coupling ratio and locking depth are estimated based on the measured interseismic surface deformation. The results show that the interseismic fault slip rate slightly varies from ~3.7 mm/yr to ~6.1 mm/yr along the MRF. Furthermore, it is also found a gradual increasing extensional component with magnitude of 2-7 mm/yr from Morvarid to Sahneh segments of MRF. In addition, total 9 sub-segments could be divided based on the fault coupling distribution and historical earthquakes in the interest zone. A seismogenic zone is identified from the historical earthquakes, which has a good space consistency with the transition between the significant shallow locking and deep free slip zones. According to the potential seismic magnitude and estimated recurrence interval, it is found that several segments are approaching the end of their interseismic recurrence interval. Meanwhile, one segment (SF-8) may be in the early stage of a new recurrence period due to the recent several large earthquakes and a long recurrence interval.

Method of co-seismic fault displacement estimate based on peak ground acceleration

Based on the results of the seismic hazard survey in Yunnan Province, four exceedance probabilities of peak ground acceleration were converted into earthquake magnitudes using the empirical relationship between epicentral intensity and magnitude. By using logistic regression, earthquake magnitude, source depth, cover layer thickness, and fault type were used as independent variables to calculate the probability of co-seismic displacement for different earthquake magnitudes. Using the magnitude-displacement empirical model in the southwestern region of China, horizontal and vertical displacements were obtained with a 95 % confidence level. The results show that all Holocene faults have the ability to produce surface displacement, but from the perspective of probabilistic hazard, the probability of surface rupture in the short term is low, while the probability of surface rupture for each fault significantly increases over a long time scale. Buildings with different service lives should adopt different avoidance strategies, and buildings with shorter service lives (&lt;50a) can consider not avoiding active faults.

The Chaman and Paghman active faults, west of Kabul, Afghanistan: Active tectonics, geomorphology, and evidence for rupture in the destructive 1505 earthquake

The city of Kabul, Afghanistan, lies within the Kabul Block, which is bounded by the Sarobi, Gardez and Paghman fault, the northern extension of the Chaman fault, accommodating oblique convergence between the Indian and Eurasian plates. In this paper, we describe the geologic structure and tectonic geomorphology of the northeast-striking Paghman fault and a ∼10-km-long portion of the Chaman fault using a combination of field observations and remote sensing data, and assess evidence for rupturing in the 1505 historical earthquake. The Paghman fault is predominantly a left-lateral strike-slip fault with a minor dip-slip component along the eastern margin of the Paghman Mountains. The Chaman and Paghman faults displaces Paleogene to Quaternary units with clear displacement of recent deposits. Continuous left-lateral movement of the both faults have caused stream deflection, capturing, abandonment, and finally, incision of alluvial deposits inside the Kabul Basin. We identify several stages in the alluvial fan development and displacement that were once a continuous unit displaced left-laterally as a single fan but are now incised by beheaded and offset stream channels. An approximately 30-km-long active fault trace is identified with geomorphic evidence of recent faulting and vertical offset ∼0.5–3 m, which we interpret is related to the historical 1505 earthquake in the area along the Chaman and Paghman faults. Our observations indicate significant along-strike variations in faults trace geometry. The seismic event comprises several fault segments separated by discontinuities such as stepovers. The two faults have accumulated enough elastic strain to cause a larger earthquake since the 1505 quake.

The deep structure of the Zagros mountain system according to Taylor approximation seismic tomography data

The seismic tomographic model obtained by the Taylor approximation method provides new constraints on the Earth’s crust and mantle structure beneath the Zagros mountain system at depths of 50—850 km. Based on structural geology and seismic tomography data, we divide the Zagros into Northwestern (Kirkuk, Lurestan, and Dezful regions) and Central (Kazerun and Fars regions) parts. The Central Zagros was formed due to subduction-collision tectonics, and the Northwestern Zagros was formed due to a collision-shear (transpression) tectonic process. Based on the 3D P-velocity model of the Zagros and its surrounding mantle, a high-velocity distal southeastern part of the Arabian Plate was established, subducting under the Central Zagros and the Iranian Plate, following the subduction of the Neotethys. This slab covers an area of 23—32°NL — 49—58°EL, i.e., the Bay of Bengal, the Central Zagros, and the southern part of the Iranian Plate. The maximum horizontal extent of the submerging part of the Arabian slab is 800—1100 km, and the maximum submersion depth is 450—500 km. A number of projections on the horizontal plane of the lines of intersection of the surface of the subducting Arabian Plate with horizontal sections of 50, 100, 200, 300, and 400 km were constructed. We obtained the direction of plate plunging, which in different areas varies from northern to northeastern 30—45°. In the Northwestern Zagros, according to the model, traces of subduction do not appear; however, right-lateral strike-slip deformations along the Main Recent Fault are visible and continue now in the crust. The difference in the types of deformation of the Northwestern and Central Zagros is most likely due to the features of the outlines of the eastern edge of the Arabian Plate and the complex nature of its movements. Analysis of earthquake mechanisms in 1977—2001 shows that the movement of the Arabian Plate could have occurred with frequent alternation in the S-N and N-E directions due to the alternation of spreading processes in the Gulf of Aden and the southeastern part of the Red Sea.

Rift Basins and Intraplate Earthquakes: New High‐Resolution Aeromagnetic Data Provide Insights Into Buried Structures of the Charleston, South Carolina Seismic Zone

AbstractThe delineation of faults that pose seismic risk in intraplate seismic zones and the mapping of features associated with failed rift basins can help our understanding of links between the two. We use new high‐resolution aeromagnetic data, previous borehole sample information, and reprocessed seismic reflection profiles to image subsurface structures and evaluate recent fault activity within the Charleston seismic zone, the associated Mesozoic South Georgia rift basin, and surrounds. The new aeromagnetic data provide an unprecedented view of buried basement structures. NE‐ and NW‐trending lineaments of various lengths throughout the survey area are interpreted as Paleozoic orogenic structures and Mesozoic dikes, respectively. Within the rift basin, 15‐ to 20‐km long ESE‐trending lineaments are associated with faults in pre‐Cretaceous strata of the reflection data and are interpreted as Mesozoic rift structures. Various intersections and terminations of interpreted faults suggest rift‐related reactivation of Paleozoic faults and corresponding inheritance for Mesozoic structures. The reflection data show that several Paleozoic and Mesozoic faults are associated with deformation in Cretaceous and younger sediments, suggesting reactivation in the more recent passive margin setting. Two of these faults, one NE‐striking and one ESE‐striking, are coincident with surficial landforms, suggesting Quaternary slip; the ESE‐striking fault is also well‐aligned with a plan‐view offset in modern seismicity. A favorable orientation for reverse motion on ESE‐striking Mesozoic faults, a possible sub‐basin, and potentially weakened lithosphere are failed rift basin features that may influence intraplate seismicity within the Charleston seismic zone.

The geological situation in Abu-Jir Faults Zone, western Iraq: evidence from the radioactivity in Hit–Haditha area

Total radioactivity measurements (cps) in 59 sites were achieved in the Hit–Kubaiysa–Haditha area. Geological samples (soil and rock) from those sites were analyzed for Ra-226, U-238, Th-232, and K-40 using Gamma spectroscopy system based on high pure germanium. The study aims to assess the radioactivity in the study area and attempt to understand the relationship between radioactivity and the geological situation in the area. The results showed that many sites have relatively high total radioactivity exceeding the background radioactivity by many times. The radioactivity concentrated in areas around the springs spreading in the area caused by the high concentration of Ra-226 which being have disequilibrium with its parent U-238. Some areas also have a relatively high concentration of U-238 in depressions areas where the upper part of the Euphrates Formation is outcropped. Based on the pattern of the spread of total radioactivity in the study area, the extension of the Euphrates Fault Zone and the Abu Jir Fault Zone could be determined. These fault zones extend towards northwest–southeast, in addition to the delineation of some of the recent faults that intersect with these zones in an east–west direction, most of which follow the spreading pattern of the springs in the region.

Robust fault diagnosis of a high-voltage circuit breaker via an ensemble echo state network with evidence fusion

Reliable mechanical fault diagnosis of high-voltage circuit breakers is important to ensure the safety of electric power systems. Recent fault diagnosis approaches are mostly based on a single classifier whose performance relies heavily on expert prior knowledge. In this study, we propose an improved Dempster–Shafer evidence theory fused echo state neural network, an ensemble classifier for fault diagnosis. Evidence credibility is calculated through the evidence deviation matrix and the segmented circle function and employed as credibility weights to rectify the raw evidence. Then, an improved Dempster–Shafer evidence fusion algorithm is proposed to fuse evidence from different echo state network modules and sensors. Unlike conventional classifiers, the proposed methodology consists of multiple echo state neural network modules. It has better flexibility and stronger robustness, and its model performance is not sensitive to network parameters. Comparative analysis indicates that it can handle the paradox evidence fusion analysis and thus can achieve better diagnostic performance. The superiority of the reported fault diagnosis approaches is verified with the experimental data of a ZN12 high-voltage circuit breaker.

Possible Fault Communication between the Memphis Sand Aquifer and the Mississippi River

ABSTRACT The Eocene Memphis Sand aquifer is the major source of drinking water for municipalities in the upper Mississippi Embayment, with the city of Memphis, TN, being the largest consumer. Concerns about contamination of the Memphis aquifer from surface waters have primarily focused on local groundwater transmission through the Upper Claiborne aquitard and erosional windows through the aquitard. This study used recent fault mapping to show that faults extend upward from the Memphis aquifer to very near the surface in and adjacent to Memphis. The Meeman-Shelby and Cuba faults extend under the Mississippi River and upward to the base of the Mississippi River alluvium. Groundwater levels (potentiometric surface) in Memphis aquifer monitor wells H002 and LdF 004 and the Mississippi River water levels during the years of 2007 through 2011 show strong correlation (0.744829 and 0.779691, respectively). We believe this correlation may be due to direct connection through fault zones.