We quantified the systematic variations in global transform fault morphology,revealing a first-order dependence on the spreading rate.(1)The average age offset of both the full transform and transform sub-segments dec...We quantified the systematic variations in global transform fault morphology,revealing a first-order dependence on the spreading rate.(1)The average age offset of both the full transform and transform sub-segments decrease with increasing spreading rate.(2)The average depth of both the transform valley and adjacent ridges are smaller in the fast compared to the slow systems,reflecting possibly density anomalies associated with warmer mantle at the fast systems and rifting at the slow ridges.However,the average depth difference between the transform valley and adjacent ridges is relatively constant from the fast to slow systems.(3)The nodal basin at a ridge-transform intersection is deeper and dominant at the ultraslow and slow systems,possibly reflecting a lower magma supply and stronger viscous resistance to mantle upwelling near a colder transform wall.In contrast,the nodal high,is most prominent in the fast,intermediate,and hotspot-influenced systems,where robust axial volcanic ridges extend toward the ridge-transform intersection.(4)Statistically,the average transform valley is wider at a transform system of larger age offset,reflecting thicker deforming plates flanking the transform fault.(5)The maximum magnitude of the transform earthquakes increases with age offset owing to an increase in the seismogenic area.Individual transform faults also exhibit significant anomalies owing to the complex local tectonic and magmatic processes.展开更多
Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the ocean...Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the oceanic lithosphere remains poorly understood.The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an indepth view of the underlying detailed seismic structures,contributing to understanding geodynamic processes within the oceanic lithosphere.Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃isotherm.However,this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults.Several mechanisms have been proposed to explain these deep events,and we suggest that local geodynamic processes(e.g.,magma supply,mylonite shear zone,longlived faults,hydrothermal vents,etc.)likely play a more important role than previously thought.展开更多
Large strike-slip faults play a crucial role in regulating the geometry and kinematics of the solid Earth's outer lithospheric plates and the structural deformation of internal continents.They not only control the...Large strike-slip faults play a crucial role in regulating the geometry and kinematics of the solid Earth's outer lithospheric plates and the structural deformation of internal continents.They not only control the geometric structures,motion properties,and direction of the lithospheric plates,but also regulate the complex tectonic stress field and strain state caused by differential motion among multiple blocks within the continent,maintaining the relative stability of the overall stress state of the lithosphere on the Earth's surface.According to the nature and significance of geotectonic structures,strike-slip faults can be divided into interplate types and intraplate tectonic types.Interplate strike-slip faults are transform faults,including oceanic transform faults and continental transform faults.Intraplate strike-slip faults can be divided into continental transfer faults and intraplate transcurrent faults.During the lateral movement of lithospheric plates along the Earth's surface,transform faults adjust the differences in the nature,direction,and rate of movement between different plates.Meanwhile,continental transfer faults and intraplate transcurrent faults adjust the location,nature,style,and differential stress of intraplate tectonic deformation.Strike-slip faults of varying types and scales interact in different ways to maintain the dynamic balance of matter and energy within Earth's lithospheric plates.Based on the concepts,tectonic significance,and recent research advances of strike-slip faults and classical transform faults,this paper summarizes the latest classification of strike-slip faults and their corresponding tectonic implications.It also updates the definitions,geometric characteristics,and kinematic features of oceanic transform faults,continental transform faults,continental transfer faults,and intraplate transcurrent faults.Through typical global examples,this paper comprehensively analyzes the deep structure,structural geometry and kinematic characteristics,evolution process,geological significance,and seismic hazards of different types of strike-slip faults.Furthermore,the frontier science issue and research strategies for the study of oceanic transform faults,continental transfer faults,and intraplate transcurrent faults are summarized as well.展开更多
Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continent...Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continental transform faults based on the nature of their separated plates.Owing to significant differences in properties between continental and oceanic lithospheres,continental transform faults exhibit more complex structures than their oceanic counterparts.Continental transform faults are strike-slip boundaries where stress and strain are highly concentrated.They typically extend for hundreds to thousands of kilometers and have experienced tens to hundreds of kilometers of strike-slip displacement.These faults may appear as a single master fault or as complex fault systems with multiple branches.Their deep structures and deformation patterns at varying depths offer critical insights into the structure and rheological behavior of the continental lithosphere.Imaging fine-scale structures of continental transform faults via geophysical methods is crucial for understanding their nature and evolution.Seismic anisotropy results provide key constraints on their deep deformation characteristics.This paper reviews geophysical studies from typical continental transform fault regions and investigates their deep structure and deformation mechanisms by integrating geological and geodetic observations.Although these fault systems are structurally diverse,several common features emerge.(1)Nearly all continental transform faults cut through the entire crust and extend into the upper mantle,with significant seismic anisotropy observed within the fault zones.(2)Regardless of whether the fault is a single narrow structure or a branching system,uppercrustal segments typically form narrow zones of strain concentration where brittle friction accommodates slip and seismicity is concentrated.The shear zone broadens with depth,reaching tens of kilometers in width within the lithospheric mantle.(3)The width of a continental transform fault correlates with the nature of the lithosphere it cross-cuts.Narrow shear zones form in rigid and ancient lithosphere,otherwise,broader distributed deformation occurs.(4)Non-strike-slip components(compression or tension)significantly influence fault zone complexity.Recent ocean drilling programs have advanced understanding of oceanic transform faults,yet knowledge of continental transform fault structure and evolution remains limited.Advances in seismic imaging and observational techniques will enable higher-resolution characterization of these faults,providing new constraints on their seismic behavior and earthquake migration patterns.展开更多
Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes alon...Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.展开更多
The back propagation (BP)-based artificial neural nets (ANN) can identify complicated relationships among dissolved gas contents in transformer oil and corresponding fault types, using the highly nonlinear mapping nat...The back propagation (BP)-based artificial neural nets (ANN) can identify complicated relationships among dissolved gas contents in transformer oil and corresponding fault types, using the highly nonlinear mapping nature of the neural nets. An efficient BP-ALM (BP with Adaptive Learning Rate and Momentum coefficient) algorithm is proposed to reduce the training time and avoid being trapped into local minima, where the learning rate and the momentum coefficient are altered at iterations. We developed a system of transformer fault diagnosis based on Dissolved Gases Analysis (DGA) with a BP-ALM algorithm. Training patterns were selected from the results of a Refined Three-Ratio method (RTR). Test results show that the system has a better ability of quick learning and global convergence than other methods and a superior performance in fault diagnosis compared to convectional BP-based neural networks and RTR.展开更多
This paper presents an intelligent technique to fault diagnosis of power transformers dissolved and free gas analysis (DGA). Fuzzy Reasoning Spiking neural P systems (FRSN P systems) as a membrane computing with distr...This paper presents an intelligent technique to fault diagnosis of power transformers dissolved and free gas analysis (DGA). Fuzzy Reasoning Spiking neural P systems (FRSN P systems) as a membrane computing with distributed parallel computing model is powerful and suitable graphical approach model in fuzzy diagnosis knowledge. In a sense this feature is required for establishing the power transformers faults identifications and capturing knowledge implicitly during the learning stage, using linguistic variables, membership functions with “low”, “medium”, and “high” descriptions for each gas signature, and inference rule base. Membership functions are used to translate judgments into numerical expression by fuzzy numbers. The performance method is analyzed in terms for four gas ratio (IEC 60599) signature as input data of FRSN P systems. Test case results evaluate that the proposals method for power transformer fault diagnosis can significantly improve the diagnosis accuracy power transformer.展开更多
Morlet wavelet is suitable to extract the impulse components of mechanical fault signals. And thus its continuous wavelet transform （CWT） has been successfully used in the field of fault diagnosis. The principle of ...Morlet wavelet is suitable to extract the impulse components of mechanical fault signals. And thus its continuous wavelet transform （CWT） has been successfully used in the field of fault diagnosis. The principle of scale selection in CWT is discussed. Based on genetic algorithm, an optimization strategy for the waveform parameters of the mother wavelet is proposed with wavelet entropy as the optimization target. Based on the optimized waveform parameters, the wavelet scalogram is used to analyze the simulated acoustic emission （AE） signal and real AE signal of rolling bearing. The results indicate that the proposed method is useful and efficient to improve the quality of CWT.展开更多
The original fault data of oil immersed transformer often contains a large number of unnecessary attributes,which greatly increases the elapsed time of the algorithm and reduces the classification accuracy,leading to ...The original fault data of oil immersed transformer often contains a large number of unnecessary attributes,which greatly increases the elapsed time of the algorithm and reduces the classification accuracy,leading to the rise of the diagnosis error rate.Therefore,in order to obtain high quality oil immersed transformer fault attribute data sets,an improved imperialist competitive algorithm was proposed to optimize the rough set to discretize the original fault data set and the attribute reduction.The feasibility of the proposed algorithm was verified by experiments and compared with other intelligent algorithms.Results show that the algorithm was stable at the 27th iteration with a reduction rate of 56.25%and a reduction accuracy of 98%.By using BP neural network to classify the reduction results,the accuracy was 86.25%,and the overall effect was better than those of the original data and other algorithms.Hence,the proposed method is effective for fault attribute reduction of oil immersed transformer.展开更多
As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reape...As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reaped. However, these achievements were mostly confined to an individual orogenic belt and the study of the mutual relationship among the three orogenic belts was obliged to depend on comparative studies. Different views were produced therefrom. The material composition and structural features of the junction region show that there are several epicontinental and intracontinental transform faults developed in different periods. Restricted by these transform faults, the large-scale lateral movements and, as a consequence, complicated magmatism and tectonic deformation took place in the orogenic belts. According to these features, the authors put forward a three-stage junction and evolution model and point out that there is not a single junction zone traversing from west to east but that the three orogenic belts have been joined progressively by the epicontinental and intracontinental transform faults.展开更多
The 3-D geometry of the seismicity in Hindu Kush-Pamir--western China region has been defined by seismic records for 1975-1999 from the National Earthquake Information Center, the U.S. Geological Survey, and over 16,0...The 3-D geometry of the seismicity in Hindu Kush-Pamir--western China region has been defined by seismic records for 1975-1999 from the National Earthquake Information Center, the U.S. Geological Survey, and over 16,000 relocated earthquakes since 1975 recorded by the Xinjiang seismic network of China. The results show that most Ms≥ 5.0 hypocenters in the area are confined to a major intracontinental seismic shear zone （MSSZ）. The MSSZ, which dips southwards in Pamir has a north- dipping counterpart in the Hindu Kush to the west; the two tectonic realms are separated by the sinistral Chaman transform fault of the India-Asia collisional zone. We demonstrate that the MSSZ constitutes the upper boundary of a south-dipping, actively subducting Pamir continental plate. Three seismic concentrations are recognized just above the Pamir MSSZ at depths between 45-65 km, 95-120 km, and 180-220 km, suggesting different structural relationships where each occurs. Results from focal mechanism solutions in all three seismological concentrations show orientations of the principal maximum stress to be nearly horizontal in an NNW-SSE direction. The south-dipping Pamir subduction slab is wedge-shaped with a wide upper top and a narrow deeper bottom; the slab has a gentle angle of dip in the upper part and steeper dips in the lower part below an elbow depth of ca. 80--120 km. Most of the deformation related to the earthquakes occurs within the hanging wall of the subducting Pamir slab. Published geologic data and repeated GPS measurements in the Pamir document a broad supra-subduc- tion, upper crustal zone of evolving antithetic （i.e. north-dipping） back-thrusts that contribute to northsouth crustal shortening and are responsible for exhumation of some ultrahigh-pressure rocks formed during earlier Tethyan plate convergence. An alternating occurrence in activity of Pamir and Chaman seismic zones indicates that there is interaction between strike-slip movement of the Chaman transform fault system and deep-subduction of the Pamir earthquake zone. Pamir subdnction-related seismicity becomes shallower in depth with increasing distance east of the transform fault. Therefore, sinistral movement of the Chaman transform fault appears to be influencing continental deep-subduction in the Pamir region and may provide an explanation for the unusual south-dipping geometry of the intracontinental Pamir plate.展开更多
3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the se...3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the sea, and coincides with the structure of crystalline basement. The essential difference in tectonics between the East China Sea and the Yellow Sea mainly lies in that the velocity structures of their lower crust and upper mantle are identical to those of South China and North China respectively. In the upper mantle there exists a high-velocity zone with a nearly EW strike from the Hangzhou Bay, China, to the Tokara Channel, Japan, along about the latitude of 30°N. It is found that between the East China Sea and the Yellow Sea there are systematical differences in geomorphology, geology, seismicity, heat flow, quality factor and gravity and aeromagnetic anomalies, which is related to both left-lateral shear dislocation and right-lateral tear of the Benioff zone from the Hangzhou Bay to the Tokara Channel.It is inferred that the East China Sea was formed by Cenozoic back-arc extension. The boundary between the North China and South China crustal blocks stretches along the southern piedmont of Mts. Daba-Dabie-Hangzhou Bay-Tokara Channel, and the subduction zone at the Okinawa trench is the eastern boundary of the South China crustal block. The movements of the Pacific plate, Indian plate and upper mantle rather than the Philippine plate subduction have played a dominant role for the modern tectonic movements in East Asia.展开更多
Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is s...Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is still insufficient, which constrains the oil and gas exploration in deep-water areas. Based on comprehensive data of magnetic anomalies, seismic survey, and drilling, this study determines the structure characteristics of the Scotian Basin and its hydrocarbon accumulation conditions in deep waters and evaluates the deep-water hydrocarbon exploration potential. The transform faults and basement structures in the northern basin control the sedimentary framework showing thick strata in east and thin strata in west of the basin. The bowl-shaped depression formed by thermal subsidence during the transitional phase and the confined environment (micro basins) caused by salt tectonics provide favorable conditions for the development of source rocks during the depression stage (also referred to as the depression period sequence) of the basin. The progradation of large shelf-margin deltas during the drift phase and steep continental slope provide favorable conditions for the deposition of slope-floor fans on continental margins of the basin. Moreover, the source-reservoir assemblage comprising the source rocks within the depression stage and the turbidite sandstones on the continental margin in the deep waters may form large deep-water turbidite sandstone reservoirs. This study will provide a valuable reference for the deep-water hydrocarbon exploration in the Scotian Basin.展开更多
The plate boundary between Balochistan and Indus basins is found on the position where Western Indus Suture and Chaman Transform fault converge in the south (Uthal-Bela-Ornach-Nal-Basima). From Basima to northward the...The plate boundary between Balochistan and Indus basins is found on the position where Western Indus Suture and Chaman Transform fault converge in the south (Uthal-Bela-Ornach-Nal-Basima). From Basima to northward the both structures bifurcate and separate more than 50 km in the Zhob region, the Chaman Transform fault lies in the west as straight way in flysh and slates of Balochistan basin, and Western Indus suture lies in the east mostly straight and wide (more than 20 km wide) galaxy way like belt (gentle wavy in the central portion from Quetta to Zhob). Plate boundary between Balochistan basin and Indus basin lies in the Western Indus suture. The both structures are about 1000 - 1500 km trends northward. The northward bending of strikes in the southern Balochistan basin (from Arabian sea to Kharan) on the western flank of Chaman transform fault and dragging of Kharan limestones revealed left lateral strike slip fault. The structures of Balochistan basin are mostly imbricated while the structure of Indus basin is mostly folded. Different basins in Pakistan yielded dinosaurs and diverse Mesozoic vertebrates like poripuchian titanosaurian sauropods, vitakrisaurid abelisaurian theropods, induszalimids, sulaimanisuchid and mithsaraikistanid mesoeucrocodiles, saraikisaurid pterosaurs, wasaibpanchid bird, madtsoiid snake, zahrisaurid plesiosaur and some fishes. From Pakistan 10 titanosaurs were named while from India 5 titanosaurs were named and discussed here. The updated assessment for the attribution of bones to Jainosaurus septentrionalis resulted the braincase its type or in other case braincase and scapula referable to Isisaurus colberti matching its long articular surface for coracoid of distal scapula. Key bones which were previously referred to Jainosaurus septentrionalis belong to mostly Gspsaurus pakistani and Balochisaurus malkani (stocky titanosaurs) and a few bones to Isisaurus colberti and Pakisaurus balochistani (slender titanosaurs).展开更多
The oceanic transform fault(OTF)is one of the three types of plate boundaries.It provides an important channel for the exchange of material and energy within the Earth's interior,which is significant for understan...The oceanic transform fault(OTF)is one of the three types of plate boundaries.It provides an important channel for the exchange of material and energy within the Earth's interior,which is significant for understanding global plate tectonics.In recent years,substantial progress has been made in the study of OTFs,including their morphology,crustal accretion mode,stress and strain state,brittle-ductile deformation structures,and segmentation and symmetry of seismicity.The combined effects of magmatism and tectonism shape the morphology and structure of OTF:the spreading rate and the age offsets reflect the thermal structure of the OTF,and thus affect the intensity of magmatism;meanwhile,the stress within the lithosphere and plate motion control the tectonic features and formation of faults.Three-dimensional dynamic models have demonstrated that increased magmatism at mid-ocean ridges destabilizes the fault,thereby facilitating the dynamic evolution of the OTF.Moreover,the maximum depth of earthquakes on OTF is controlled by the thermal structure of the lithosphere,which is crucial for characterizing the frictional properties of faults and understanding their seismic behaviors.Based on recent comprehensive research findings,this paper reviews the tectonic features,three-dimensional morphological structure,and lithospheric thermal structure of OTF,and discusses important scientific issues,including the magmatic-tectonic co-evolution and geodynamic mechanisms of OTF.Future research will combine high-resolution observations and theoretical simulations to further elucidate the processes and mechanisms of OTF,providing important advances to global plate tectonic theory.展开更多
This study provides a comprehensive analysis of the transformational role and dynamic mechanisms in arc-shaped subduction orogenic belts,with a specific focus on their manifestations in regions such as the Mediterrane...This study provides a comprehensive analysis of the transformational role and dynamic mechanisms in arc-shaped subduction orogenic belts,with a specific focus on their manifestations in regions such as the Mediterranean and the Caribbean.Current research highlights the control exerted by the negative buoyancy of subducting oceanic plates on subduction rates and their role in driving slab rollback.The feedback effects between trench retreat and tectonic transformation are identified as key mechanisms contributing to the curvature of orogenic belts.Simulation results indicate that the timing and distance of back-arc spreading center jumps in curved subduction zones are governed by the ratio of strength between transform faults and the overriding plate.Gravity-driven forces from subducting slabs are the primary drivers of arc curvature,tectonic transformations along subduction zones,the formation of transform faults,slab tearing,and even the rollback-driven invasion of curved subduction zones into Atlantic-type oceans.Geological evidence reveals that the development of transtensional or transpressional deformation in arc-shaped subduction orogenic belts results from the complex interactions between slab-rollbacked subduction and tectonic transformation within the overriding plate.This research not only enhances our understanding of the dynamics of global arc-shaped subduction orogenic belts but also underscores the importance of integrating geological observations with numerical simulations to unveil the complexities of arc-shaped subduction dynamic systems.展开更多
Earthquakes are among the most severe natural hazards that affect different regions of the globe.Generally,earthquakes take place on geologic weakness zones of the earth,especially faults.In Jordan and the Levant coun...Earthquakes are among the most severe natural hazards that affect different regions of the globe.Generally,earthquakes take place on geologic weakness zones of the earth,especially faults.In Jordan and the Levant countries,active faults are abundant,especially,the Dead Sea Transform Fault and its offspring faults resulting in the formation of the Jordan Rift Valley.The Dead Sea Trans-form Fault is the main active tectonic feature in the region that builds the tec-tonic boundary between the Arabian and African plates.The recent earthquake of 2023 in Türkiye and Syria,which left behind tens of thousands of casualties and enormous damage,scared the inhabitants in Jordan who were afraid that such earthquakes might hit in Jordan.This paper discusses the main geologic structures in Jordan and its immediate surroundings,along which earthquakes have taken place in the past,and how the genetics of the geologic structures relate to the earthquakes and their magnitudes.The study concludes that the fractured tectonics and tensional faulting of Jordan characterized by short fault extensions including the Dead Sea Transform Fault,which,on its eastern side,is divided into several east-west striking blocks,seem to accommodate tectonic movements on a block size,and that does not allow for the accumulation of tectonic stresses to produce large earthquakes.Earthquakes during the last cen-tury indicate that only along the Jordan Rift Valley earthquakes of intermediate magnitudes have taken place,but along all other fault zones,only very mild earthquakes have taken place and are expected,in the future to release tectonic pressures in the same mild form.展开更多
The N-S trending Xiaojiang fault zone and the NW-SE trending Qujiang-Shiping fault zone are adjacent active fault systems and seismogenic zones associated with strong and major earthquakes in Yunnan, China. To underst...The N-S trending Xiaojiang fault zone and the NW-SE trending Qujiang-Shiping fault zone are adjacent active fault systems and seismogenic zones associated with strong and major earthquakes in Yunnan, China. To understand the interaction of the two fault systems, and its probable influence on earthquake occurrences, this paper conducts a synthetic study based on data of active tectonics, historical earthquakes, relocated small earthquakes, GPS station velocities and focal mechanism resolutions. The study makes several conclusions. （1） The active southward motion of the western side of the Xiaojiang fault zone （i.e. the side of the Sichuan-Yunnan block） has a persistent and intensive effect on the Qujiang-Shiping fault zone. The later fault zone has absorbed and transformed the southward motion of the western side of the former fault zone through dextral strike-slip/sheafing as well as transverse shortening/thrusting. （2） Along the Xiaojiang fault zone, the present sinistral strike-slip/sheafing rate decreases from 10 and 8 mm/a on the northern, central and central-southern segments to 4 mm/a on the southern segment. The decreased rate has been adjusted in the area along and surrounding the Qujiang-Shiping fault zone through reverse-dextral faulting and distributed sheafing and shortening. （3） The tectonic-dynamic relation between the Xiaojiang fault zone and the Qujiang-Shiping fault zone is also manifested by a close correlation of earthquake occurrences on the two fault zones. From 1500 to 1850 a sequence of strong and major earthquakes occurred along the Xiaojiang fault zone and its northern neighbor, the Zemuhe fault zone, which was characterized by gradually accelerating strain release, gradually shortening intervals between M≥7 events, and major releases occurring in the mid to later stages of the sequence. As a response to this sequence, after an 88-year delay, another sequence of 383 years （from 1588 to 1970） of strong and major earthquakes occurred on the Qujiang-Shiping fault zone, and had the same features in accelerating strain release and its temporal course. （4） Since there has been no M≥7 event for 177 years on the Xiaojiang fault zone, the potential risk of a strong or major earthquake occurring on this fault zone in the future should be noticed and studied further.展开更多
The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we revie...The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone(YTSZ) between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.展开更多
基金The foundation of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0205the National Natural Science Foundation of China under contract Nos 41976064,41890813,41976066,91958211,and 41706056+4 种基金the scholarship of China Scholarship Councilthe foundations of the Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDY-SSW-DQC005,133244KYSB20180029,and 131551KYSB20200021the National Key Research and Development Program of China under contract Nos 2018YFC0309800 and 2018YFC0310105the Foundation of the China Ocean Mineral Resources Research and Development Association under contract No.DY135-S2-1-04the Guangdong Basic and Applied Basic Research Foundation under contract No.2021A1515012227。
文摘We quantified the systematic variations in global transform fault morphology,revealing a first-order dependence on the spreading rate.(1)The average age offset of both the full transform and transform sub-segments decrease with increasing spreading rate.(2)The average depth of both the transform valley and adjacent ridges are smaller in the fast compared to the slow systems,reflecting possibly density anomalies associated with warmer mantle at the fast systems and rifting at the slow ridges.However,the average depth difference between the transform valley and adjacent ridges is relatively constant from the fast to slow systems.(3)The nodal basin at a ridge-transform intersection is deeper and dominant at the ultraslow and slow systems,possibly reflecting a lower magma supply and stronger viscous resistance to mantle upwelling near a colder transform wall.In contrast,the nodal high,is most prominent in the fast,intermediate,and hotspot-influenced systems,where robust axial volcanic ridges extend toward the ridge-transform intersection.(4)Statistically,the average transform valley is wider at a transform system of larger age offset,reflecting thicker deforming plates flanking the transform fault.(5)The maximum magnitude of the transform earthquakes increases with age offset owing to an increase in the seismogenic area.Individual transform faults also exhibit significant anomalies owing to the complex local tectonic and magmatic processes.
基金Supported by the State Key Program of National Natural Science of China(No.42330308)the Project of Donghai Laboratory(No.DH-2022ZY0005)+4 种基金the Scientific Research Fund of the Second Institute of OceanographyMinistry of Natural Resources(No.QHXZ2301)the National Science Foundation for Distinguished Young Scholars of China(No.42025601)for Young Scientists of China(No.41906064)the Zhejiang Provincial Natural Science Foundation of China(No.LDQ24D060001)。
文摘Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the oceanic lithosphere remains poorly understood.The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an indepth view of the underlying detailed seismic structures,contributing to understanding geodynamic processes within the oceanic lithosphere.Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃isotherm.However,this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults.Several mechanisms have been proposed to explain these deep events,and we suggest that local geodynamic processes(e.g.,magma supply,mylonite shear zone,longlived faults,hydrothermal vents,etc.)likely play a more important role than previously thought.
基金supported by the National Natural Science Foundation of China(Grant Nos.42330310,42442012)。
文摘Large strike-slip faults play a crucial role in regulating the geometry and kinematics of the solid Earth's outer lithospheric plates and the structural deformation of internal continents.They not only control the geometric structures,motion properties,and direction of the lithospheric plates,but also regulate the complex tectonic stress field and strain state caused by differential motion among multiple blocks within the continent,maintaining the relative stability of the overall stress state of the lithosphere on the Earth's surface.According to the nature and significance of geotectonic structures,strike-slip faults can be divided into interplate types and intraplate tectonic types.Interplate strike-slip faults are transform faults,including oceanic transform faults and continental transform faults.Intraplate strike-slip faults can be divided into continental transfer faults and intraplate transcurrent faults.During the lateral movement of lithospheric plates along the Earth's surface,transform faults adjust the differences in the nature,direction,and rate of movement between different plates.Meanwhile,continental transfer faults and intraplate transcurrent faults adjust the location,nature,style,and differential stress of intraplate tectonic deformation.Strike-slip faults of varying types and scales interact in different ways to maintain the dynamic balance of matter and energy within Earth's lithospheric plates.Based on the concepts,tectonic significance,and recent research advances of strike-slip faults and classical transform faults,this paper summarizes the latest classification of strike-slip faults and their corresponding tectonic implications.It also updates the definitions,geometric characteristics,and kinematic features of oceanic transform faults,continental transform faults,continental transfer faults,and intraplate transcurrent faults.Through typical global examples,this paper comprehensively analyzes the deep structure,structural geometry and kinematic characteristics,evolution process,geological significance,and seismic hazards of different types of strike-slip faults.Furthermore,the frontier science issue and research strategies for the study of oceanic transform faults,continental transfer faults,and intraplate transcurrent faults are summarized as well.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3003701)the National Natural Science Foundation of China(Grant No.42274061)。
文摘Transform faults represent one of the three primary types of plate boundaries in plate tectonics theory and constitute an essential component of this framework.In general,they are classified into oceanic and continental transform faults based on the nature of their separated plates.Owing to significant differences in properties between continental and oceanic lithospheres,continental transform faults exhibit more complex structures than their oceanic counterparts.Continental transform faults are strike-slip boundaries where stress and strain are highly concentrated.They typically extend for hundreds to thousands of kilometers and have experienced tens to hundreds of kilometers of strike-slip displacement.These faults may appear as a single master fault or as complex fault systems with multiple branches.Their deep structures and deformation patterns at varying depths offer critical insights into the structure and rheological behavior of the continental lithosphere.Imaging fine-scale structures of continental transform faults via geophysical methods is crucial for understanding their nature and evolution.Seismic anisotropy results provide key constraints on their deep deformation characteristics.This paper reviews geophysical studies from typical continental transform fault regions and investigates their deep structure and deformation mechanisms by integrating geological and geodetic observations.Although these fault systems are structurally diverse,several common features emerge.(1)Nearly all continental transform faults cut through the entire crust and extend into the upper mantle,with significant seismic anisotropy observed within the fault zones.(2)Regardless of whether the fault is a single narrow structure or a branching system,uppercrustal segments typically form narrow zones of strain concentration where brittle friction accommodates slip and seismicity is concentrated.The shear zone broadens with depth,reaching tens of kilometers in width within the lithospheric mantle.(3)The width of a continental transform fault correlates with the nature of the lithosphere it cross-cuts.Narrow shear zones form in rigid and ancient lithosphere,otherwise,broader distributed deformation occurs.(4)Non-strike-slip components(compression or tension)significantly influence fault zone complexity.Recent ocean drilling programs have advanced understanding of oceanic transform faults,yet knowledge of continental transform fault structure and evolution remains limited.Advances in seismic imaging and observational techniques will enable higher-resolution characterization of these faults,providing new constraints on their seismic behavior and earthquake migration patterns.
文摘Deca</span><span style="font-family:Verdana;">dal forerunning seismic activity is examined for very large, shall</span><span style="font-family:Verdana;">ow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seism</span><span style="font-family:Verdana;">ic slip as determined by others using geodetic, mapping of surf</span><span style="font-family:Verdana;">ace faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep</span></span><span style="font-family:""> </span><span style="font-family:Verdana;"> forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones.
文摘The back propagation (BP)-based artificial neural nets (ANN) can identify complicated relationships among dissolved gas contents in transformer oil and corresponding fault types, using the highly nonlinear mapping nature of the neural nets. An efficient BP-ALM (BP with Adaptive Learning Rate and Momentum coefficient) algorithm is proposed to reduce the training time and avoid being trapped into local minima, where the learning rate and the momentum coefficient are altered at iterations. We developed a system of transformer fault diagnosis based on Dissolved Gases Analysis (DGA) with a BP-ALM algorithm. Training patterns were selected from the results of a Refined Three-Ratio method (RTR). Test results show that the system has a better ability of quick learning and global convergence than other methods and a superior performance in fault diagnosis compared to convectional BP-based neural networks and RTR.
文摘This paper presents an intelligent technique to fault diagnosis of power transformers dissolved and free gas analysis (DGA). Fuzzy Reasoning Spiking neural P systems (FRSN P systems) as a membrane computing with distributed parallel computing model is powerful and suitable graphical approach model in fuzzy diagnosis knowledge. In a sense this feature is required for establishing the power transformers faults identifications and capturing knowledge implicitly during the learning stage, using linguistic variables, membership functions with “low”, “medium”, and “high” descriptions for each gas signature, and inference rule base. Membership functions are used to translate judgments into numerical expression by fuzzy numbers. The performance method is analyzed in terms for four gas ratio (IEC 60599) signature as input data of FRSN P systems. Test case results evaluate that the proposals method for power transformer fault diagnosis can significantly improve the diagnosis accuracy power transformer.
基金This project is supported by National Natural Science Foundation of China (No. 50105007)Program for New Century Excellent Talents in University, China.
文摘Morlet wavelet is suitable to extract the impulse components of mechanical fault signals. And thus its continuous wavelet transform （CWT） has been successfully used in the field of fault diagnosis. The principle of scale selection in CWT is discussed. Based on genetic algorithm, an optimization strategy for the waveform parameters of the mother wavelet is proposed with wavelet entropy as the optimization target. Based on the optimized waveform parameters, the wavelet scalogram is used to analyze the simulated acoustic emission （AE） signal and real AE signal of rolling bearing. The results indicate that the proposed method is useful and efficient to improve the quality of CWT.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51504085)the Natural Science Foundation for Returness of Heilongjiang Province of China(Grant No.LC2017026).
文摘The original fault data of oil immersed transformer often contains a large number of unnecessary attributes,which greatly increases the elapsed time of the algorithm and reduces the classification accuracy,leading to the rise of the diagnosis error rate.Therefore,in order to obtain high quality oil immersed transformer fault attribute data sets,an improved imperialist competitive algorithm was proposed to optimize the rough set to discretize the original fault data set and the attribute reduction.The feasibility of the proposed algorithm was verified by experiments and compared with other intelligent algorithms.Results show that the algorithm was stable at the 27th iteration with a reduction rate of 56.25%and a reduction accuracy of 98%.By using BP neural network to classify the reduction results,the accuracy was 86.25%,and the overall effect was better than those of the original data and other algorithms.Hence,the proposed method is effective for fault attribute reduction of oil immersed transformer.
文摘As the main part of the “central mountain system” in the continent of China, the Qinling, Qilian and Kunlun orogenic belts have been comprehensively and deeply studied since the 1970s and rich fruits have been reaped. However, these achievements were mostly confined to an individual orogenic belt and the study of the mutual relationship among the three orogenic belts was obliged to depend on comparative studies. Different views were produced therefrom. The material composition and structural features of the junction region show that there are several epicontinental and intracontinental transform faults developed in different periods. Restricted by these transform faults, the large-scale lateral movements and, as a consequence, complicated magmatism and tectonic deformation took place in the orogenic belts. According to these features, the authors put forward a three-stage junction and evolution model and point out that there is not a single junction zone traversing from west to east but that the three orogenic belts have been joined progressively by the epicontinental and intracontinental transform faults.
基金supported by the Major State Basic Research Development Program grants 2008DFA20700 and 2008CB425703
文摘The 3-D geometry of the seismicity in Hindu Kush-Pamir--western China region has been defined by seismic records for 1975-1999 from the National Earthquake Information Center, the U.S. Geological Survey, and over 16,000 relocated earthquakes since 1975 recorded by the Xinjiang seismic network of China. The results show that most Ms≥ 5.0 hypocenters in the area are confined to a major intracontinental seismic shear zone （MSSZ）. The MSSZ, which dips southwards in Pamir has a north- dipping counterpart in the Hindu Kush to the west; the two tectonic realms are separated by the sinistral Chaman transform fault of the India-Asia collisional zone. We demonstrate that the MSSZ constitutes the upper boundary of a south-dipping, actively subducting Pamir continental plate. Three seismic concentrations are recognized just above the Pamir MSSZ at depths between 45-65 km, 95-120 km, and 180-220 km, suggesting different structural relationships where each occurs. Results from focal mechanism solutions in all three seismological concentrations show orientations of the principal maximum stress to be nearly horizontal in an NNW-SSE direction. The south-dipping Pamir subduction slab is wedge-shaped with a wide upper top and a narrow deeper bottom; the slab has a gentle angle of dip in the upper part and steeper dips in the lower part below an elbow depth of ca. 80--120 km. Most of the deformation related to the earthquakes occurs within the hanging wall of the subducting Pamir slab. Published geologic data and repeated GPS measurements in the Pamir document a broad supra-subduc- tion, upper crustal zone of evolving antithetic （i.e. north-dipping） back-thrusts that contribute to northsouth crustal shortening and are responsible for exhumation of some ultrahigh-pressure rocks formed during earlier Tethyan plate convergence. An alternating occurrence in activity of Pamir and Chaman seismic zones indicates that there is interaction between strike-slip movement of the Chaman transform fault system and deep-subduction of the Pamir earthquake zone. Pamir subdnction-related seismicity becomes shallower in depth with increasing distance east of the transform fault. Therefore, sinistral movement of the Chaman transform fault appears to be influencing continental deep-subduction in the Pamir region and may provide an explanation for the unusual south-dipping geometry of the intracontinental Pamir plate.
基金The study (Project No. 85078) was supported by the Joint Foundation of Seismic Science.
文摘3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the sea, and coincides with the structure of crystalline basement. The essential difference in tectonics between the East China Sea and the Yellow Sea mainly lies in that the velocity structures of their lower crust and upper mantle are identical to those of South China and North China respectively. In the upper mantle there exists a high-velocity zone with a nearly EW strike from the Hangzhou Bay, China, to the Tokara Channel, Japan, along about the latitude of 30°N. It is found that between the East China Sea and the Yellow Sea there are systematical differences in geomorphology, geology, seismicity, heat flow, quality factor and gravity and aeromagnetic anomalies, which is related to both left-lateral shear dislocation and right-lateral tear of the Benioff zone from the Hangzhou Bay to the Tokara Channel.It is inferred that the East China Sea was formed by Cenozoic back-arc extension. The boundary between the North China and South China crustal blocks stretches along the southern piedmont of Mts. Daba-Dabie-Hangzhou Bay-Tokara Channel, and the subduction zone at the Okinawa trench is the eastern boundary of the South China crustal block. The movements of the Pacific plate, Indian plate and upper mantle rather than the Philippine plate subduction have played a dominant role for the modern tectonic movements in East Asia.
基金supported by the National Science and Technology Major Project of China(2016ZX05033)the Project of SINOPEC Science and Technology Department(P19021-2)the Basic Prospective Research Project of SINOPEC(P22214-2).
文摘Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is still insufficient, which constrains the oil and gas exploration in deep-water areas. Based on comprehensive data of magnetic anomalies, seismic survey, and drilling, this study determines the structure characteristics of the Scotian Basin and its hydrocarbon accumulation conditions in deep waters and evaluates the deep-water hydrocarbon exploration potential. The transform faults and basement structures in the northern basin control the sedimentary framework showing thick strata in east and thin strata in west of the basin. The bowl-shaped depression formed by thermal subsidence during the transitional phase and the confined environment (micro basins) caused by salt tectonics provide favorable conditions for the development of source rocks during the depression stage (also referred to as the depression period sequence) of the basin. The progradation of large shelf-margin deltas during the drift phase and steep continental slope provide favorable conditions for the deposition of slope-floor fans on continental margins of the basin. Moreover, the source-reservoir assemblage comprising the source rocks within the depression stage and the turbidite sandstones on the continental margin in the deep waters may form large deep-water turbidite sandstone reservoirs. This study will provide a valuable reference for the deep-water hydrocarbon exploration in the Scotian Basin.
文摘The plate boundary between Balochistan and Indus basins is found on the position where Western Indus Suture and Chaman Transform fault converge in the south (Uthal-Bela-Ornach-Nal-Basima). From Basima to northward the both structures bifurcate and separate more than 50 km in the Zhob region, the Chaman Transform fault lies in the west as straight way in flysh and slates of Balochistan basin, and Western Indus suture lies in the east mostly straight and wide (more than 20 km wide) galaxy way like belt (gentle wavy in the central portion from Quetta to Zhob). Plate boundary between Balochistan basin and Indus basin lies in the Western Indus suture. The both structures are about 1000 - 1500 km trends northward. The northward bending of strikes in the southern Balochistan basin (from Arabian sea to Kharan) on the western flank of Chaman transform fault and dragging of Kharan limestones revealed left lateral strike slip fault. The structures of Balochistan basin are mostly imbricated while the structure of Indus basin is mostly folded. Different basins in Pakistan yielded dinosaurs and diverse Mesozoic vertebrates like poripuchian titanosaurian sauropods, vitakrisaurid abelisaurian theropods, induszalimids, sulaimanisuchid and mithsaraikistanid mesoeucrocodiles, saraikisaurid pterosaurs, wasaibpanchid bird, madtsoiid snake, zahrisaurid plesiosaur and some fishes. From Pakistan 10 titanosaurs were named while from India 5 titanosaurs were named and discussed here. The updated assessment for the attribution of bones to Jainosaurus septentrionalis resulted the braincase its type or in other case braincase and scapula referable to Isisaurus colberti matching its long articular surface for coracoid of distal scapula. Key bones which were previously referred to Jainosaurus septentrionalis belong to mostly Gspsaurus pakistani and Balochisaurus malkani (stocky titanosaurs) and a few bones to Isisaurus colberti and Pakisaurus balochistani (slender titanosaurs).
基金supported by the Natural Science Foundation of Guangdong Province(Grant No.2024B1515020100)the National Natural Science Foundation of China(Grant Nos.42306093,42406071,42306073,42206070)。
文摘The oceanic transform fault(OTF)is one of the three types of plate boundaries.It provides an important channel for the exchange of material and energy within the Earth's interior,which is significant for understanding global plate tectonics.In recent years,substantial progress has been made in the study of OTFs,including their morphology,crustal accretion mode,stress and strain state,brittle-ductile deformation structures,and segmentation and symmetry of seismicity.The combined effects of magmatism and tectonism shape the morphology and structure of OTF:the spreading rate and the age offsets reflect the thermal structure of the OTF,and thus affect the intensity of magmatism;meanwhile,the stress within the lithosphere and plate motion control the tectonic features and formation of faults.Three-dimensional dynamic models have demonstrated that increased magmatism at mid-ocean ridges destabilizes the fault,thereby facilitating the dynamic evolution of the OTF.Moreover,the maximum depth of earthquakes on OTF is controlled by the thermal structure of the lithosphere,which is crucial for characterizing the frictional properties of faults and understanding their seismic behaviors.Based on recent comprehensive research findings,this paper reviews the tectonic features,three-dimensional morphological structure,and lithospheric thermal structure of OTF,and discusses important scientific issues,including the magmatic-tectonic co-evolution and geodynamic mechanisms of OTF.Future research will combine high-resolution observations and theoretical simulations to further elucidate the processes and mechanisms of OTF,providing important advances to global plate tectonic theory.
基金funded by the National Natural Science Foundation of China(Grant No.42241201)the Seed Fund for the Deep-Time Digital Earth International Science Program(Grant No.GJC03-2023-002)the Frontier Science Center for Deep-Time Digital Earth at Central Universities(Grant No.2652023001)。
文摘This study provides a comprehensive analysis of the transformational role and dynamic mechanisms in arc-shaped subduction orogenic belts,with a specific focus on their manifestations in regions such as the Mediterranean and the Caribbean.Current research highlights the control exerted by the negative buoyancy of subducting oceanic plates on subduction rates and their role in driving slab rollback.The feedback effects between trench retreat and tectonic transformation are identified as key mechanisms contributing to the curvature of orogenic belts.Simulation results indicate that the timing and distance of back-arc spreading center jumps in curved subduction zones are governed by the ratio of strength between transform faults and the overriding plate.Gravity-driven forces from subducting slabs are the primary drivers of arc curvature,tectonic transformations along subduction zones,the formation of transform faults,slab tearing,and even the rollback-driven invasion of curved subduction zones into Atlantic-type oceans.Geological evidence reveals that the development of transtensional or transpressional deformation in arc-shaped subduction orogenic belts results from the complex interactions between slab-rollbacked subduction and tectonic transformation within the overriding plate.This research not only enhances our understanding of the dynamics of global arc-shaped subduction orogenic belts but also underscores the importance of integrating geological observations with numerical simulations to unveil the complexities of arc-shaped subduction dynamic systems.
文摘Earthquakes are among the most severe natural hazards that affect different regions of the globe.Generally,earthquakes take place on geologic weakness zones of the earth,especially faults.In Jordan and the Levant countries,active faults are abundant,especially,the Dead Sea Transform Fault and its offspring faults resulting in the formation of the Jordan Rift Valley.The Dead Sea Trans-form Fault is the main active tectonic feature in the region that builds the tec-tonic boundary between the Arabian and African plates.The recent earthquake of 2023 in Türkiye and Syria,which left behind tens of thousands of casualties and enormous damage,scared the inhabitants in Jordan who were afraid that such earthquakes might hit in Jordan.This paper discusses the main geologic structures in Jordan and its immediate surroundings,along which earthquakes have taken place in the past,and how the genetics of the geologic structures relate to the earthquakes and their magnitudes.The study concludes that the fractured tectonics and tensional faulting of Jordan characterized by short fault extensions including the Dead Sea Transform Fault,which,on its eastern side,is divided into several east-west striking blocks,seem to accommodate tectonic movements on a block size,and that does not allow for the accumulation of tectonic stresses to produce large earthquakes.Earthquakes during the last cen-tury indicate that only along the Jordan Rift Valley earthquakes of intermediate magnitudes have taken place,but along all other fault zones,only very mild earthquakes have taken place and are expected,in the future to release tectonic pressures in the same mild form.
基金supported by the Special Funds for Research of Earthquake Science (Grant No. 200708035)the Special Project M7 of China Earthquake Administration
文摘The N-S trending Xiaojiang fault zone and the NW-SE trending Qujiang-Shiping fault zone are adjacent active fault systems and seismogenic zones associated with strong and major earthquakes in Yunnan, China. To understand the interaction of the two fault systems, and its probable influence on earthquake occurrences, this paper conducts a synthetic study based on data of active tectonics, historical earthquakes, relocated small earthquakes, GPS station velocities and focal mechanism resolutions. The study makes several conclusions. （1） The active southward motion of the western side of the Xiaojiang fault zone （i.e. the side of the Sichuan-Yunnan block） has a persistent and intensive effect on the Qujiang-Shiping fault zone. The later fault zone has absorbed and transformed the southward motion of the western side of the former fault zone through dextral strike-slip/sheafing as well as transverse shortening/thrusting. （2） Along the Xiaojiang fault zone, the present sinistral strike-slip/sheafing rate decreases from 10 and 8 mm/a on the northern, central and central-southern segments to 4 mm/a on the southern segment. The decreased rate has been adjusted in the area along and surrounding the Qujiang-Shiping fault zone through reverse-dextral faulting and distributed sheafing and shortening. （3） The tectonic-dynamic relation between the Xiaojiang fault zone and the Qujiang-Shiping fault zone is also manifested by a close correlation of earthquake occurrences on the two fault zones. From 1500 to 1850 a sequence of strong and major earthquakes occurred along the Xiaojiang fault zone and its northern neighbor, the Zemuhe fault zone, which was characterized by gradually accelerating strain release, gradually shortening intervals between M≥7 events, and major releases occurring in the mid to later stages of the sequence. As a response to this sequence, after an 88-year delay, another sequence of 383 years （from 1588 to 1970） of strong and major earthquakes occurred on the Qujiang-Shiping fault zone, and had the same features in accelerating strain release and its temporal course. （4） Since there has been no M≥7 event for 177 years on the Xiaojiang fault zone, the potential risk of a strong or major earthquake occurring on this fault zone in the future should be noticed and studied further.
基金supported by the Chinese Academy of Sciences(Grant No.XDB03010401)the National Key Research and Development Plan(Grant No.2016YFC0600303)National Natural Science Foundation of China(Grant No.41490615)
文摘The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone(YTSZ) between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.
