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Summarizes the developments in geophysics that have led to the concept of the new global tectonics, which attempts to explain such worldwide features as oceanic ridges and trenches, island arcs and young mountain chains, while it develops processes that cause earthquakes, volcanoes and major faulting. Evidence for the hypotheses of continental drift, sea-floor spreading and the role of arc-like structures are presented. (LC)

The South China Block has experienced multiple phases of tectonic deformation since the Middle Jurassic. Understanding this deformation history helps reveal the driving mechanisms responsible and sheds light on the associated magmatism and mineralization. Here, we construct deformable plate tectonic reconstructions for the South China Block from 170 Ma to the present using GPlates. The deformation starts with a NW–SE-oriented shortening phase from 170 to 136 Ma. Subsequently, South China experienced two episodes of extension in the Cretaceous, during 136–118 Ma and 100–80 Ma, respectively. The Cenozoic extension occurred mostly along the southeast continental margin, including the East China Sea Shelf Basin, and rift basins in the northern South China Sea margin and the Taiwan margin segment. The rifting was initiated nearly simultaneously along the continental margin at ~65 Ma and ceased at ~34–30 Ma. The northern portion of the Okinawa Trough started rifting at 15 Ma, while the southern portion rifted in the last few million years. The Luzon Volcanic Arc’ thrusting onto the southeasternmost South China Block since 6.5 Ma caused the still-active Taiwan Orogeny. The predicted accumulated deformation at present-day is characterized by overall shortening onshore with contraction factors mostly between 0.8 and 1 and extension offshore with stretching factors generally between 1 and 2. The Central China Orogen and Taiwan Orogen experienced more intense shortening relative to the interior South China by factors down to 0.6. The Okinawa Trough experienced intense stretching by factors up to 2.5 in its central part. The intraplate deformation in the South China Block is closely related to the subduction of the Izanagi and Pacific plates. The Jurassic and earliest Cretaceous shortening was likely induced by trench advance, and the extension during the Cretaceous and the Cenozoic was mostly driven by subduction retreat.

The sedimentary basin is a basic geological unit in the Earth system: its formation and evolution are controlled mainly by plate tectonics and geodynamics, which have produced a variety of basin types. The development and evolution of various basins depend not only on the tectonic effect of lithospheric plate but also on sublithospheric, and Earth surface actions. Basin classification schemes based on the theories of platform–geosyncline or plate tectonics could neither include all basin types nor reflect the complex processes of basin formation and evolution. From the viewpoint of Earth system, we proposed a new basin classification scheme based on geodynamic mechanism—that is, lithospheric plate, sublithospheric, and Earth surface actions. In our geodynamic classification, we employed a series of geodynamic settings of basin formation and evolution, including the lithospheric plate, sublithospheric, and Earth surface environments, the dynamic regimes of basin formation and evolution, such as tectonic setting (extension, compression and shearing), the thermal processes and gravity effects, the various natures of basin basement and crustal types (continental, oceanic, or transitional crust), and the history of basin sedimentary filling and tectonic paleogeography successively, as the controlling factors for basin classification. This new geodynamic classification scheme highlights both the role of the lithosphere and the effects of the sublithospheric and the Earth surface actions on controlling the basin formation and evolution. The basic dynamic types of basin classification include the prototype basin forming under a single tectonic, thermal, or gravity regime and the superimposed basin as well as residual basin forming under multistage thermal and/or tectonic regimes. Thus, this classification scheme could provide an evolving understanding of lithosphere, crust–mantle interaction, and geodynamic processes as well as of hydrocarbon accumulation and metallogenic mechanisms in sedimentary basins and would help in the synthetic exploration of various resources.

A number of moderate earthquakes occurred in the South China continental edge or coastal area. Several large earthquakes are sparsely distributed along the seismic belt with the northeast direction between the South China and the continental shelf of the South China Sea. Coulomb stress changes of the 1969 Yangjiang main shock (Ms 6.4) with the following events of the 1986 ML 5.4, the 1987 ML 5.4 and the 2004 ML 5.2 in the Yangbian Bay area are studied. The complex stress patterns of the main shock caused by the dextral Pinggang strike-slip fault imported on the planes of the normal fault, strike-slip fault and thrust fault of three events indicate that the distribution of aftershocks mainly located in the areas of positive stress changes and part of aftershocks fall into the stress shadow area due to the reactivity of the local faults. The 1969 Yangjiang event occurred between the intraplate and the broad plate boundary zone setting when we apply on the empirical relationship between the aftershock durations and the fault-loading rate. The intersection fault model is proposed and could explain the stress changes of the Yangjiang earthquake sequences in South China coastal area. The future hazard assessment requires to take account of the stress increase area along the tip of the main shock source fault and off-fault stress increase area.

Cenozoic tectonic evolution in the Tethyan region has greatly changed the landforms and environment of Eurasia, driving the evolution of animals and greatly affecting the diversity patterns of Eurasian animals. By combining the latest Tethyan paleogeographic models and some recently published Eurasian zoological studies, we systematically summarize how tectonic evolution in the Tethyan region has influenced the evolution and diversity patterns of Eurasian animals. The convergence of continental plates, closure of Tethys Sea, and Tethyan sea-level changes have directly affected the composition and spatial distribution of Eurasian animal diversity. The topographic and environmental changes caused by Tethyan tectonics have determined regional animal diversity in Eurasia by influencing animal origin, dispersal, preservation, diversification, and extinction. The ecological transformations resulted in the emergence of new habitats and niches, which promoted animal adaptive evolution, specialization, speciation, and expansion. We highlight that the Cenozoic tectonic evolution of the Tethyan region has been responsible for much of the alteration in Eurasian animal distribution and has been an essential force in shaping organic evolution. Furthermore, we generalize a general pattern that Tethyan geological events are linked with Eurasian animal evolution and diversity dynamics.特提斯海区域新生代以来的构造演化极大地改变了欧亚地区的地貌和环境，推动了欧亚地区的动物演化，并深刻影响了欧亚地区的动物多样性格局。该文通过结合最新的特提斯海区域古地理模型，对近期发表的一系列欧亚地区动物学研究进行系统回顾和总结，详细论述了特提斯海区域新生代以来的构造演化是如何影响欧亚地区动物的演化及多样性格局的：大陆板块的汇聚、特提斯海的闭合以及特提斯海区域海平面变化直接影响了欧亚地区的动物多样性组成和空间分布；海陆变迁引起的区域地理和环境变化，对当地动物的起源、扩散、存留、多样化和灭绝产生了一系列影响，进而决定了欧亚动物的区域多样性格局；生态环境的变化导致了新栖息地和新生态位的出现，促进了欧亚动物的适应性进化、特化、物种形成和扩张。我们强调了特提斯海区域新生代构造演化是欧亚动物分布变化的主要原因，也是驱动欧亚动物演化的重要力量。此外，我们提出了特提斯地质事件与欧亚动物演化和多样性动态相关的一般模式。.

The intraplate stress field distribution is estimated by considering the isotropic elastic properties of the Indian plate using numerical analysis. In most modelling, the intraplate stresses are typically established on applying plate-driving forces to a homogeneous elastic plate. However, a tectonic plate comprises continental and oceanic lithosphere with sedimentary basins, cratons, and fold belts with varying significant differences in elastic properties, which likely affect the magnitude and pattern of stress and deformation. In the present study, the finite element method (FEM)-based software packages ABAQUS is used to simulate the intraplate stress distribution in the plate using a 3D mechanical model incorporating the elastic properties of the 19 geological regions of the Indian subcontinent and oceanic region. FEM models are validated with Indian plate fixed GPS velocities and found to be in reasonable agreement with the plate’s velocity. This study can augment the interpretability of seismic and geological studies. Also, the model can be helpful to perform seismic hazard assessment (using the stress estimated with the FEM model), identify the seismically active zones and collect insight on active intraplate deformation of seismically active regions of the Indian plate by interpreting the strain rate, deformation rate and stress distribution data.

The southwest Iberian Margin (SWIM) hosted a series of tsunamigenic earthquakes. However, strong magnitude earthquakes M > 7.0 are scarce and geological and geophysical evidence suggest that slow deformation occurs on a large area without a discrete plate boundary. The reanalysis of this event is crucial because of its location in a possible transition zone between the diffuse plate boundary and the stable continent regime. The 11 November 1858 earthquake in Setubal, Portugal, with an estimated M ~ 7, ruined a large part of the city and was felt all over Portugal and large parts of the Iberian Peninsula. Earlier studies suggest an epicentre close to the shore, less than 50 km away, and there exists a description of a tsunami in Setubal. We use macroseismic intensities and present a reevaluation of the event parameters: depth, epicentre, magnitude, and fault orientation. We select the candidate faults according to the epicentral area and plate kinematics and use scaling laws for the magnitude range. We use tsunami numerical modelling to check the tsunamigenic potential of the event. Finally, we compute the tsunami propagation and inundation for Setubal for seven candidate scenarios and analyze waveform data obtained at virtual tide gauges. Our results favour an offshore inverse fault compatible with the tsunami observation corresponding to a reverse fault with a 40° strike angle at 13 km depth and a magnitude range of 6.8 ± 0.3.

We present pore-fluid geochemistry and heat-flow data along the SWIM1 fault in the Horseshoe Abyssal Plain (northeastern Atlantic Ocean). The SWIM1 fault is part of the transcurrent plate boundary between Africa and Eurasia and cuts through as much as 5-km-thick sediments overlying >140 Ma oceanic lithosphere. In a number of places, restraining segments (as long as 15 km) of the SWIM1 fault generate anticlines (positive flower structures) that protrude as ∼100-m-high hills above the abyssal plain. Heat flow and gradients of dissolved constituents in pore water are enhanced at these seafloor highs. Transport-reaction modeling confirms that slow advection of deep-seated fluids, depleted in Mg and enriched in Sr and CH4, can explain the observations. The geochemical signature is similar to the one observed at deep-sea mud volcanoes located eastward on the SWIM1 fault. The upward-migrating fluids have interacted with carbonate rocks at maximum 5 km depth, which represent the oldest sedimentary unit on top of the basement. We argue that deep-rooted fluids can generally be mobilized and transported upward along flower structures that formed in restraining-bend segments of long strike-slip faults. Such tectonic settings represent largely unrecognized corridors for mass exchange between lithosphere and ocean.

During the past 541 million years, marine animals underwent three intervals of diversification (early Cambrian, Ordovician, Cretaceous–Cenozoic) separated by nondirectional fluctuation, suggesting diversity-dependent dynamics with the equilibrium diversity shifting through time. Changes in factors such as shallow-marine habitat area and climate appear to have modulated the nondirectional fluctuations. Directional increases in diversity are best explained by evolutionary innovations in marine animals and primary producers coupled with stepwise increases in the availability of food and oxygen. Increasing intensity of biotic interactions such as predation and disturbance may have led to positive feedbacks on diversification as ecosystems became more complex. Important areas for further research include improving the geographic coverage and temporal resolution of paleontological data sets, as well as deepening our understanding of Earth system evolution and the physiological and ecological traits that modulated organismal responses to environmental change.

The geochemical characteristics of mantle degassing observed on the surface of the earth can indicate the origin and migration path of mantle fluids. Compared with the plate boundary tectonic environment, the intraplate tectonic environment does not have a large number of active volcanoes and active faults, and the observation of mantle volatiles in hot spring gas is relatively limited. We selected the Sichuan–Yunnan block to discuss mantle degassing based on the carbon and noble gas isotopes of the spring gases and previous studies on the fault slip rate and geophysical research. A total of five hot spring gas samples (including two free gases and three dissolved gases) were collected from the Sichuan–Yunnan block. Chemical and isotopic compositions were analyzed in N2-dominant hot spring gases. The 3He/4He ratio (0.068–0.541 Ra) indicates the occurrence of mantle-derived helium throughout the Sichuan–Yunnan block, which has been diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium in the study areas ranges from 0.74 to 5.67%. The lower proportion of mantle-derived helium in YNWQ and HGWQ than that in other spring gases near the Jinghe-Qinghe fault may be caused by the smaller scale of fault around YNWQ and HGWQ than the Jinghe-Qinghe fault. The correlation between 4He, 20Ne, and N2 concentrations implies a common trapping mechanism for 4He, 20Ne, and N2 in hot spring gases. The 40Ar/36Ar ratios and N2/Ar ratios indicate that N2 and Ar are mostly meteoric, and YNWQ and HGWQ have more crustal-derived Ar contribution (40.56 and 51.49%, respectively). The δ13C(CO2)o values calculated by Rayleigh fractionation and CO2 concentration suggest that CO2 has inorganic and organic origins. The plot of Rc/Ra versus δ13C(CO2) indicates that the spring gas CO2 origin in the Sichuan–Yunnan block is mainly derived from mixing of limestone and organic sediments with minor mantle CO2. The δ13C(CH4) versus CH4/3He values indicate that the origin of methane is thermogenic and microbial oxidation. The low mantle-derived helium distribution pattern is most likely controlled by the weak fault activity rate, the small fault scale, and not obvious magmatic activity in the Sichuan–Yunnan block.

Earthquake hazard assessments for the Tokyo Region are complicated by the trench–trench triple junction where the oceanic Philippine Sea Plate not only underthrusts a continental plate but is also being subducted by the Pacific Plate. Great thrust earthquakes and associated tsunamis are historically recognized hazards from the Continental/Philippine Sea (Sagami Trough) and Continental/Pacific (Japan Trench) plate boundaries but not from the Philippine Sea/Pacific (Izu–Bonin Trench) boundary alone. Here we employed a series of historical and hypothetical rupture models to explain the widespread distribution of geological evidence for an unusually large tsunami found along 50 km of coastline east of Tokyo. Dating to about 1,000 years ago, this inferred tsunami predates local written history by several hundred years. We found that the inland extent of its sand sheet is best explained, in computer simulations, by displacement on one of the three plate boundaries offshore of the Boso Peninsula, which corresponds to the triple junction. The minimum magnitude scenario capable of generating the inland extent of inundation involves displacement along the Philippine Sea/Pacific boundary megathrust. This plate-boundary fault adds another potential source for earthquakes in the Tokyo Region and tsunamis in the Pacific Ocean. The Philippine Sea/Pacific boundary megathrust is another possible source of seismic hazard in the Tokyo Region and tsunamis in the Pacific, according to an assessment of 1,000 years of tsunami deposits along the Japanese coastline.

Carbon in the upper mantle controls incipient melting of carbonated peridotite and so acts as a critical driver of plate tectonics. The carbon-rich melts that form control the rate of volatile outflux from the Earth’s interior, contributing to climate evolution over geological times. However, attempts to constrain the carbon concentrations of the mantle source beneath oceanic islands and continental rifts is complicated by pre-eruptive volatile loss from magmas. Here, we compile literature data on magmatic gases, as a surface expression of the pre-eruptive volatile loss, from 12 oceanic island and continental rift volcanoes. We find that the levels of carbon enrichment in magmatic gases correlate with the trace element signatures of the corresponding volcanic rocks, implying a mantle source control. We use this global association to estimate that the mean carbon concentration in the upper mantle, down to 200 km depth, is approximately 350 ppm (range 117–669 ppm). We interpret carbon mantle heterogeneities to reflect variable extents of mantle metasomatism from carbonated silicate melts. Finally, we find that the extent of carbon enrichment in the upper mantle positively correlates with the depth at which melting starts. Our results imply a major role of carbon in driving melt formation in the upper mantle. The carbon concentration of Earth’s upper mantle increases with depth, indicating a role for carbon in melt formation, according to data on magmatic gases and volcanic rocks from ocean island and continental rift settings around the world.

The plate tectonic cycle produces chemically distinct mid-ocean ridge basalts and arc volcanics, with the latter enriched in elements such as Ba, Rb, Th, Sr and Pb and depleted in Nb owing to the water-rich flux from the subducted slab. Basalts from back-arc basins, with intermediate compositions, show that such a slab flux can be transported behind the volcanic front of the arc and incorporated into mantle flow. Hence it is puzzling why melts of subduction-modified mantle have rarely been recognized in mid-ocean ridge basalts. Here we report the first mid-ocean ridge basalt samples with distinct arc signatures, akin to back-arc basin basalts, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence in this region. This influence can also be identified in Atlantic and Indian mid-ocean ridge basalts but is nearly absent in Pacific mid-ocean ridge basalts. Such a hemispheric-scale upper mantle heterogeneity reflects subduction modification of the asthenospheric mantle which is incorporated into mantle flow, and whose geographical distribution is controlled dominantly by a “subduction shield” that has surrounded the Pacific Ocean for 180 Myr. Simple modeling suggests that a slab flux equivalent to ~13% of the output at arcs is incorporated into the convecting upper mantle., We discover a pervasive subduction influence in the Arctic, Atlantic and Indian mantle, which is nearly absent in the Pacific mantle. Such a hemispheric-scale upper mantle heterogeneity reflects the control of a “subduction shield” that has surrounded the Pacific Ocean for 180 Myr.

Geological records of subduction earthquakes, essential for seismic and tsunami hazard assessment, are difficult to obtain at transitional plate boundaries, because upper-plate fault earthquake deformation can mask the subduction zone signal. Here, we examine unusual shell layers within a paleolagoon at Lake Grassmere, at the transition zone between the Hikurangi subduction zone and the Marlborough fault system. Based on biostratigraphic and sedimentological analyses, we interpret the shell layers as tsunami deposits. These are dated at 2145–1837 and 1505–1283 yr B.P., and the most likely source of these tsunamis was ruptures of the southern Hikurangi subduction interface. Identification of these two large earthquakes brings the total record of southern Hikurangi subduction earthquakes to four in the past 2000 yr. For the first time, it is possible to obtain a geologically constrained recurrence interval for the southern Hikurangi subduction zone. We calculate a recurrence interval of 500 yr (335–655 yr, 95% confidence interval) and a coefficient of variation of 0.27 (0.0–0.47, 95% confidence interval). The probability of a large subduction earthquake on the southern Hikurangi subduction zone is 26% within the next 50 yr. We find no consistent temporal relationship between subduction earthquakes and large earthquakes on upper-plate faults.

Peridotite xenoliths entrained in magmas near the Alpine fault (New Zealand) provide the first direct evidence of deformation associated with the propagation of the Australian-Pacific plate boundary through the region at ca. 25–20 Ma. Two of 11 sampled xenolith localities contain fine-grained (40–150 μm) rocks, indicating that deformation in the upper mantle was focused in highly sheared zones. To constrain the nature and conditions of deformation, we combine a flow law with a model linking recrystallized fraction to strain. Temperatures calculated from this new approach (625–970 °C) indicate that the observed deformation occurred at depths of 25–50 km. Calculated shear strains were between 1 and 100, which, given known plate offset rates (10–20 mm/yr) and an estimated interval during which deformation likely occurred (

Constraining thickness and geothermal gradient of Archean continental crust are crucial to understanding geodynamic regimes of the early Earth. Archean crust-sourced tonalitic–trondhjemitic–granodioritic gneisses are ideal lithologies for reconstructing the thermal state of early continental crust. Integrating experimental results with petrochemical data from the Eastern Block of the North China Craton allows us to establish temporal–spatial variations in thickness, geothermal gradient and basal heat flow across the block, which we relate to cooling mantle potential temperature and resultant changing geodynamic regimes from vertical tectonics in the late Mesoarchean (~2.9 Ga) to plate tectonics with hot subduction in the early to late Neoarchean (~2.7–2.5 Ga). Here, we show the transition to a plate tectonic regime plays an important role in the rapid cooling of the mantle, and thickening and strengthening of the lithosphere, which in turn prompted stabilization of the cratonic lithosphere at the end of the Archean., Constraining the thermal state of the lithosphere is crucial to understanding geodynamic regime in early Earth. Here the authors reconstruct ~2.9–2.5 Ga thermal structure of continental lithosphere of the North China Craton using TTG and propose a systematic Archean geodynamic evolution process.

Paleogeography is the study of the changing surface of Earth through time. Driven by plate tectonics, the configuration of the continents and ocean basins has been in constant flux. Plate tectonics pushes the land surface upward or pulls it apart, causing its collapse. All the while, the unrelenting forces of climate and weather slowly reduce mountains to sand and mud and redistribute these sediments to the sea. This article reviews the changing paleogeography of the past 750 million years. It describes the broad patterns of Phanerozoic paleogeography as well as many of the specific paleogeographic events that have shaped the modern continents and ocean basins. The focus is on the changing latitudinal distribution of the continents, fluctuations in sea level, the opening and closing of oceanic seaways, mountain building, and how these paleogeographic changes have affected global climate, ocean circulation, and the evolution of life. This review presents an atlas of 114 paleogeographic maps that illustrate how Earth's surface has evolved during the past 750 million years. During that time interval, Earth has witnessed the formation and breakup of two supercontinents: Pannotia and Pangea. The continents have been transformed from low-lying flooded platforms to high-standing land areas crisscrossed by the scars of past continental collisions. Oceans have opened and closed, and then opened again in a seemingly never-ending cycle. ▪ The changing configuration of the continents and ocean basins during the past 750 million years is illustrated in 114 paleogeographic maps. ▪ These maps describe how the surface of Earth has been continually modified by mountain building and erosion. ▪ The changing paleogeography has affected global climate, ocean circulation, and the evolution of life. ▪ The data and methods used to produce the maps are described in detail.

The existence of mantle plumes was first proposed in the 1970s to explain intra-plate, hotspot volcanism, yet owing to difficulties in resolving mantle upwellings with geophysical images and discrepancies in interpretations of geochemical and geochronological data, the origin, dynamics and composition of plumes and their links to plate tectonics are still contested. In this Review, we discuss progress in seismic imaging, mantle flow modelling, plate tectonic reconstructions and geochemical analyses that have led to a more detailed understanding of mantle plumes. Observations suggest plumes could be both thermal and chemical in nature, can attain complex and broad shapes, and that more than 18 plumes might be rooted in regions of the lowermost mantle. The case for a deep mantle origin is strengthened by the geochemistry of hotspot volcanoes that provide evidence for entrainment of deeply recycled subducted components, primordial mantle domains and, potentially, materials from Earth’s core. Deep mantle plumes often appear deflected by large-scale mantle flow, resulting in hotspot motions required to resolve past tectonic plate motions. Future research requires improvements in resolution of seismic tomography to better visualize deep mantle plume structures at smaller than 100-km scales. Concerted multi-proxy geochemical and dating efforts are also needed to better resolve spatiotemporal and chemical evolutions of long-lived mantle plumes. Mantle plumes are an integral aspect of Earth’s convection system, yet, difficulty in imaging mantle upwellings led to controversies surrounding their origin, dynamics and composition. This Review synthesizes geophysical, geodynamic and geochemical constraints on mantle plumes and their importance in the Earth system.

Oceanic plates are growing through narrow boundaries, such as mid-ocean ridges and transform faults. However, the discovery of diffuse plate boundary suggests another type of plate boundary that accommodates difference in plate motion via internal deformation. Along the Central and Southeast Indian ridges, for example, the Capricorn and Macquarie microplates exhibit widespread diffuse boundaries and hence divide the Indo-Australian Plate further into the Indian, Australian, Capricorn, and Macquarie plates. As for microplates distributed along the East Pacific Rise and Pacific-Antarctic Ridge in the Pacific Ocean, however, the typical plate boundaries surrounding the given microplate are distinctly established. Global plate reorganization involving the changes in plate motion or in spreading direction can be accommodated by forming a microplate through ridge extinction, ridge propagation, and pseudofault formation. However, relations between these tectonic processes have not been quantitatively assessed. In particular, we aim to examine tectonic constrains on the formation processes of microplates with diffuse plate boundary. In this study, we compare plate size, plate age, full-spreading rates, thermal structures, total rotation, and rotation rate for the 9 microplates including extinct plates (i.e., Capricorn, Macquarie, and Mammerickx* microplates in the Indian and Southern Oceans; Galapagos, Easter, Juan Fernandez, Bauer*, Friday*, and Selkirk* microplates in the Pacific Ocean; extinct plates are denoted with asterisks). From this comparison, we find that the microplate formation would require certain tectonic conditions (e.g., full-spreading rates faster than 70–80 mm/yr and rotation rates faster than 5–6°/m.y.) to evolve into an independent and rigid plate with respect to the neighboring plates. If the conditions are not met, the same tectonic reorganization would result in a microplate with diffuse plate boundaries.

This study presents a procedure for compilation of earthquake catalog for southern Pakistan (spreading over Sindh and Balochistan provinces) and frontal offshore area of Arabian Sea. The active tectonic plate margins of Indian, Eurasian and Arabian Plates and their associated fault lineaments are dominant seismic sources in study area. These seismotectonic sources are extending beyond the terrestrial boundaries of southern Pakistan and diversified in their seismic potential, accumulation of stresses and earthquake generating mechanism. We have compiled earthquake datasets for pre-instrumental period (325 B.C. to 1900) and instrumental observations during January 1901 to August 2020. The seismological datasets are gathered from open source agencies including ISC, GCMT, USGS, PMD and published catalogs. Since earthquake magnitude has a crucial role in seismological studies, the catalog has been thoroughly processed for magnitude homogenization to Mw scale. We have developed magnitude conversion correlations for Mb and Ms to Mw by orthogonal and least square regression analyses. The comparison of these correlations with previously developed regression equations by other authors in similar environments helped us to determine the validity of derived correlations for the study area. The best correlated relations are used for converging multimagnitude types in compiled catalog to Mw scale. Further the catalog is processed for removal of foreshocks- and aftershocks by Reasenberg declustering algorithm. The declustered catalog is used for integrated analysis of various parameters such as completeness analysis in time and magnitude, histograms of depth and magnitude, estimation of GR parameters. It is observed that declustered catalog has completeness period (1960–2020) which is significant for appropriate seismicity analysis.

[The Late Triassic Chapeng thrust and the Dengzhangzi Basin system in the Yanshan Mountains of the North China Craton were an antiformal stack duplex with a frontal depression. , Abstract The configuration and kinematics of fold‐thrust belts are essential for clarifying the plate boundary conditions through which ancient orogenic belts evolved. Temporal and spatial variations in extension versus contraction within convergent plate margins are related to changes in plate kinematics and subduction geometry. The Yanshan Mountains, located along the northeastern margin of the North China Craton and bounded by the Central Asian Orogenic Belt to the north and the Pacific subduction zone to the east, underwent multiple phases of intra‐continental deformation during the Mesozoic. The issue of whether early Mesozoic deformation was extensional or contractional has remained controversial. New regional structural mapping and detailed sedimentological investigations, coupled with age constraints provided by zircon U‐Pb geochronology, provide sufficient temporal and spatial resolution to show that shortening and thrust‐top basin systems dominated during the early Mesozoic. Our results show that the Dengzhangzi Basin within the Lingyuan fold‐thrust belt developed during the construction of a major Late Triassic Chapeng antiformal‐stack duplex system, with episodic, east‐vergent forward‐breaking thrusts and subsequent ‘beheading’ by out‐of‐sequence, top‐to‐east thrusting in the latest Triassic or earliest Jurassic. The neighbouring Guojiadian Basin in the east was generated during top‐to‐SSE sinistral transpression along the Niuyingzi thrust system in the Middle to earliest Late Jurassic. These results support a new model of early craton decratonization involving (a) thrusting along the northern margin of the North China Craton and (b) transpressional deformation in the east driven by the Central Asian Ocean collision and flat‐slab subduction of the Palaeo‐Pacific Plate beneath the East Asian continental margin. Our findings suggest that large‐scale shortening and crustal/lithospheric thickening, triggered by flat‐slab subduction in the North China Craton, were fundamental components of craton decratonization. Subsequent slab roll‐back during the Cretaceous led to lithospheric thinning and crustal extension in the North China Craton.]

Research subject. The research covered the geological position, material composition and rock age of a comparatively small (about 32 km2) Bystrinskii gabbro massif. This massif underlies a tectonic plate package consisting of serpentinized dunits and harzburgites of the ophiolite association in the Eastern boundary of the Middle Urals. Methods. The content of petrogenic elements was measured by the Х-ray fluorescence method using an Х-ray multichannel spectrometer CPM-35. The analysis of rare-earth element contents was conducted using a NexION 300S mass-spectrometer. The composition of rock-forming minerals was studied using an Х-ray microanalyzer CamecaSX100. The age of the massif was determined by the 147Sm-143Nd method of isotope dating. Amphibole geobaometers were used to determine the depth of the rock formation. Results. According to the petro- and geochemical features and composition of the rock-forming minerals, the 147Sm-143Nd isotope age of the rocks was found to be 587 Ma. It was shown that gabbroids in the massif are represented by two petrographic varieties. The predominant type of the rocks is gabbrodolerites, which are similar to the isotropic gabbros of undisturbed ophiolite sections in terms of mineral composition, structure, geochemical features and the depth of formation (not more than 2–3 km). The mapping results showed the massif under study to be the largest among those described thus far. The medium grained gabbroids, which are present in lesser quantities, differ sharply from gabbrodolerites in terms of lower contents of Fe, Ti, both rockforming (K, Na) and rare (Li, Rb, Cs) alkalis, Ba, V, Y, Nb, Zr, Hf and elements of rare-earth group, as well as by significantly higher quantities of Ca, Mg and Cr. The depth of their formation is 10–12 km, which corresponds to the upper mantle. Conclusions. The obtained information demonstrates that fragments of two levels of the ophiolite section are tectonically aligned in the Bystrinskii massif: relatively shallow isotropic gabbros of the upper part of the ophiolite section and deep gabbros of the mantle part of the ophiolite section.

Convergence of the Indian Plate towards Eurasia has led to the building of the Himalaya, the highest mountain range on Earth. Active mountain building involves a complex interplay between permanent tectonic processes and transient seismic events, which remain poorly understood. In this Review, we examine the feedbacks between long-term tectonic deformation (over millions of years) and the seismic cycle (years to centuries) in the Himalaya. We discuss how surface morphology of the Himalaya indicates that the convergence is largely accommodated by slip on the Main Himalayan Thrust plate boundary fault, which developed in the roots of the mountain range over millions of years. At shorter (decadal) timescales, tectonic geodesy reveals that elastic strain is periodically released via earthquakes. We use examples from earthquake cycle models to suggest that partial ruptures could primarily occur in the downdip region of the Main Himalayan Thrust. Great (Mw 8+) Himalayan earthquakes are more commonly associated with complete megathrust ruptures, which release accumulated residual strain. By synthesizing numerous observations that co-vary along strike, we highlight that tectonic structures that developed over millions of years can influence stress accumulation, structural segmentation, earthquake rupture extent and location, and, consequently, the growth of the mountain range. Mountain building involves complex and debated feedback cycles between both permanent tectonic and transient seismic processes. This Review discusses how the fault architecture and tectonic segmentation of the Himalaya influence the seismic cycle, which in turn impacts the long-term growth of the mountain range.

Earthquakes are a consequence of the motions of the planet’s tectonic plates, yet predicting when and where they may occur, and how to prepare remain some of the shortcomings of using scientific knowledge to protect human life. A devastating Mw 7.0 earthquake on October 30, 2020, offshore Samos Island, Greece was a consequence of the Aegean and Anatolian upper crust being pulled apart by north–south extensional stresses resulting from slab rollback, where the African plate is subducting northwards beneath Eurasia, while the slab is sinking by gravitational forces, causing it to retreat southwards. Since the retreating African slab is coupled with the overriding plate, it tears the upper plate apart as it retreats, breaking it into numerous small plates with frequent earthquakes along their boundaries. Historical earthquake swarms and deformation of the upper plate in the Aegean have been associated with massive volcanism and cataclysmic devastation, such as the Mw 7.7 Amorgos earthquake in July 1956 between the islands of Naxos and Santorini (Thera). Even more notable was the eruption of Santorini 3650 years ago, which contributed to the fall of the Minoan civilization. The Samos earthquake highlights the long historical lack of appreciation of links between deep tectonic processes and upper crustal deformation and geological hazards, and is a harbinger of future earthquakes and volcanic eruptions, establishing a basis for studies to institute better protection of infrastructure and upper plate cultures in the region.

Reconstructions of past seafloor age make it possible to quantify how plate tectonic forces, surface heat flow, ocean basin volume and global sea-level have varied through geological time. However, past ocean basins that have now been subducted cannot be uniquely reconstructed, and a significant challenge is how to explore a wide range of possible reconstructions. Here, we investigate possible distributions of seafloor ages from the late Palaeozoic to present using published full-plate reconstructions and a new, efficient seafloor age reconstruction workflow, all developed using the open-source software GPlates. We test alternative reconstruction models and examine the influence of assumed spreading rates within the Panthalassa Ocean on the reconstructed history of mean seafloor age, oceanic heat flow, and the contribution of ocean basin volume to global sea-level. The reconstructions suggest variations in mean seafloor age of ∼15 Myr during the late Palaeozoic, similar to the amplitude of variations previously proposed for the Cretaceous to present. Our reconstructed oceanic age-area distributions are broadly compatible with a scenario in which the long-period fluctuations in global sea-level since the late Palaeozoic are largely driven by changes in mean sea-floor age. Previous suggestions of a constant rate of seafloor production through time can be modeled using our workflow, but require that oceanic plates in the Palaeozoic move slower than continents based on current reconstructions of continental motion, which is difficult to reconcile with geodynamic studies.

From southern Sao Francisco Craton (Brazil), the Itaguara retroeclogite with so little amphibole (~20%) and plagioclase (~1%) should not be considered a garnet amphibolite (as claimed by Cutts 2020) according to IUGS/Subcommission on the Systematics of Metamorphic Rocks. The ten main assertions of Cutts (2020) are individually replied in this Discussion manuscript. The new discovery of ~2.2 Ga E-MORB signature retroeclogite in the Itaguara Sequence (Chaves and Porcher 2020), close to ~2.1 Ga peraluminous (S-type) syn-collisional Corrego do Peixoto granite generated by partial melting of the mica-quartz schist from the Itaguara accretionary prism (Chaves et al. 2019; Chaves and Coelho 2020), correspond to one of the earliest records of subduction accretion then continental collision in the world.

The Fairweather fault (southeastern Alaska, USA) is Earth’s fastest-slipping intracontinental strike-slip fault, but its long-term role in localizing Yakutat–(Pacific–)North America plate motion is poorly constrained. This plate boundary fault transitions northward from pure strike slip to transpression where it comes onshore and undergoes a 6–8 km/m.y. exhumation rates that increases in age away from the bend. We interpret this migration of rapid, transient exhumation to reflect prolonged advection of the Cenozoic–Cretaceous sedimentary cover of the eastern Yakutat microplate through a stationary restraining bend along the edge of the North America plate. Yakutat cooling ages imply a long-term strike-slip rate (54 ± 6 km/m.y.) that mimics the millennial (53 ± 5 m/k.y.) and decadal (46 mm/yr) rates. Fairweather fault slip can account for all Pacific–North America relative plate motion throughout Quaternary time and indicates stability of highly localized plate boundary strike slip on a single fault where extreme rock uplift rates are persistently localized within a restraining bend.

[Schematic illuration of tectonic deformations in the Porcupine Basin. , Abstract The Porcupine Basin is a large underexplored sedimentary basin located offshore west of Ireland within the structurally complex European North Atlantic Margin. The basin has evolved through multiple Jurassic–Recent phases of deformation and although the overall plate tectonic context of the margin is well‐documented, there are still uncertainties regarding the phases of tectonic activity, and their associated strain distribution and fault kinematics. Based on the analysis of large volumes of 2D and 3D seismic data from the Porcupine Basin, we provide an overview of the nature and origin of multiple fault systems, both tectonic and nontectonic, with links to regional tectonic events where possible. Three distinct basin‐wide phases of tectonically induced extensional faulting are recognized: (a) Late Jurassic N‐S to NE‐SW trending rift faults, (b) Late Cretaceous E‐W to ENE‐WSW trending normal faults and (c) Mid Eocene N‐S trending faults. The Jurassic faults were active over a period of 11.5 Myr between the Oxfordian and Kimmeridgian but with an intervening 4.5 Myr period of quiescence providing a two‐stage rift evolution. The Late Cretaceous faulting in the Porcupine Basin broadly correlates with extension in the Celtic Sea basins and is tentatively attributed to the rotational spreading of the Bay of Biscay in the south. The Mid Eocene phase of extension, which coincides with the onset of spreading between Europe and Greenland (Atlantic spreading), resulted in partial reactivation of the Jurassic faults. A series of non‐tectonic fault systems occur within specific stratigraphic intervals suggesting a compactional or gravitationally driven origin, including basinward dipping normal faults within a Palaeocene–early Eocene deltaic sequence, and multiple tiers of polygonal faults within Cretaceous, late Eocene and Neogene strata.]

Although central to an understanding of Earth's paleogeography and the myriad processes that it affects, the geometry of Pangea during the early phase of its lifetime has remained a topic of contention since the plate tectonic revolution. Despite decades of analysis and discussion, the crux of this debate still largely hinges on sparse, legacy paleomagnetic data derived from early Permian rocks of the Moroccan Meseta. In this work, we present the results of a study designed to revisit, update and expand on those key data, with the provision of new geochronologic and paleomagnetic results from six Permo-Carboniferous basins in central Morocco. New U-Pb zircon ages from volcanic rocks substantiate and refine existing geochronological data and reveal that volcanism among the studied basins spanned approximately 30 Ma, from at least 305 to 277 Ma, but was possibly punctuated by a more intense pulse in the mid-early Permian (~285 Ma). These new U-Pb data furthermore suggest that the age estimates previously assigned to the key poles from the Moroccan Meseta are probably too young, by some ~10 Ma. New paleomagnetic results from six basins yielded a common, well-defined remanent magnetization from 20 sites that is demonstrated to be pre-middle Permian in age. However, it remains unclear whether this magnetization (which is directionally similar to the previous paleomagnetic data from the same basins) is a primary magnetization acquired at ~285 Ma, or a syn-folding remagnetization that was acquired shortly thereafter, at ~275 Ma. In adopting both interpretations as alternative hypotheses, we examine the corresponding paleogeographic implications of both. Through exhaustive comparisons with reference apparent polar wander paths and the direct reconstruction of Gondwana using these new paleomagnetic results, we demonstrate that in either case (i.e. whether the remanent magnetization is primary or was acquired soon after during folding) the data is compatible with a Pangea A geometry during the early Permian. We close with a topical discussion of some persisting arguments used to defend Pangea B and why we consider them to be flawed.

The discovery of Dickinsonia in India allows assessment of biogeographic provinces and plate tectonic reconstructions for the late Ediacaran. The fossils were found in the roof of Auditorium Cave at Bhimbetka Rock Shelters, a UNESCO World Heritage Site for Paleolithic and Mesolithic cave art, near Bhopal, Madhya Pradesh. The fossils are identical with Dickinsonia tenuis from the Ediacara Member of the Rawnsley Quartzite in South Australia, and like them also show deformation due to lateral impingement, arcuate pieces missing, and alignment. They are within the late Ediacaran, Maihar Sandstone of the Bhander Group, in red sandstones formed in coastal plain paleoenvironments, including eolian, tsunamite, and intertidal bedforms. This new occurrence confirms assembly of Gondwanaland by 550 Ma, but not reconstructions adjusted for true polar wander. Cloudina and other small shelly marine fossils were low latitude, but vendobionts such as Dickinsonia were at temperate to subtropical latitudes.

The study interprets the effect of seasonal (pre-, co- and post-monsoon) hydrological loading due to the Ganga river basin over the seismicity and geodetic deformation in the Garhwal Himalayan region. Geodetic data from six cGPS sites are used, three sites out of six are established in the Himalayan region, one is located in the Ganga basin and two sites are located in the Indian shield. First, we estimated the average seasonal variation in GRACE-derived TWS of entire India for the period of 2002–2016. It is observed the seasonal effect over TWS (Terrestrial Water Storage) due to hydrological fluctuations in the Indo-Gangetic Plain (IGP). It has also been noticed that the geodetic velocities for both the North and East components are more in pre-monsoon than post-monsoonal season. Whereas the vertical component in cGPS sites of Himalaya (DEHR and MAND) agrees to the hypothesis of upliftment during post-monsoon and subsidence in pre-monsoon. TWS mass change is detected high during the co-monsoon (2.32 × 104 km3) and it is observed low −2.22 × 104 km3 (in pre-) and −8.13 × 103 km3 (in post-) monsoon seasons respectively. GPS measured horizontal displacement agrees with seasonal loading but it contains some anomalous behaviour, which may be the result of surface hydrological mass movement or the effect of the Gorkha earthquake, 2015, however an inverse relation between vertical geodetic displacement and loading have been observed. The average strain rate values over cGPS sites during 2016–2018, are more negative in post-monsoon than in pre-monsoon which means that plate movement is highly compressional. We have also inferred a significant role of loading over the seismicity and linear strain rate, which increases with decreasing hydrological loading in the Ganga river basin and vice versa.

The North Pacific subtropical gyre (NPSG) plays a major role in present global ocean circulation. At times, the gyre has coursed through the South China Sea, but its role in the evolutionary development of that Sea remains uncertain. This work systematically describes a major shift in NPSG paleo-circulation evident from sedimentary features observed in seismic and bathymetric data. These data outline two contourite depositional systems—a buried one formed in the late Miocene, and a latest Miocene to present-day system. The two are divided by a prominent regional discontinuity that represents a major shift in paleo-circulation during the latest Miocene (~ 6.5 Ma). The shift coincides with the further restriction of the South China Sea with respect to the North Pacific due to the formation of the Luzon Strait as a consequence of further northwest movement of the Philippine Sea plate. Before that restriction, data indicate vigorous NPSG circulation in the South China Sea. Semi-closure, however, established a new oceanographic circulation regime in the latest Miocene. This work demonstrates the significant role of recent plate tectonics, gateway development, and marginal seas in the establishment of modern global ocean circulation.

The distribution of permanent deformation near strike-slip plate boundaries and the underlying controlling variables are commonly poorly understood. Here we examine the crustal deformation across the northern Dead Sea fault system based on paleomagnetic observations and mechanical modeling. We focus our investigation on the region of the Lebanese restraining bend where the fault system strikes obliquely to the general Sinai-Arabia plate motion. We construct a series of crustal elasto-plastic models in which kinematics is based on geodetic measurements, and the geometry of the plate boundary is constrained by gravity data. Both the observed regional vertical axis rotations and the model results display significant counterclockwise rotations (as much as ∼50°) confined to the northern Sinai microplate located west of the bend. On the other hand, relatively minor rotations (

The Haiti region – bounded by two strike-slip faults expressed both onshore and offshore – offers a unique opportunity for an amphibious drilling project. The east–west (EW)-striking, left lateral strike-slip Oriente–Septentrional fault zone and Enriquillo–Plantain Garden fault zone bounding Haiti have similar slip rates and also define the northern and southern boundaries of the Gonâve Microplate. However, it remains unclear how these fault systems terminate at the eastern boundary of that microplate. From a plate tectonic perspective, the Enriquillo–Plantain Garden fault zone can be expected to act as an inactive fracture zone bounding the Cayman spreading system, but, surprisingly, this fault has been quite active during the last 500 years. Overall, little is understood in terms of past and present seismic and tsunami hazards along the Oriente–Septentrional fault zone and Enriquillo–Plantain Garden fault zone, their relative ages, maturity, lithology, and evolution – not even the origin of fluids escaping through the crust is known. Given these unknowns, the Haiti-Drill workshop was held in May 2019 to further develop an amphibious drilling project in the Haiti region on the basis of preproposals submitted in 2015 and their reviews. The workshop aimed to complete the following four tasks: (1) identify significant research questions; (2) discuss potential drilling scenarios and sites; (3) identify data, analyses, additional experts, and surveys needed; and (4) produce timelines for developing a full proposal. Two key scientific goals have been set, namely to understand the nature of young fault zones and the evolution of transpressional boundaries. Given these goals, drilling targets were then rationalized, creating a focus point for research and/or survey needs prior to drilling. Our most recent efforts are to find collaborators, analyze existing data, and to obtain sources of funding for the survey work that is needed.