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[Display omitted] • The Early Cretaceous marine transgressive cycle in NE China resulted from the subduction of the Paleo-Pacific Plate. • The Cretaceous Jixi Basin suffered initial back-arc extension, regional back-arc extension and block-continent collision. • Study on basin tectonics and geochronology could clarify conflicts of endemic transgressions and global sea-level changes. The occurrence of abundant marine fossils from non-marine basins in NE China indicated a distinctive Early Cretaceous phase of marine transgressions along the NW Pacific margin. Such a transgression has not only profoundly shaped the regional climate and terrestrial ecosystem, exerting a critical influence on rise-radiation-extinction of the world-famous terrestrial Jehol Biota, but also significantly facilitated the accumulations of hydrocarbon source rocks in NE China. In light of a joint study on marine and non-marine fossils and newly reported high-precision geochronological data, the timing of the transgression had been constrained as the late Early Cretaceous, puzzlingly disagreeing with coeval global sea-level changes. Employing seismic reflections, drill-holes and well-exposed outcrops, this study achieves structural architecture and kinematics of the Jixi basin (in eastern Heilongjiang), west of the Paleo-Pacific subduction accretionary prisms, and firstly affords subduction-related tectonic origins for the transgressive cycle. Based on tectonic events constrained by this study, transgressive initiation (Barremian to early Aptian Didao Formation), climax (middle Aptian to early Albian Chengzihe Formation) and termination (latest Albian to Cenomanian Houshigou Formation) correlate with initial back-arc extension, regional back-arc extension and block-continent collision linked to the subduction of the Paleo-Pacific Plate, respectively. Utilizing the delicate anatomy of tectonic responses to subduction and block accretion tectonics along the NW Pacific margin, we throw light on enigmatic dynamics for the transgressive cycle, offering new insights into the conflicts of endemic transgressions and global sea-level changes. [ABSTRACT FROM AUTHOR]

Previous studies have proposed that the Eastern Tibetan Plateau underwent ∼E–W oblique crustal shortening, due to the eastward extrusion of the plateau since ∼5–2 Ma to present. However, the effects of the oblique thrusting on the three-dimensional (3D) fold morphology and kinematics in the front of the Longmen Shan fold-and-thrust belt are still poorly understood. We use 3D seismic data to produce five 3D geometric models and compare our results with structural models of the Yanjinggou anticline in the Longmen Shan fold-and-thrust belt, to investigate the effects of oblique thrusting on 3D fold evolution. The results show that regional oblique thrusting occurred within the LMS fold-and-thrust belt, resulting in rotation and a curved structural morphology, and suggest that this process may be applicable globally to both small- and regional-scale structures, as well as larger-scale orogenic belts in obliquely convergent settings. • The effects of oblique thrusting on 3D fold geometry and kinematics are investigated. • The Yanjinggou anticline developed as a trishear fault-propagation fold with 1.2 km shortening. • The Yanjinggou anticline was affected by oblique thrusting at an angle of 55°. Three-dimensional (3D) subsurface seismic data acquisition and modeling are rarely undertaken; consequently, the complex effects of oblique thrusting on the 3D morphology and kinematics of folds are still poorly understood. We use 3D seismic data to produce five 3D geometric models and compare our results with structural models of the Yanjinggou anticline in the Longmen Shan fold-and-thrust belt, to investigate the effects of oblique thrusting on 3D fold evolution. 3D geometric modeling results reveal that oblique thrusting may cause fold asymmetry, vertical axis rotation, and a curved fold axis. 3D seismic interpretations and structural modeling suggest that the Yanjinggou anticline developed as a trishear fault-propagation fold and experienced a maximum shortening amount of 1.2 ± 0.1 km. The 3D structural and geometric models are consistent with paleomagnetic results, suggesting that the anticline was affected by oblique thrusting at an angle of 55° above a listric thrust fault with three fault ramps (19°, 30°, and 40°), causing the fold to rotate and develop a curved morphology. The integrated method used in this study to investigate the effects of oblique thrusting on 3D fold morphology and kinematics can be applied to regional oblique thrusting in the Longmen Shan and other fold-and-thrust belts worldwide. [ABSTRACT FROM AUTHOR]

On January 21st, 2016, a Ms 6.4 earthquake hit Menyuan County, Qinghai province, China. The nearest known fault is the Leng Long Ling (LLL) fault which is located approximately 7 km north of the epicenter. This fault has mainly shown sinistral strike-slip movement since the late Quaternary Period. However, the focal mechanism indicates that it is a thrust earthquake, which is different from the well-known strike-slip feature of the LLL fault. In this study, we determined the focal mechanism and primary nodal plane through multi-step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the China Digital Seismic Network (CDSN). Our results show that the rupture duration was short, within 0–2 s after the earthquake, and the rupture expanded upwards along the fault plane. Based on these fault parameters, we then solve for variable slip distribution on the fault plane using the InSAR data. We applied a three-segment fault model to simulate the arc-shaped structure of the northern LLL fault, and obtained a detailed slip distribution on the fault plane. The inversion results show that the maximum slip is 0.43 m, and the average slip angle is 78.8°, with a magnitude of Mw 6.0 and a focal depth of 9.38 km. With the geological structure and the inversion results taken into consideration, it can be suggested that this earthquake was caused by the arc-shaped secondary fault located at the north side of the LLL fault. The secondary fault, together with the LLL fault, forms a normal flower structure. The main LLL fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block. Therefore, we infer that this earthquake is the manifestation of a neotectonics movement, in which the bulging fault block is lifted further up under the compresso-shear action caused by the Tibetan Plateau pushing towards the northwest direction. [ABSTRACT FROM AUTHOR]

The Yilan-Yitong Fault Zone (YYFZ), which is composed of two nearly parallel branches with a spacing of 5–30 km and a length of ∼1100 km, is considered to be the key branch of the Tancheng-Lujiang Fault Zone (TLFZ) in NE China. It was traditionally believed that the YYFZ experienced weak activity or was inactive during the Late Quaternary, without the capability to generate strong earthquakes (M ≥ 7), based on the absence of typical outcrops and large historical or instrumental earthquakes (M > 6). However, our paleoseismic study shows that the YYFZ is the primary seismotectonic structure (M ≥ 7) that poses significant earthquake threats to NE China. The synthesis of data collected from geologic investigations, geomorphic mapping, trench logging and the dating of samples indicates that the YYFZ is an active structure that has undergone segmented strong tectonic deformation since the Late Quaternary with a characteristic assemblage of landforms, including linear scarps and troughs, offset or deflected streams, linear sag ponds, small horsts and grabens. The latest ruptures of the YYFZ migrated from previous boundary faults into the basin interior, forming a left-stepping en echelon pattern in plain view, and the kinematics of these events in the Late Quaternary were dominated by reverse dextral slipping. Multi-segment cluster faulting might have occurred during three cluster periods, i.e., ∼34750–35812 a BP, ∼21700–22640 a BP, and ∼4000 a BP-present, which implies that the recurrence interval of large earthquakes along the YYFZ may be as long as tens of thousands of years. [ABSTRACT FROM AUTHOR]

The North China Plate (NCP) underwent multi-phase intracontinental deformation during the Mesozoic, which is a much-debated research subject. Here we present a case study of this deformation inferred from regional-scale Helanshan superposed folds in the west of the NCP. New structural analyses and fault kinematic analyses in the Helanshan Structural Belt (HSB) indicate a two-stage syn-folding paleo-stress field, comprising early NNE–SSW compression, with mean orientations 190°/01° (plunge direction/plunge) for σ 1 , 283°/26° for σ 2 , and 100°/63° for σ 3 , and later WNW–ESE compression with mean orientations of σ 1 , σ 2 , and σ 3 at 124°/07°, 213°/04°, and 001°/75°, respectively. These results, combined with geochronological analysis, indicate two episodes of shortening in this belt during the Mesozoic. Late Triassic–Early Jurassic NNE–SSW shortening, which produced ∼8.1 km of horizontal shortening, led to the development of open WNW-trending fold structures. Subsequent Late Jurassic–Early Cretaceous WNW–ESE shortening, which produced ∼18.7 km of horizontal shortening, reshaped the early WNW-trending structures and generated close, overprinting NNE-trending folds that resulted in the development of the regional-scale superposed folds in this area. In terms of geodynamics, the early NNE–SSW shortening is likely to be related to Indosinian intercontinental convergence between the North China Plate and the Yangtze Plate, and the later WNW–ESE shortening is likely to have been related to subduction of the Paleo-Pacific Plate. The regional structural analysis indicates that the whole of the western North China Plate experienced two-phase contractional deformation during the Mesozoic, as manifest by the early NNE–SSW and the late WNW–ESE shortening that characterized Mesozoic intracontinental deformation in the western NCP. [ABSTRACT FROM AUTHOR]

The Shanxi Rift, an intracontinental belt along the eastern margin of the Ordos Block, North China Plate, has undergone multi-stage extensional deformation during the late Cenozoic. In this study, new fault kinematic analysis of boundary faults in the Shanxi Rift, constrained by geochronological data, defines a three-stage tectonic stress regime since the late Miocene, providing new structural evidence for deciphering the northeastward growth of the Tibetan Plateau. The earliest stage involved a transtensional stress regime of NW–SE extension and NE–SW compression in the late Miocene–early Pleistocene (ca. 10–1.8 Ma) and characterized by mean principal stress axes of σ 1 at 344.7°/87.2°, σ 2 at 217.6°/01.1°, and σ 3 at 128.1°/01.0°. The early transtensional stress regime was responsible for the opening of the Shanxi Rift and was very likely associated with intensive right-lateral pull-apart activity in the eastern Ordos Block due to the northeastward growth of the Tibetan Plateau. During the second stage, the stress regime changed to less intense NE–SW extension, with mean stress orientations of 323.3°/85.2° for σ 1 , 127.5°/02.9° for σ 2 , and 214.9°/02.6° for σ 3 in the early late Pleistocene (ca. 1.8–0.11 Ma). This stage is marked by a distinct shift from fluvio-lacustrine to fluvio-piedmont sedimentary facies at the end of the early Pleistocene, and the widespread eruption of basalt in the Datong Basin north of the Shanxi Rift. This short-lived extension appears to be the result of relaxation in the midst of crustal shortening during growth of the Tibetan Plateau. The third stage was transtensional, characterized by NNW–SSE extension and WNW–ESE compression ( σ 1 at 060°/88.9°, σ 2 at 074.9°/03.9°, and σ 3 at 164°/00°) since the late Pleistocene (ca. 0.11 Ma), causing dextral shear deformation in the Shanxi Rift and the disappearance of its paleo-lake. This stage resulted from regional ENE–WSW shortening due to northeastward growth of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The main brittle faults in the Jiangsu part of the Tan-Lu Fault Zone, East China, are, from east to west, faults F 1 , F 5 , F 2 , F 3 , and F 4 . The details of their Quaternary activity remain controversial. We present structural, depositional, topographical, and geochronological evidence that indicates widespread fault activity during the Quaternary. Our fieldwork revealed that faults F 1 , F 5 , F 2 , and F 3 cut Quaternary sediments. Each fault produces a narrow gouge belt in the Quaternary sediments and incohesive fault rocks consisting of gouge, unconsolidated breccia and cataclastic belts in the bedrock. With the exception of dextral faulting along the northern part of the fault F 1 , the main Quaternary faults show evidence of thrusting with a minor dextral component. Analysis of a large amount of fault-slip data demonstrates that ENE–WSW compression was responsible for the Quaternary faulting. Our OSL dating results, combined with observed changes in Quaternary sediment thicknesses, indicate that except for Holocene activity on the northern part of fault F 1 , and probable Quaternary activity on the northern part of fault F 4 , the most recent period of activity on the main faults in the Jiangsu part of the Tan-Lu Fault Zone was the late Pleistocene. These inferences are consistent with the absence of M ⩾ 4.0 earthquakes along the fault zone. Fault displacement data and Quaternary sedimentation suggest that Quaternary activity was more intense in the late Pleistocene, and that faults F 2 and F 5 were the most intensely active. Our field investigation shows that faults F 1 –F 4 originated from the reactivation of Cretaceous graben-boundary faults whereas fault F 5, with its varied dip directions, was derived from the reactivation of antithetic normal faults associated with the boundary faults in the eastern graben. [ABSTRACT FROM AUTHOR]

The middle segment of the NNE–SSW-striking Tan-Lu Fault Zone (TLFZ) crosses the Bohai Bay in East China. This fault zone is a large seismically active belt that was responsible for the 1969 M (magnitude) 7.4 Bohai earthquake. However, the geometry, kinematics, and detailed characteristics of the most recent Quaternary seismic activity along the TLFZ in the Bohai Bay area are debated, primarily as the fault crops out below sea level in this area. Here, we present the results of a series of seismic profiles that enable the identification of Quaternary activity along the TLFZ within the Bohai Bay area. These data indicate that the Quaternary TLFZ crops out over a wide area of the Bohai Bay and is dominated by two main faults, both of which dip steeply to the west. Each of these two main faults consists of several left-stepping en-echelon faults. Quaternary activity along the TLFZ was generally focused along pre-existing Paleogene–Neogene faults. The seismic profiles, combined with the distribution of earthquakes in this area, demonstrate that the TLFZ in the southern and central areas of the Bohai Bay was last active during the Holocene, whereas the last movements along the faults in the northern Bohai Bay area range from late Pleistocene in the south to early–middle Pleistocene and the end of the Neogene in the north. The seismic profiles show both normal and reverse offset of the base of the Quaternary sediments by the Tan-Lu faults, although the normal offset predominates. Anticlines developed in Quaternary sediments occur close to the Quaternary Tan-Lu faults, and the TLFZ is also associated with an angular unconformity between Holocene and Pleistocene sediments. It is likely that the TLFZ was dominated by reverse dextral slip during the Holocene, whereas all of the Quaternary faulting before this involved alternating reverse and normal dextral slip. Oblique extension is most likely responsible for the normal dextral slip along the TLFZ, whereas focal mechanisms, GPS (global positioning system) data, and in situ stress measurements all suggest that ENE–WSW compression led to the reverse dextral faulting associated with numerous recent earthquakes in the Bohai Bay area. [ABSTRACT FROM AUTHOR]

• The WNW-trending dextral transpression occurred at ~250–225 Ma in South China. • NE-trending sinistral transpression was developed in the late Triassic in the SCB interior. • A Triassic two-stage intra-continental orogenesis is proposed in the South China Block. • It was derived by Paleotethyan scissor-like closure and its adjacent interactions. The South China Block (SCB) is tectonically bounded by the Tethyan and Pacific subduction zones and the Qinling-Dabie HP-UHP metamorphic zone. Triassic tectonic activity was a key phase in the tectonic history of the SCB and in creating the fundamental framework of East Asia. The geometry and kinematics of the Triassic deformation sheds light on the mechanism driving intra-continental orogenesis in the SCB. Our new field- and mapped- based structural analysis, along with thermo-chronological dating results, reveal two-stage distinct Triassic deformations in the southern SCB involving top-to-north dextral thrusting at ~250–225 Ma and NE-trending sinistral transpression at ~230–190 Ma. Early Triassic dextral transpression is marked by WNW-trending high-strain zones and thrust nappes/sheets, which might have been rooted beneath the Hainan-Yunkai basement along a low angle, middle-upper crustal basal detachment. It transformed from a thick-skinned fold-and-thrust belt to thin-skinned Jura-like patterns with northerly-propagating deformation. Late Triassic NE-trending sinistral transpression was accompanied by a series of the parallel folds and thrusts in the SCB interior, resulting in the development of the regional positive-flower geometry and reactivation of the pre-existing structures. Such signatures, in combination with the available geological, geochronological, and paleogeographic observations, suggest two-stage (early-middle and late Triassic) intra-continental orogenesis in the SCB, were controlled by the clockwise scissor-like closure of the Paleotethyan Ocean and its interactions with the adjoining blocks including deep-subduction beneath the North China Block and limited lateral extrusion due to the obstructing paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

• Two stages of folds are identified on the northern margin of the North China Craton. • The D 1 folds were crossly superimposed by the D 2 folds and both formed in Paleozoic. • A dynamic transition occurred in middle Paleozoic in the northernNorth China Craton. Accretionary kinematic history of the Central Asia Orogenic Belt (CAOB) remains unclear in previous geological studies. Based on detailed structural analysis of newly identified folds on the northern margin of the North China Craton (NCC), we propose a tectonic model suggesting that Paleozoic accretion of the orogenic belt includes two phases of deformation. The first phase of deformation is oblique collision of the Bainaimiao Arc and the NCC, which was followed by orthogonal subduction of the Paleo-Asian Ocean in the second phase of deformation. The change of plate kinematics is supported by two generations of folding, namely D 1 (D B) and D 2 (D A). Both D 1 (D B) and D 2 (D A) folds developed in the Bayan Obo Group (BOG), a Meso- and Neoproterozoic rift sequence deposited on the passive continental margin of the NCC. D 1 (D B) folds were superimposed by the east-west trending D 2 (D A) folds. The D 1 (D B) folds developed as a result of oblique collision of the Bainaimiao arc and the NCC. The D 2 (D A) folds developed in response to the southward orthogonal subduction of the Paleo-Asian Ocean Plate. They formed between latest Silurian and Early Permian, coeval with the two accretion events at the northern edge of the NCC. Our study suggests that multiphase deformation of sedimentary layers on the subducting plates provide important constraints for kinematic evolution of plate tectonics. [ABSTRACT FROM AUTHOR]

The basin-bounding fault system along the southeastern margin of the Ordos Block records three stages of extensional deformation during the Quaternary. This Quaternary deformation in the uppermost crust is possibly related to crust-mantle decoupling. • Three stages of extensional deformation were established during the Quaternary. • Transformation of kinematics resulted in transition of geomorphic pattern. • Quaternary extensional deformation resulted from the crust-mantle decoupling. The southeastern margin of the Ordos Block (SEMOB) is located at the juncture of the North China Block, the Ordos Block, and the Qinling Orogen. A series of faulted basins has developed in this area since the Cenozoic. The latest focal mechanism solution and stress field analyses indicate that the SEMOB is located at the adjacent regions of present different stress field, although the structural activity and internal mechanisms of this changing remain unclear. In this paper we describe the results of a study into the fault systems and Quaternary deformation between the Linfen and Weihe basins on the SEMOB. Based on the deformation sequences, kinematic analyses and activity timing, we found that the strain field in SEMOB underwent three evolutionary stages during the Quaternary: NW–SE extension in the early Pleistocene, NE–SW extension in the middle Pleistocene, and ca. N–S oblique extension from the late Pleistocene to the Holocene. This evolution of the strain field affected both the geomorphic patterns and the activity of paleo-earthquake events along the SEMOB during the Quaternary. Quaternary extensional deformation in the upper crust along the SEMOB possibly resulted from crust-mantle decoupling, which may be related to eastward expansion of the Tibetan Plateau and subduction of the Pacific and Philippine Sea plates. [ABSTRACT FROM AUTHOR]

• Field observations demonstrate the geometry and kinematics of Seertengshan Piedmont Fault. • Both planar and curved normal faults characterize the outcropping fault zones. • Sequential development of normal faults resulted in rotation of fault blocks. • Similarity of geometry and kinematic behaviors exists at multiple spatial scales. Although rotation of fault blocks during seismic and long-term periods has long been recognized in extensional tectonic regimes, the geometry and kinematic behaviors of normal faults at outcrop scale have scarcely been investigated in sufficient detail. In this study, combining with the analysis of high-resolution topography acquired by small unmanned aerial vehicle (sUAV) using the structure-from-motion (SfM) technique, we present the results of our field observations on the structural characteristics of the Seertengshan Piedmont Fault (SPF), a major active normal fault bounding the northern margin of the Hetao Graben, North China. Although previous studies have reported the recent tectonic activity of this fault including timing of most recent earthquake, average slip rate and repeat time of paleo-earthquakes, few of them have focused on geometric patterns of the outcropping fault zones, which provide excellent outcrop-scale examples to investigating geometry and kinematics of active normal faults. Besides the observed prominent fault scarps indicative of recent tectonic activity along the SPF, outcrop observations indicate that in some cases both planar and curved normal faults are developed, forming complex fault zones. Sequential development of normal faults may have rotated the early-formed fault blocks, resulting in shallowly dipping faults and highly tilted strata. Collectively, structural similarities probably exit among normal faults at multiple spatial scales. We suggest that the results of this study are also helpful for a better understanding of structural development and evolution in other actively extending areas. [ABSTRACT FROM AUTHOR]