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The East China Sea Shelf Basin (ECSSB) lies at the south‐eastern margin of the Eurasian Plate and was affected by the subduction of the Pacific Plate and the Philippine Plate. It experienced and recorded multistage tectonic inversions in the Cenozoic, especially in the Xihu Sag. In an attempt to investigate the evolution and mechanism of tectonic inversion, this paper presents numerical simulation results by the finite element method to the Xihu Sag. Combined with comprehensive structural analyses of seismic profiles, this paper determines the structural geometry of the sag for establishing a viscoelastic geologic model including six‐layer strata and nine major faults. Simulation results show that the boundary conditions of transtension and transpression control the inversion process that propagates from east to west, and the distribution of low compressive stress displays certain correlations with the distribution of oil deposits. Based on quantitative analysis of the vertical displacement field of the Xihu Sag, this paper identifies a tectonic inversion process, which indicates that the western part of the sag uplifts and the eastern part subsides during the first‐stage inversion; whereas the western part subsides and central‐eastern parts uplift during the second and third stages. The formation of the tectonic inversion is controlled by the adjustment of the stress field from dextral transtension to sinistral transpression caused by the change of subduction rates and direction of the Pacific Plate and the Philippine Sea Plate. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) is a typical Meso-Cenozoic superimposed basin characterized by different tectonic frameworks, suffering multi-stage tectonism (e.g. the Indosinian, the Yanshanian and the Himalayan) since the Mesozoic. The Mesozoic ECSSB is a key place to our understanding of the tectonic evolution and dynamic mechanism in eastern South China and the subduction of the Izanagi Plate. Based on geological and geophysical results acquired over the last 10 years, this paper provides a summary of the distribution of Mesozoic strata, ascertains boundaries of the Mesozoic basin and proposes the division of the Mesozoic tectonic units in the ECSSB. The Mesozoic ECSSB was subdivided into the Western Fault Depression (WFD) characterized by dispersed Cretaceous half-grabens and the East Depression (ED) characterized by depressions at the early stage and grabens at the later stage. The WFD is composed of half-grabens formed under transtension, and the ED is composed of depression zones on the pre-Mesozoic basement under regional compression, indicating different dynamic mechanisms from the Cenozoic basins. Formation of the Mesozoic tectonic framework was controlled by the collision, compression and subduction of the Izanagi Plate and the Pacific Plate and also affected by the Indian Plate at a later stage. By comparison, this paper preliminarily proposes that the northern South China Sea and the ED of the ECSSB were originally a unified basin and jointly constituted a huge Mesozoic proto-basin in the East Asian continental margin. The Mesozoic tectonic unit division is helpful not only to discuss and resolve problems of ocean-continent differences and boundaries in southeastern South China but also to understand the tectonic nature of the East Asian continental margin, the dynamic mechanism of the Mesozoic basins and the transition of continental margin types. It also provides scientific support for petroleum exploration of the Mesozoic strata in the East China Sea. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Based on detailed analysis of the inversion tectonics in each of the secondary tectonic units of the East China Sea Shelf Basin (ECSSB), this paper suggests that the Cenozoic positive inversion tectonics in the basin are typically anticlines of various shapes associated with thrusts. Four stages of tectonic inversions are recognized in the basin related to the Oujiang Movement (T80), the Yuquan Movement (T30), the Huagang Movement (T20) and the Longjing Movement (T12), and these four inversion stages are temporally and spatially distinct. Temporally, the tectonic inversion in the West Depression Group tended to weaken, relatively, from the Oujiang Movement (T80) to the Huagang Movement (T20), while the Longjing Movement (T12) does not show an obvious inversion signature. Spatially, the Longjing Movement tectonic inversion in the Xihu and Diaobei sags of the East Depression Group shows a pronounced reduction in intensity from north to south. The tectonic inversion in the East Depression Group tended to intensify, relatively, from the Yuquan Movement (T30), through the Huagang Movement (T20) to the Longjing Movement (T12). The intensity distribution, migration and evolution of Cenozoic inversions in the ECSSB are local responses to the synthetic effect of the convergence and subduction rates, and direction changes between the Pacific and Eurasian plates and/or between the Indian and Eurasian plates. In particular, the eastward migration of positive inversion tectonics in the ECSSB is closely and successively related to the formation of the East Depression Group and the opening of the Okinawa Trough. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Typhoons are commonly occurring disastrous events in the Western Pacific and have become more severe as the result of global climate changes, increasingly affecting the ocean and seafloor throughout the Western Pacific. However, studies on the influences of typhoon processes and dynamic mechanisms on the continental shelf remain rather limited because of insufficient observational data in the area. This paper uses observational records at a water depth of 110 m on the continental shelf of the East China Sea in the periods when the No. 1323 typhoon 'Fitow' and No. 1324 typhoon 'Danas' passed the East China Sea to study changes in the water temperature, salinity, current and turbidity. Observation results show that typhoon Fitow had limited effects on the measurement site because of the long distance to the centre of the typhoon, but during typhoon Danas, the measured surface current speed reached 2.95 m/s, and the turbidity of the sea water increased rapidly due to the vertical mixing of sea water. Typhoon Danas causes both near-inertial oscillations (NIOs) and diurnal currents to increase, which is considered to be the major factor that contributes to bottom water temperature changes and the suspension of bottom sediments after the passage of the typhoon. Typhoons can also cause the Kuroshio Current to shift towards the continental shelf, which may affect the Tsushima Current. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The oil-gas accumulation process is a tectonic indicator, and the oil-gas trap is generally a result of tectonic movement. In order to explore the law of oil-gas migration and accumulation in the East China Sea Continental Shelf Basin, this paper analyses the dynamic process of hydrocarbon accumulation based on a geological model, taking the Xihu Depression as an example and using the IES PetroMod basin modelling software. Combined with the seismic data and drilling data, the burial history, thermal evolution history and hydrocarbon generation, expulsion and migration history of the Xihu Depression is simulated in this study. The simulation results show that (1) the tectonic framework of the Xihu Depression developed as an inversion structure from an early extensional stage or transtensional faulting stage to a later compressional or transpressional inversion stage; (2) the Pinghu and Huagang formations of the Xihu Depression are still currently at the peak stage of oil-gas generation, and the Xihu Depression is a depression which has abundant hydrocarbon generation and expulsion at a later stage; (3) oil-gas resources vertically migrated to the structural highs from the eastern and western sub-sags along faults and ultimately accumulated in favourable traps, which developed a migration pattern of interbedded sandstone-fault-sandstone like an upward 'staircase'. In particular, faults and the potential energy state played an important role in hydrocarbon migration of the Xihu Depression, which has a guiding significance for understanding hydrocarbon migration and accumulation law and reducing the risk in oil-gas exploration in the East China Sea Continental Shelf Basin. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The central inversion zone in the Xihu Depression, East China Sea, was formed during the Late Miocene. The entire Tertiary succession, nearly 10,000 m thick, has undergone inversion here. The succession is composed mainly of sandstones and mudstones with minor coals and non-marine limestones. Hydrocarbons are present in a series of structural traps which formed as a result of inversion-related deformation. Oil and gas exploration in the Xihu Depressions has demonstrated that at least 90% of the commercial reserves so far found occur in inversion-related structural traps in the central inversion zone, mainly in Eocene (Pinghu Formation) and Oligocene (Huagang Formation) sandstone reservoirs. Previous studies have shown that structural traps are controlled by the intensity and style of inversion tectonics. However, the relationship between the geometry, kinematics and size of the inversion structures and the oil and gas accumulations is not well understood. In this paper, the factors controlling trap formation (and hydrocarbon acumulations) in the study area are considered. Data came from 2D reflection seismic and electic logs from a number of wells. Controlling factors include inversion fault activity rate, inversion rate and the thickness of sediments eroded as a result of inversion-related uplift of the Tertiary succession. The results show that the best exploration targets are located in the southern part of the central inversion zone. This area has a relatively low inversion fault activity rate (average 3.0 m/Ma) and a low inversion rate (average 0.4); a relatively small thickness of sediments was eroded from the Miocene Longjing and Liulang Formations (< 400 m) and the Eocene Pinghu Formation. By contrast, the northern part of the central inversion zone has a relatively high inversion fault activity rate (average 6.8 m/Ma) and a high inversion rate (0.8), and greater thicknesses of sediments were erosively removed (up to 1600 m). This may have resulted in the less favourable preservation of traps and the large-scale leakage of oil and gas. Most oil and gas accumulations occur in the southern part of the central inversion zone, especially in reservoirs in the Longjing, Liulang and Pinghu Formations. [ABSTRACT FROM AUTHOR]