Hasil untuk "Dynamic and structural geology"

Jade Eyles, Jessica Johnson, Jenni Barclay et al.

Volcanic earthquakes provide a wealth of information about the magmatic system. Monitoring volcanic seismicity is one of the primary methods used by volcano observatories globally, including at Soufri`ere Hills Volcano, Montserrat. Computed earthquake locations represent the optimal solution given the information available, and vary depending on the chosen location method and seismic velocity model, but rarely are these parameters tested for suitability in each region. We propose a new method that utilises synthetic earthquakes to evaluate whether the calculated hypocenters and their associated errors accurately represent the true source locations. We define this evaluation as a confidence parameter that highlights events we can 'trust'. By comparing several location methods and seismic velocity models for Montserrat we show the current setup is not optimal, and suggest an alternative location method. Analysis using new 'trusted' relocations focuses on four seismic clusters distal from Soufriere Hills in 1995. Our results highlight differences in hypocenters during this period, suggesting alternative interpretations of the distal seismicity. We propose a WNW dyke orientation supporting previous studies, and local fault complexes in the region. Overall, this paper highlights the importance of using a robust location method suitable for the region to ensure that calculated hypocenters are trustworthy and accurate. Use of sub-optimal methods can influence apparent spatial earthquake trends, impacting interpretations and our understanding of volcanic systems.

Lisa Tomasetto, Pierre Boué, Fabrice Ardhuin et al.

Seismic ambient noise spectra ubiquitously show two amplitude peaks corresponding to distinct oceanic wave interaction mechanisms called primary (seismic period (T) ~ 14 s) and secondary (T ~ 7 s) microseism. Seismic noise records are used in a wide range of applications including crustal monitoring, imaging of the Earth's deep interior using noise correlations, and studies on the coupling between oceans and solid Earth. All of these applications could benefit from a robust knowledge of spatiotemporal dynamics of microseismic sources. Consequently, seismologists have been studying how to model microseismic sources of ambient noise with the recent improvements in ocean wave models. Global sea state and its derivative products are now covering the past decades in models such as the WAVEWATCHIII hindcast. This paper introduces the Wave Model Sources of Ambient Noise (WMSAN, pronounced [wam-san]) Python package. This modular package uses standardized wave model outputs to visualize ambient noise source maps and efficiently compute synthetics of seismic spectrograms and cross-correlations for surface waves (Rayleigh) and body waves (P, SV), in a user-friendly way.

M. Altmann, M. Pfeiffer, F. Haas et al.

<p>We show a long-term erosion monitoring of several geomorphologically active gully systems on Little Ice Age lateral moraines in the European Central–Eastern Alps, covering a total time period from 1953 to 2019 and including several survey periods in order to identify corresponding morphodynamic trends. For the implementation, DEM (digital elevation model) of Differences (DoDs) were calculated, based on multitemporal high-resolution digital elevation models from historical aerial images (generated by structure from motion photogrammetry with multi-view stereo) and light detection and ranging from airborne platforms. Two approaches were implemented to achieve the corresponding objectives. First, by calculating linear regression models using the accumulated sediment yield and the corresponding catchment area (on a log–log scale), the range of the variability in the spatial distribution of erosion values within the sites. Second, we use volume calculations to determine the total and the mean sediment yield (as well as erosion rates) of the entire sites. Subsequently, both the sites and the different time periods of both approaches are compared. Based on the slopes of the calculated regression lines, it can be shown that the highest variability in the sediment yield at the sites occurs in the first time period (mainly 1950s to 1970s). This can be attributed to the fact that within some sites the sediment yield per square metre increases clearly more strongly (regression lines with slopes up to 1.5). In contrast, in the later time periods (1970s to mid-2000s and mid-2000s to 2017/2019), there is generally a decrease in 10 out of 12 cases (regression lines with slopes around 1). However, even at sites with an increase in the variability in the sediment yield over time, the earlier high variabilities are no longer reached. This means that the spatial pattern of erosion in the gully heads changes over time as it becomes more uniform. Furthermore, using sediment volume calculations and corresponding erosion rates, we show a generally decreasing trend in geomorphic activity (amount of sediment yield) between the different time periods in 10 out of 12 sites, while 2 sites show an opposite trend, where morphodynamics increase and remain at the same level. Finally, we summarise the results of long-term changes in the morphodynamics of geomorphologically active areas on lateral moraines by presenting the “sediment activity concept”, which, in contrast to theoretical models, is based on actually calculated erosion. The level of geomorphic activity depends strongly on the characteristics of the sites, such as size, slope length, and slope gradient, some of which are associated with deeply incised gullies. It is noticeable that especially areas with influence of dead ice over decades in the lower slope area show high geomorphic activity. Furthermore, we<span id="page400"/> show that system internal factors, as well as the general paraglacial adjustment process, have a greater influence on long-term morphodynamics than changing external weather and climate conditions, which, however, had a slight impact mainly in the last, i.e. most recent, time period (mid-2000s to 2017/2019) and may have led to an increase in erosion at the sites.</p>

A. Snyder, N. Prime, C. Tebaldi et al.

<p>Earth system models (ESMs) and general circulation models (GCMs) are heavily used to provide inputs to sectoral impact and multisector dynamic models, which include representations of energy, water, land, economics, and their interactions. Therefore, representing the full range of model uncertainty, scenario uncertainty, and interannual variability that ensembles of these models capture is critical to the exploration of the future co-evolution of the integrated human–Earth system. The pre-eminent source of these ensembles has been the Coupled Model Intercomparison Project (CMIP). With more modeling centers participating in each new CMIP phase, the size of the model archive is rapidly increasing, which can be intractable for impact modelers to effectively utilize due to computational constraints and the challenges of analyzing large datasets. In this work, we present a method to select a subset of the latest phase, CMIP6, featuring models for use as inputs to a sectoral impact or multisector dynamics models, while prioritizing preservation of the range of model uncertainty, scenario uncertainty, and interannual variability in the full CMIP6 ensemble results. This method is intended to help impact modelers select climate information from the CMIP archive efficiently for use in downstream models that require global coverage of climate information. This is particularly critical for large-ensemble experiments of multisector dynamic models that may be varying additional features beyond climate inputs in a factorial design, thus putting constraints on the number of climate simulations that can be used. We focus on temperature and precipitation outputs of CMIP6 models, as these are two of the most used variables among impact models, and many other key input variables for impacts are at least correlated with one or both of temperature and precipitation (e.g., relative humidity). Besides preserving the multi-model ensemble variance characteristics, we prioritize selecting CMIP6 models in the subset that preserve the very likely distribution of equilibrium climate sensitivity values as assessed by the latest Intergovernmental Panel on Climate Change (IPCC) report. This approach could be applied to other output variables of climate models and, possibly when combined with emulators, offers a flexible framework for designing more efficient experiments on human-relevant climate impacts. It can also provide greater insight into the properties of existing CMIP6 models.</p>

M. Correia, M. Maleki, Felipe Bruno Mesquita da Silva et al.

The geological features revealed by well production data or 4D Seismic are often neglected in data assimilation or disconnected from the geomodelling tasks through simplifications on static and dynamic data. This work provides a workflow to accurately integrate 4D seismic insights through a forward geomodelling approach and provides prior simulation models calibrated with observed dynamic data. The methodology follows four steps: (1) develop the geological model, (2) generate equiprobable geostatistical realisations based on the multiple stochastic approach, (3) apply the DLHG method (Discretized Latin Hypercube combined with Geostatistics), and (4) validate the geological consistency and uncertainty quantification using the observed dynamic data. The methodology is applied to a real turbiditic reservoir, a heavy oil field in the offshore Campos Basin, Brazil. From the 4D seismic datasets, the following data was available: (1) base survey, (2) monitor-2016, and (3) monitor-2020. The interpreted 4D seismic trends were integrated in the geological model by combining the geometrical modelling technique, for observed structural features, with the objects’ modelling approach, for the observed sand channels. The geostatistical realisations were then combined with dynamic uncertainties through the DLHG method. The quantitative validation based on the NQDS indicator showed that the generated prior simulation models encompass the observed production data. In addition, the match with observed 4D seismic data based on dRMS amplitude maps highlighted the value of adding 4D seismic information. This paper presents a successful forward modelling approach to highlight the value of 4D seismic on the calibration of simulation models prior to data assimilation.

M. Su, Feng Qian, Shengkai Cui et al.

The core challenges to automatic full-horizon tracking are how to establish a potential local connection relationship between the horizon points, conduct accurate global diffusion in a three-dimensional space, and finally, how to form a complex horizon surface. The existing attribute-based horizon-tracking methods based on waveform similarity, dip guidance, and RGT (relative geological time) can not solve the problems of local connection and global diffusion at the same time. In view of this challenge, this paper proposes an automatic 3D seismic horizon-tracking method based on global corrugated diffusion, which can completely integrate local connection and global diffusion so that all horizons in the whole data volume can be interpreted simultaneously. For the problem of local horizon-point connection, this paper uses the correlation between seismic trace pairs based on DTW (dynamic time warping) correlation to mine the connection mode between horizon points. For the global diffusion problem, this paper proposes the realization of global modeling based on the relationship between seismic samples, constructing a complex 3D horizon through a central ripple-diffusion process. The example shows that the horizon tracked by this method well reflects the original stratum occurrence and stratum-contact relationship, retains the structural details, accurately reflects the structural shape, and realizes automatic tracking across faults.

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Behzad Dastjerdy, Ali Saeidi, Shahriyar Heidarzadeh

The reliability of geomechanical models and engineering designs depend heavily on high-quality data. In geomechanical projects, collecting and analyzing laboratory data is crucial in characterizing the mechanical properties of soils and rocks. However, insufficient lab data or underestimating data treatment can lead to unreliable data being used in the design stage, causing safety hazards, delays, or failures. Hence, detecting outliers or extreme values is significant for ensuring accurate geomechanical analysis. This study reviews and categorizes applicable outlier detection methods for geomechanical data into fence labeling methods and statistical tests. Using real geomechanical data, the applicability of these methods was examined based on four elements: data distribution, sensitivity to extreme values, sample size, and data skewness. The results indicated that statistical tests were less effective than fence labeling methods in detecting outliers in geomechanical data due to limitations in handling skewed data and small sample sizes. Thus, the best outlier detection method should consider this matter. Fence labeling methods, specifically, the medcouple boxplot and semi-interquartile range rule, were identified as the most accurate outlier detection methods for geomechanical data but may necessitate more advanced statistical techniques. Moreover, Tukey’s boxplot was found unsuitable for geomechanical data due to negative confidence intervals that conflicted with geomechanical principles.

Safaa Manfi Alshibany, Saif Alzabeebee, Suraparb Keawsawasvong

Tire-derived aggregate (TDA) has been used successfully as a backfill soil to reduce the applied stresses on buried steel pipes. The preceding study, however, paid no attention to inspecting the TDA efficiency of buried concrete pipes subjected to soil and traffic loads. In addition, it is not clear how the TDA material, traffic loading, burial depth, and road section affect the pipe-bending moment. Therefore, this paper examines the efficiency of TDA in reducing the bending moment of a 0.6 m concrete pipe subjected to combined soil and traffic loads using a validated three-dimensional finite element model. Two trench configurations have been constructed, the first is composed completely of well graded sand, and the second is similar to the first except for the 150 mm layer on the top of the pipe crown, which is replaced with TDA. Furthermore, three road sections (highway, public road, and unpaved road) have been adopted to provide an intensive understanding of the TDA effect for different road conditions. A parametric study is carried out to detect the effect of the burial depth, road section, and traffic load on the efficiency of the TDA of the buried pipe. It is observed that the TDA has no effect on the bending moment distribution around the pipe. Additionally, the TDA reduces the bending moment developed in the pipe wall with a percentage decrease range between 18% and 42% depending on the burial depth and road section. Furthermore, it is also found that the efficiency of the TDA in reducing the maximum bending moment decreases as the burial depth increases. In addition, the best performance for the TDA is found at a burial depth of 1.0 m for all road sections. Importantly, the best performance for the TDA is found for the highway section compared with the other sections, with a maximum percentage decrease of 42% compared to 27% for the public road section and 26% for the unpaved road section.

Wenbiao Li, Shuangfang Lu, Junqian Li et al.

Abstract Methane transportation in tight sedimentary rocks results in significant and complex isotope fractionation. Existing models and mechanistic studies of isotope fractionation cannot fully explain the actual observations in gas transport processes that occur in natural reservoirs and in the laboratory. Thus, geological applications based on transport-related isotope fractionation have been lacking in substantive progress. Here, we established a multi-scale model in which seepage in fractures, diffusion and adsorption/desorption in matrix pores, and concentration diffusion in kerogen structural pores are coupled. The results show that both diffusion and adsorption/desorption lead to significant isotope fractionation, while the contribution of pressure-driven seepage, is limited. The diffusion of kerogen-dissolved gas is of considerable significance to isotope fractionation in the later stage of transport, despite its weak contribution to gas production. The sequence of controlling factors of isotope fractionation during pure diffusion is as follows: diffusion coefficient ratio (D⁎/D) > initial pressure (P0) > others, where the value of D⁎/D mainly depends on the average pore size of rocks. The isotope fractionation caused by adsorption/desorption is closely related to the Langmuir parameters of sedimentary rock. It is essentially a dynamic non-equilibrium fractionation during adsorbed gas transport, rather than thermodynamic equilibrium fractionation between adsorbed gas and free gas. The model developed herein determines the contribution of each single effect to the apparent isotope fractionation and provides a novel method for obtaining the Langmuir parameters of rocks under in-situ geological conditions. Under variable boundary conditions, this model can be used to evaluate the gas resource potential and recoverable reserves in unconventional reservoirs and demonstrates the great potential for monitoring the production status of shale gas wells.

Baoli Tang, Yongqiang Ren

Tunnel construction is gradually developing to areas with high in situ stress; the deeper the tunnel construction, the more intense the earthquake disturbance. Under the background of frequent earthquakes, the seismic characteristics of tunnels become an important content related to the safety and stability of engineering structures. In view of the key problems of seismic response and vibration reduction measures for complex deep buried tunnels, the methods of advanced grouting and foam concrete aseismic are studied in this paper. Firstly, through geological survey, the in situ stress and geological conditions of the study area are analyzed. The structural characteristics of surrounding rock and related rock mechanics parameters are analyzed. The failure criterion of concrete lining under dynamic load is studied theoretically, and the relevant numerical calculation parameters are modified. A numerical model based on viscous boundary conditions is established. Through numerical calculation, the seismic response of tunnel surrounding rock and lining under different damping measures is analyzed. The research results have theoretical research value and social and economic benefits for ensuring the safety and stability of tunnel structure and improving the seismic fortification level.

M. De Lucia, M. Kühn, M. Kühn

<p>Advances in computing and experimental capabilities in the research of water-rock-interactions require geoscientists to routinely combine laboratory data and models to produce new knowledge. Data science is hence a more and more pervasive instrument for geochemists, which in turn demands flexible and easy to learn software adaptable to their specific needs. The GNU R language and programming environment has established itself as de facto standard language for statistics and machine learning, enjoying increasing diffusion in many applied scientific fields such as bioinformatics, chemometrics and ecological modelling. The availability of excellent third party extensions as well as its advanced graphical and numerical capabilities make R an ideal platform for comprehensive geochemical data analysis, experiment evaluation and modelling.</p> <p>We introduce the open source <code>RedModRphree</code> extension package, which leverages the R interface to the established <code>PHREEQC</code> geochemical simulator. The aim of <code>RedModRphree</code> is to provide the user with an easy-to-use, high-level interface to program algorithms involving geochemical models: parameter calibration, error and sensitivity analysis, thermodynamical database manipulation, up to CPU-intensive parallel coupled reactive transport models. Among the out-of-the-box features included in <code>RedModRphree</code>, we highlight the computation and visualization of Pourbaix (Eh-pH) diagrams using full speciation as computed by <code>PHREEQC</code> and the implementation of 1D advective reactive transport supporting the use of surrogate models replacing expensive equation-based calculations.</p>

J. Lai, J. Lai, A. M. Anders

<p>Climate has been viewed as a primary control on the rates and patterns of glacial erosion, yet our understanding of the mechanisms by which climate influences glacial erosion is limited. We hypothesize that climate controls the patterns of glacial erosion by altering the basal thermal regime of glaciers. The basal thermal regime is a first-order control on the spatial patterns of glacial erosion. Polythermal glaciers contain both cold-based portions that protect bedrock from erosion and warm-based portions that actively erode bedrock. In this study, we model the impact of various climatic conditions on glacier basal thermal regimes and patterns of glacial erosion in mountainous regions. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of the glacier basal thermal regime and glacial erosion in a synthetic landscape. We find that both basal thermal regimes and glacial erosion patterns are sensitive to climatic conditions, and glacial erosion patterns follow the patterns of the basal thermal regime. Cold temperature leads to limited glacial erosion at high elevations due to cold-based conditions. Increasing precipitation can overcome the impact of cold temperature on the basal thermal regime by accumulating thick ice and lowering the melting point of ice at the base of glaciers. High precipitation rates, therefore, tend to cause warm-based conditions at high elevations, resulting in intensive erosion near the peak of the mountain range. Previous studies often assessed the impact of climate on the spatial patterns of glacial erosion by integrating climatic conditions into the equilibrium line altitudes (ELAs) of glaciers, and glacial erosion is suggested to be maximal around the ELA. However, our results show that different climatic conditions produce glaciers with similar ELAs but different patterns of basal thermal regime and glacial erosion, suggesting that there might not be any direct correlation between ELAs and glacial erosion patterns.</p>

M. Häusler, P. R. Geimer, R. Finnegan et al.

<p>Natural rock arches are rare and beautiful geologic landforms with important cultural value. As such, their management requires periodic assessment of structural integrity to understand environmental and anthropogenic influences on arch stability. Measurements of passive seismic vibrations represent a rapid and non-invasive technique to describe the dynamic properties of natural arches, including resonant frequencies, modal damping ratios, and mode shapes, which can be monitored over time for structural health assessment. However, commonly applied spectral analysis tools are often limited in their ability to resolve characteristics of closely spaced or complex higher-order modes. Therefore, we investigate two techniques well-established in the field of civil engineering through application to a set of natural arches previously characterized using polarization analysis and spectral peak-picking techniques. Results from enhanced frequency domain decomposition and parametric covariance-driven stochastic subspace identification modal analyses showed generally good agreement with spectral peak-picking and frequency-dependent polarization analyses. However, we show that these advanced techniques offer the capability to resolve closely spaced modes including their corresponding modal damping ratios. In addition, due to preservation of phase information, enhanced frequency domain decomposition allows for direct and convenient three-dimensional visualization of mode shapes. These techniques provide detailed characterization of dynamic parameters, which can be monitored to detect structural changes indicating damage and failure, and in addition have the potential to improve numerical models used for arch stability assessment. Results of our study encourage broad adoption and application of these advanced modal analysis techniques for dynamic analysis of a wide range of geological features.</p>

J. Watt, D. Brothers

Studies of recent destructive megathrust earthquakes and tsunamis along subduction margins in Japan, Sumatra, and Chile have linked forearc morphology and structure to megathrust behavior. This connection is based on the idea that spatial variations in the frictional behavior of the megathrust influence the tectono-morphological evolution of the upper plate. Here we present a comprehensive examination of the tectonic geomorphology, outer wedge taper, and structural vergence along the marine forearc of the Cascadia subduction zone (offshore northwestern North America). The goal is to better understand geologic controls on outer wedge strength and segmentation at spatial scales equivalent to rupture lengths of large earthquakes (≥M 6.7), and to examine potential linkages with shallow megathrust behavior. We use cross-margin profiles, spaced 25 km apart, to characterize along-strike variation in outer wedge width, steepness, and structural vergence (measured between the toe and the outer arc high). The width of the outer wedge varies between 17 and 93 km, and the steepness ranges from 0.9° to 6.5°. Hierarchical cluster analysis of outer wedge width and steepness reveals four distinct regions that also display unique patterns of structural vergence and shape of the wedge: Vancouver Island, British Columbia, Canada (average width, linear wedge, seaward and mixed vergence); Washington, USA (higher width, concave wedge, landward and mixed vergence); northern and central Oregon, USA (average width, linear and convex wedge, mixed and seaward vergence); and southern Oregon and northern California, USA (lower width, convex wedge, seaward and mixed vergence). Variability in outer wedge morphology and structure is broadly associated with along-strike megathrust segmentation inferred from differences in oceanic asthenospheric velocities, patterns of episodic tremor and slow slip, GPS models of plate locking, and the distribution of seismicity near the plate interface. In more detail, our results appear to delineate the extent, geometry, and lithology of dynamic and static backstops along the margin. Varying backstop configurations along the Cascadia margin are interpreted to represent material-strength contrasts within the wedge that appear to regulate the along- and across-strike taper and structural vergence in the outer wedge. We argue that the morphotectonic variability in the outer wedge may reflect spatial variations in shallow megathrust behavior occurring over roughly the last few million years. Comparing outer wedge taper along the Cascadia margin to a global compilation suggests that observations in the global catalog are not accurately representing the range of heterogeneity within individual margins and highlights the need for detailed margin-wide morphotectonic analyses of subduction zones worldwide.

Ze Liu, L. Dai, San-zhong Li et al.

Abstract The interaction between the Earth's surface and deep geodynamic processes has a great influence on sedimentary patterns and characteristics of sedimentary systems, especially in the continental margin, such as the southern part of the East China Sea Continental Shelf Basin (ECSCSB). However, the exact processes and dynamics are poorly understood. The numerical tool (Badlands) was adopted to simulate the geological evolution of the southern ECSCSB during the Mesozoic transitional regime of the West Pacific continental margin, between 200 and 100 Ma. The numerical model involving four-dimensional (4D) sequence stratigraphy was validated by comparing with the tectono-morphology, sedimentary environments and sediment distribution. According to our findings, the transition was mainly controlled by three structural stages. The first transitional stage of the southern ECSCSB was mainly controlled by lithospheric-scale tectonic evolution. In the second stage, the dynamic topography contributed to slow regional uplift, while the last stage showed mantle-induced dynamic subsidence. The model results on 4D geomorphic characteristics, sediment distribution of basin evolution and deep dynamic topography, provided a quantitative image for geological evolution of the West Pacific continental margin in the Mesozoic.

B. S. Bali, Ahsan Afzal Wani

M. Pagliai, Marina Macchiagodena, P. Procacci et al.

Water has a fundamental role in important processes spanning a wide range of pressure and temperature conditions. Knowledge of structural, dynamic and thermodynamic properties of water at non-standard conditions is a primary concern since interest on astronomical, geological and technological processes is continuously growing. Molecular dynamics simulations allow to study thermodynamic conditions which require sophisticate techniques and instruments, while at the same time offering the interpretation of properties at atomic level. It is established that the behavior of water is strongly affected by the temperature and pressure conditions, determining the existence of low and high density regimes. For the first time a thermodynamic property, isothermal compressibility, has been adopted to detect the low-high density turning point at ambient temperature in liquid water due to pressure. Molecular dynamics simulations have been performed with five three-site models, allowing to characterize the complexity of water nature at these conditions at atomic level.

A. Beskopylny, A. Lyapin, M. Kadomtsev et al.

The article presents a comprehensive method for diagnosing underground structures using the example of an underground pedestrian crossing located in Rostov-on-Don. The problem of assessing the condition of buildings and structures is very relevant at all stages of the life cycle. There is a special need for continuous monitoring of bearing structures for many buildings with critical applications especially if reliability of which determines the life and health of people. This work considered complex method included geodetic research, geological study of the state of sub-soil, analysis of state of steel and reinforced concrete structures, vibro diagnostics of load-bearing structures under dynamic technogenic impacts and an assessment of the mechanical characteristics of steel and reinforced concrete structures in order to develop a conclusion on the overall state of the transition and the possibility of its further operation. Analysis of the response from arbitrary non-stationary effects on structural elements is carried out on the base of the calculated spectrum of reference impacts.

Changqing Yang, Baofu Han, Chuansheng Yang et al.

The East China Sea Shelf Basin (ECSSB) is located on the south‐eastern edge of the Eurasian Plate. The tectono‐evolution and dynamic mechanism of the ECSSB are related to the collision of the Pacific Plate with the Eurasian Plate, and the remote pushing effect of the Indo‐Australian Plate remains a hot topic of debate. Based on the latest survey data, this paper mainly focuses on the evolution of the Mesozoic basin in the East China Sea Shelf by means of assessing the regional tectonic background, conducting structural physical simulation experiments, and applying balanced geological section recovery technology to discuss the processes of dynamic transition in Southeast China. Our data suggest that the ECSSB experienced an evolutionary sequence involving the pre‐Late Triassic passive continental margin; the Late Triassic–Middle Jurassic active continental margin extrusion‐depression; the extrusional stress from the low‐angle subduction of the Izanaki Plate under the Eurasian Plate; the late Early Cretaceous to Late Cretaceous active continental marginal extension faulted basin, during which the extensional stress originated from the lithospheric thinning and palaeoenvironment resulting from the subduction of the Palaeo‐Pacific Plate under the Eurasian Plate; and the Palaeogene back‐arc extension faulted sags. The transition time from the E‐W‐trending Palaeo‐Tethys tectonic system to the NE‐trending Palaeo‐Pacific tectonic system in Southeast China occurred at the end of the Middle Triassic. The low‐angle subduction and withdrawal of subduction of the Palaeo‐Pacific Plate probably represented the deep geological processes of the Mesozoic in Southeast China.