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The Guizhou Province is located in karst mountainous area, so it is very important for the future layout and planning of the city to study the underground geological structure of the city based on seismic detection technology. In this paper, taking the underground active fault detection in the Liupanshui City, Guizhou Province, China as an example, a set of appropriate evaluation techniques for the accurate spatial location, structural characteristics and latest activities of the fault suit for mountainous area are proposed. Through pre-stack noise suppression, amplitude fidelity and consistency processing, and multiple iterative analysis of velocity residual statics, the resolution of the geological structure of the underground rock has been significantly improved. Based on the detailed interpretation of the shallow seismic data and the regional geological analysis, it is concluded that the main fault strike of the Weining – Shuicheng section of the Weining - Shuicheng fault is NW, mainly normal fault, the dip direction is mainly southwest, partly northeast and the dip angle is 60-70°. The strata of the two fault plates are strongly compressed and broken, and the limestone and dolomite are generally recrystallized, and calcite veins and masses can be seen. [ABSTRACT FROM AUTHOR]

The Wudaoliang–Changshagongma fault is one of the NW-trending faults located within the southern Bayan Har Block of the Tibetan Plateau in China. In this paper, we used high-resolution imagery and digital elevation model data to study the geomorphological and geological characteristics of the fault. Furthermore, the result also determined the fault trace and estimated the average horizontal slip rate of the fault since the late Quaternary to have been 2.6 ± 0.6 mm/a. This slip rate is approximately equivalent to that of the Awancang, Madoi–Garde, and Dari faults, which are also located within the block. Furthermore, the slip rates of these faults obtained by remote sensing and geological methods are consistent with GPS observations. It indicates that tectonic deformation within the block is continuous and diffuse. Using trenching study results and sedimentary radiocarbon dating, we identified four paleoearthquake events that occurred at 42,378–32,975, 33,935–20,663, 5052–4862, and after 673–628 cal BP, respectively. The recurrence intervals of large earthquakes on the faults within the block are much longer than those of the boundary faults, and the slip rates are also smaller, indicating that faults within the block play a regulatory role in the tectonic deformation of the Bayan Har Block. [ABSTRACT FROM AUTHOR]

The observation of electromechanical coupling might be used as an important tool to detect pre-seismic changes associated with the preparation of earthquakes. This paper attempts to study the electromechanical coupling process before the large earthquakes by using the load/unload response ratio (LURR) approach in which the geo-electric data and Benioff strain of small earthquakes were adopted as the data input. The variation of Coulomb failure stress induced by earth tides on the fault surface of the mainshock is applied to differentiate the loading and unloading stages. Using this technique, we test the geo-electric data recorded at the Hotan observatory near the epicenter of 2020 Yutian Ms 6.4 earthquake. Results show that the LURR time sequence fluctuated around 1.0 for many years and reached significant high peaks at the beginning of 2020. More importantly, this evolution correlates well with the LURR time series calculated by using the Benioff strain of small earthquakes within the circular region of 300 km radius centered at the epicenter. The underlying physics of the changes should be caused by the fluid infiltration derived from pre-seismic rock dilatancy. The corresponding volume variations in the crust could be found in the geophysical observation time series in the same neighborhoods. [ABSTRACT FROM AUTHOR]

A preliminary study of the PGA attenuation, hanging wall effect and velocity pulse characteristics from the 2008 Wenchuan earthquake of M8 =8.0 is described in this paper. The study was carried out through analyses in the time and frequency domains of main earthquake records. In the PGA attenuation study, records from 316 stations less than 1000 km from the surface rupture of the fault were used as a database and attenuation relationships were developed and compared with some existing relationships that are widely used in mainland China, Chinese Taiwan and the US. At the same time, records from 28 stations less than 100 km from the fault were used to study the hanging wall effect and velocity pulse characteristics of this earthquake based on the distribution of PGA, PGV, spectral acceleration, and the velocity pulse peak, and the results are compared with the 1999 Chi-Chi earthquake. In addition, the large PGAs of the UD components observed in this event are also discussed in this paper. From the results of the preliminary study, some conclusions are developed and suggestions for further research are proposed. [ABSTRACT FROM AUTHOR]

Radon and mercury concentrations were measured in 10 fault gas profiles in Generalized Haiyuan Fault. This paper aims to predetermine the potential seismic risk in different segments of the fault zone from the perspective of geochemistry. The background value and anomaly threshold were adopted and synthesized using the maximum value method and average method to calculate concentration intensity values of radon and mercury. Fault soil gas mercury and radon concentrations show a decreasing gradient from NW to SE indicating evident segmentation. Higher values are mostly distributed in the Maomao Mountain-Tiger Mountain fault and Jingtai area. Combined with the seismotectonic background of historical and recent earthquakes and the spatial distribution characteristics of b-values, the fault soil gas concentration intensity shows a close correlation with earthquake activity within the fault zone. Concentrations of fault gas are higher and the b-value lower in areas of strong seismic activity, and regions with weak seismic activity correspond to lower fault gas concentrations and higher b-values. It is thus considered that the Jingtai area may be more dangerous than the other areas. This paper could provide vital background information for earthquake prediction in the Generalized Haiyuan Fault Zone. [ABSTRACT FROM AUTHOR]

This paper presents results of recent studies on distribution and category of landslides in one section of the Sichuan–Tibet Highway, adjacent to the northern side of the Yarlu Tsangpo Grand Canyon, Tibet, Southwestern China. In the tectonic setting predominated by compression and strike-slipping, active faults are dominant and result in the genesis of the great alpine relief together with fluvial incision and unloading. In this section, with a distance of about 290 km between Ranwu and Lulang, 34 landslides occurred. Among them, the 12 large and super-large landslides comprise the most dangerous part of the highway system to road users over the past 50 years. The landslides usually occurred in slopes comprised of moraine with a large thickness, fluvio-pluvial and lacustrine deposits and fractured rocks. Based on the examination of the physical geography, structural geology, Quaternary geology, stratigraphy and petrography, this paper presents the temporal-spatial distribution of landslides along the section and classification of them into three types with respect to mechanism and composites of landslides. Each of the three types is presented by distinctive case examples. Type 1 is Yigong Landslide; type 2 includes Dongjiu Landslide group, 102 Landslide group, Suotong Landslide group, Songzong Landslide; and the type 3 is Layue Landslide. A binary landslide, which is seldom seen in nature and which occurred in the outlet of one creek under the integrative function of fluvial incision and road cut, is also presented. These are distributed in different parts of the area with characterized structural geology, topography and composites (gneiss and Quaternary deposits) with accumulative quantity between Suotong and Dongjiu. The most occurred with frequent and rapid translation, shallow shearing planes, various influential factors and unique triggering factors, and a variable period of reoccurrence with a tendency of increasing magnitude. In this region, six influential factors greatly contribute to their occurrence: (a) intensive neotectonic movements, (b) ongoing alpine canyon relief, (c) earthquakes, (d) heavy precipitation, (e) stream erosion, and (f) human activities, to a certain extent. Mostly, the latter four factors play major roles in triggering landslide occurrence. The earthquake causes the rock and soil to fracture and deform, and tends to be unstable, or cause earth-induced landslides. The heavy rainfall in monsoon seasons which saturates the soil and lower the shearing strength is mostly responsible for the occurrence of landslides. The stream erosion disturbs slope toes causing progressive failure. Road construction and deforestation decrease the natural slope stability. Comments and suggestions on the physical measures for remediation of landslides and safety of highways are also made. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin lies between the Pacific Subduction and Indian-Eurasian Collision tectonic domains and records Cenozoic tectonic inversion, especially in the Xihu Sag. To improve the understanding of the evolution and mechanism of tectonic inversion, this paper employs analogue modelling to reproduce the evolutionary process. Combined with the structural analysis of seismic profile, this paper determines the pattern of basement-involved faults. Simulation results show that under the transtension, two subsidence centers developed and a number of normal faults assembled in two flower structures. When the stress field turned into transpression, the geometry and deformation of inversion basin inherited the previous transtensional basin and pre-existing faults, respectively. The geometry and fault patterns in models are well consistent with those observed in the Xihu Sag, which indicates the plausibility of similar deformation controls. The formation of the tectonic inversion is related to the variation in stress field caused by the changes in the rates and directions of the subduction of the Pacific Plate and the collision of the Indian Plate with Eurasian Plate. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the application of an airborne gravity survey to sedimentary basin analysis. Using high-precision airborne gravity data constrained by drilling and seismic data from the Bohai Bay Basin in eastern China, we interpreted faults, structural elements, sedimentary thickness, structural styles and local structures (belts) in the central area of the Basin by the wavelet transform method. Subsequently, these data were subtracted from the Bouguer gravity to calculate the residual gravity anomalies. On this basis, the faults were interpreted mainly by linear zones of high gravity gradients and contour distortion, while the sedimentary thicknesses were computed by the Euler deconvolution. The structural styles were identified by the combination of gravity anomalies and the local structures interpreted by the first vertical derivative of the residual gravity. The results showed evidence for seven faults, one sag and ten new local structure belts. [ABSTRACT FROM AUTHOR]

The shifting correlation method (SCM) is proposed for statistical analysis of the correlation between earthquake sequences and electromagnetic signal sequences. In this method, the two different sequences were treated in units of 1 day. With the earthquake sequences fixed, the electromagnetic sequences were continuously shifted on the time axis, and the linear correlation coefficients between the two were calculated. In this way, the frequency and temporal distribution characteristics of potential seismic electromagnetic signals in the pre, co, and post-seismic stages were analyzed. In the work discussed in this paper, we first verified the effectiveness of the SCM and found it could accurately identify indistinct related signals by use of sufficient samples of synthetic data. Then, as a case study, the method was used for analysis of electromagnetic monitoring data from the Minxian-Zhangxian M 6.5 ( M 6.1) earthquake. The results showed: (1) there seems to be a strong correlation between earthquakes and electromagnetic signals at different frequency in the pre, co, and post-seismic stages, with correlation coefficients in the range 0.4-0.7. The correlation was positive and negative before and after the earthquakes, respectively. (2) The electromagnetic signals related to the earthquakes might appear 23 days before and last for 10 days after the shocks. (3) To some extent, the occurrence time and frequency band of seismic electromagnetic signals are different at different stations. We inferred that the differences were related to resistivity, active tectonics, and seismogenic structure. [ABSTRACT FROM AUTHOR]

The Erguna Fault runs along the east bank of the Erguna River in NE China and is a large-scale ductile shear zone comprising granitic mylonites. This paper reports on the geometry, kinematic indicators, and Ar/Ar biotite ages of the granitic mylonites,to constrain the structural characteristics, forming age, and tectonic attribute of the Erguna ductile shear zone. The zone strikes NE and records a top-to-the-NW sense of shear. A mylonitic foliation and stretching lineation are well developed in the mylonites, which are classified as S-L tectonites. Logarithmic flinn parameters (1.18-2.35) indicate elongate strain which approximatesto plane strain. Kinematic vorticity numbers are 0.42-0.92 and 0.48-0.94, based on the polar Mohr diagram and the oblique foliation in quartz ribbons, respectively, suggesting that the ductile shear zone formed under general shear, or a combinationof simple and pure shear. According to finite strain and kinematic vorticity analyses, the Erguna Fault is a lengthening-thinning ductile shear zone that formed by extension. The deformation behavior of minerals in the mylonites indicates that the fault was the site of three stages of deformation: an initial stage of middle- to deep-level, high-temperature shear, a post-stress recovery phase of high-temperature static recrystallization, and a final phase of low-temperature uplift and cooling. The Ar/Ar plateau ages of biotite from the granitic mylonites are 106.16 ± 0.79 and 111.55 ± 0.67 Ma, which constrain the timing of low-temperature uplift and cooling but are younger than the ages of metamorphic core complexes (MCCs) in the Transbaikalia-northeast Mongolia region. Using measured geological sections, microtectonics, estimates of finite strain and kinematic vorticity, and regional correlations and geochronology, we conclude that the Erguna Fault is an Early Cretaceous, NNE-trending, large-scale, sub-horizontal, and extensional ductile shear zone. It shares a similar tectonic background with the MCCs, volcanic fault basins, and large and super-large volcanic-hydrothermal deposits in Transbaikalia-northeast Mongolia and the western Great Khingan Mountains, all of which are the result of overthickened crust that gravitationally collapsed and extended in the Early Cretaceous after plate collision along the present-day Sino-Russia-Mongolia border tract. [ABSTRACT FROM AUTHOR]

The lithosphere of the North China Craton (NCC) has experienced significant destruction and deformation since the Mesozoic, a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC. Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes, a three-dimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data, and its relationship with the extensional structures and the formation of rifts was further analyzed. Our results show that the western NCC is characterized by thick lithosphere, low Moho temperature (TMoho<600°C), as well as high lithospheric strength and mantle-crust strength ratio (Sm/Sc>1). The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle. On the other hand, the lithosphere in the eastern NCC is characterized by extensive thinning (with lithospheric thickness of about 80–110 km). However, the decrease of lithospheric strength is not uniform, with high strength (10×1012 Pa m) observed in some areas (such as the Bohai Bay Basin and Hehuai Basin). Most of the eastern lithosphere is characterized by high TMoho (600–750°C) and low Sm/Sc (<1), which is inconsistent with the widespread extensional structure in the eastern NCC. Incorporating results from palaeo-geothermal and petrological studies, we developed a thermo-rheological structure model of the lithosphere at different evolutionary stages of the NCC, and suggested that the eastern NCC had a significantly thinned and weakened lithosphere in the early stages of the formation of the rift, leading to a regional distributed extension deformation dominated by crustal strength, which eventually evolved into a series of wide rifts. However, the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle, resulting in the inconsistency between the present thermo-rheological structure of the lithosphere and the extensional structure formed in the past. [ABSTRACT FROM AUTHOR]

The Junggar Basin is one of the main oil basins in Northwest China, and the north‐west part of the basin is a significant petroleum exploration target. Mesozoic structural activity had an important influence on the present structural characteristics of the north‐west Junggar Basin. In this paper, we discuss the tectonic evolution of the Junggar Basin by studying the structural characteristics of the Ke‐Bai Fault. Our results suggest that the Ke‐Bai Fault has obvious strike‐slip characteristics and that it is an important basin‐controlling fault that has controlled the tectonic evolution of the north‐west Junggar Basin. The Junggar Basin was a rift basin in the Early Permian, but it experienced a tectonic reversal during the Middle Permian to the Triassic. The Ke‐Bai Fault changed from a normal fault into a thrust fault from the Early Permian to the Triassic. During the Jurassic, dextral strike‐slip structures developed along the Ke‐Bai Fault, horsetail splay faults developed in its north segment, and there is evidence that it was under WNW–ESE compression. The dextral strike‐slip faulting of the Ke‐Bai Fault is consistent with tectonic movement along the Kelameili, Sangequan, Wu‐Xia, Hong‐Che, and North Tianshan fault systems in the Junggar Basin. We therefore infer that counterclockwise rotation occurred in the Junggar Basin in the Jurassic. [ABSTRACT FROM AUTHOR]

The Northern Zhongtiaoshan Fault is a major deep fault at the southern margin of the Yuncheng Basin. There have been few studies on the fault, and the historical earthquakes are few and weak. However, the intensity of activity on the fault should never be underestimated. Through interpretations of aerial images, topography measurements and excavation of trenches, this paper studied the fault distribution, the surface deformation and the activity of the normal fault south of Salt Lake near the city of Yuncheng. By tracing faults in the three trenches, it was found that there had been at least three large paleoseismic events, at 1-3.5, 3.6-4.4 and 7.4-8.8 ka BP. Employing C dating, we determined the same gravel layers in the uplifted side and downthrown side. Making differential Global Positioning System measurements of the vertical difference and topographic profile, we obtained the mean slip rate of the Northern Zhongtiaoshan Fault since 24.7 ka BP (0.75±0.05 mm/a). Using the results of relevant studies, we calculated the possible vertical fault displacement of one earthquake (2.35 m) and obtained the recurrence interval of characteristic earthquakes as 2940-3360 a after dividing the displacement by the mean slip rate. [ABSTRACT FROM AUTHOR]

Tanlu fault (Liaozhong segment) goes straight through Liaodong Bay along NNE direction and it is divided into three segments, i.e., the northern segment, the middle segment and the southern segment, according to the differences in structural features. There are obvious changes in deposit thickness, sag structure, tectonic nature and other aspects of the layers. Tanlu fault is a special controlling factor concerning the reservoir formation in Liaozhong sag. First, its activities affect paleogeomorphology and paleogeographic framework and control the distribution of the sedimentary facies and then they proceed to control the distribution of the source rock and reservoir sand bodies. Second, its activities affect the formation and deformation of the structure, control the formation of abundant traps and cause the destruction of some traps. Third, its activities also affect the juxtaposition relation among the fault, the sand bodies and unconformity surfaces and control the function and efficacy of the three as the main hydrocarbon translocation system. In this paper the hydrocarbon reservoir formation process of JZ21-1, JX1-1 and LD27-2 oil and gas fields, the representatives of Tanlu strike slip fault zone are mainly analyzed. The modes of hydrocarbon reservoir formation can be generalized as follows-hydrocarbon source acts as 'soil' and oil and gas as 'nutrient'; hydrocarbon expulsion relies on 'roots'; hydrocarbon migration relies on 'trunks'; reservoir forms in 'brunches' and the whole process follows the pattern that 'hydrocarbon accumulates in strike slips and oil and gas reservoir forms like the growth of trees'. [ABSTRACT FROM AUTHOR]

Located at the intersection between a NW-trending slip system and NE-trending rift system in the northern South China Sea, the Qiongdongnan Basin provides key clues for us to understand the proposed extrusion of the Indochina Block along with Red River Fault Zone and extensional margins. In this paper we for the first time systematically reveal the striking structural differences between the western and eastern sector of the Qiongdongnan Basin. Influenced by the NW-trending slip faults, the western Qiongdongnan Basin developed E–W-trending faults, and was subsequently inverted at 30–21 Ma. The eastern sector was dominated by faults with NE orientation before 30 Ma, and thereafter with various orientations from NE, to EW and NW during the period 30–21 Ma; rifting display composite symmetric graben instead of the composite half graben or asymmetric graben in the west. The deep and thermal structures in turn are invoked to account for such deformation differences. The lithosphere of the eastern Qiongdongnan Basin is very hot and thinned because of mantle upwelling and heating, composite symmetric grabens formed and the faults varied with the basal plate boundary. However, the Southern and Northern Uplift area and middle of the central depression is located on normal lithosphere and formed half grabens or simple grabens. The lithosphere in the western sector is transitional from very hot to normal. Eventually, the Paleogene tectonic development of the Qiongdongnan Basin may be summarized into three stages with dominating influences, the retreat of the West Pacific subduction zone (44–36 Ma), slow Indochina block extrusion together with slab-pull of the Proto-South China Sea (36–30 Ma), rapid Indochina block extrusion together with the South China Sea seafloor spreading (30–21 Ma). [ABSTRACT FROM AUTHOR]

The confined groundwater in North China oilfield is contaminated by oil and oilfield gas. Based upon the analysis of the geological structures and hydrogeology of the study area, the pollution mechanism of the confined groundwater is studied. The main influencing factors are the oil-gas deposit size, the distribution of faults, oil exploitation well distribution, water input well distribution, aquifer media permeability, etc. The vulnerability assessment model is established for the confined groundwater in the study area, and the artificial neural networks (ANN) assessment method is adopted in this paper. The assessment results of the confined groundwater vulnerability fits well with the actual situations in the study area, which indicates the ANN assessment method is correct, accurate and objective. [ABSTRACT FROM AUTHOR]

SUMMARY This paper uses data from the Capital Area Seismograph Network in North China (NC), currently the largest regional seismograph network in China to investigate the compressional stress orientations from the polarizations of faster shear waves (PFS), a parameter of shear wave velocity anisotropy. Data are restricted to earthquakes deeper than 5 km to reduce the influence of the heterogeneous uppermost few kilometres of the crust. The results show that the regional compressional stress direction is ENE-WSW to nearly EW in NC, which agrees with seismic mechanisms and drilling and GPS data. Predominantly, PFS are also nearly EW in NC and are influenced by faults, geology and tectonics. PFS orientations at stations on seismically active faults are consistent with the strike of strike-slip faults and indicate large seismically active faults breaking, or nearly breaking, the free surface. PFS orientations are influenced by both regional compressional stress and by nearby faults. It is an effective way to study detailed spatial distribution of crustal compressional stress by shear wave anisotropy with dense seismograph network. Shear wave splitting may also be used to indicate hitherto unknown faults. [ABSTRACT FROM AUTHOR]

Composite borehole profiling combined with trenching is an effective way to acquire evidence of past ruptures of buried active faults. In this study, three composite borehole profiles and a large-scale trench excavation were carried out across the surface rupture zone of the 1976 M7.8 Tangshan earthquake. The following three major conclusions have been reached. (1) The surface rupture zone of the 1976 earthquake extends more than 47 km long to the south of Tangshan city, passing to the west of Sunjialou, to Daodi town in Fengnan County, to Xihe in Fengnan County. (2) The surface rupture zone is divided into south and north branches. The north branch has mainly right-lateral strike-slip motion, and the vertical displacement of the surface is up on the west and down on the east. On the other hand, the vertical displacement of the south branch is up on the east and down on the west, accompanied by some right-lateral slip. Such a faulting style cannot be explained by the movement of a single normal or reverse fault, but is consistent with the vertical displacement field induced by the right-lateral strike-slip of the fault belt. The drilling and trenching data from this study verify that such activity continued through the Late Quaternary on the Tangshan Fault. (3) The fault planes exhumed by trenching and the dislocations of strata revealed by the boreholes indicate that multiple faulting events occurred on the Tangshan Fault in the Late Quaternary. The timing of three ruptures prior to the 1976 earthquake was 7.61-8.13, >14.57, and 24.21-26.57 ka BP. Counting the earthquake of 1976, the recurrence interval of the four strong events is about 6.7 to 10.8 ka. On one of the three borehole profiles, the Niumaku profile, nine faulting events were detected since 75.18 ka BP with an average interval of 8.4 ka. In addition, this paper also discusses the difference between the Late Quaternary sedimentary environments to the north and south of Tangshan city based on stratum dating. [ABSTRACT FROM AUTHOR]

The N-S trending Xiaojiang fault zone and the NW-SE trending Qujiang-Shiping fault zone are adjacent active fault systems and seismogenic zones associated with strong and major earthquakes in Yunnan, China. To understand the interaction of the two fault systems, and its probable influence on earthquake occurrences, this paper conducts a synthetic study based on data of active tectonics, historical earthquakes, relocated small earthquakes, GPS station velocities and focal mechanism resolutions. The study makes several conclusions. (1) The active southward motion of the western side of the Xiaojiang fault zone (i.e. the side of the Sichuan-Yunnan block) has a persistent and intensive effect on the Qujiang-Shiping fault zone. The later fault zone has absorbed and transformed the southward motion of the western side of the former fault zone through dextral strike-slip/shearing as well as transverse shortening/thrusting. (2) Along the Xiaojiang fault zone, the present sinistral strike-slip/shearing rate decreases from 10 and 8 mm/a on the northern, central and central-southern segments to 4 mm/a on the southern segment. The decreased rate has been adjusted in the area along and surrounding the Qujiang-Shiping fault zone through reverse-dextral faulting and distributed shearing and shortening. (3) The tectonic-dynamic relation between the Xiaojiang fault zone and the Qujiang-Shiping fault zone is also manifested by a close correlation of earthquake occurrences on the two fault zones. From 1500 to 1850 a sequence of strong and major earthquakes occurred along the Xiaojiang fault zone and its northern neighbor, the Zemuhe fault zone, which was characterized by gradually accelerating strain release, gradually shortening intervals between M⩾7 events, and major releases occurring in the mid to later stages of the sequence. As a response to this sequence, after an 88-year delay, another sequence of 383 years (from 1588 to 1970) of strong and major earthquakes occurred on the Qujiang-Shiping fault zone, and had the same features in accelerating strain release and its temporal course. (4) Since there has been no M⩾7 event for 177 years on the Xiaojiang fault zone, the potential risk of a strong or major earthquake occurring on this fault zone in the future should be noticed and studied further. [ABSTRACT FROM AUTHOR]

The hanging wall effect is an important factor that impacts the characteristics of strong ground motions in near-fault areas. Based on a residual analysis of ground motion parameters characterizing the hanging wall effect and in recognition of the nature of the effect, many models have been developed. In this study, after a comprehensive analysis of two existing models, a new model is proposed and used to model the hanging wall effect in horizontal peak ground acceleration (PGAH) and spectral acceleration (SAH) at a period of 0.1 s in the Wenchuan earthquake. Finally, comparisons between the modeling results of the hanging wall effect in the Wenchuan earthquake and the results predicted by using Abrahamson and Silva's NGA model (AS NGA) indicate that the AS NGA model predicts a much higher hanging wall effect than the model developed in this paper. Furthermore, the AS NGA model predicts a large hanging wall effect even at great distances, while the proposed model more accurately captures the trend of the effect. [ABSTRACT FROM AUTHOR]

Tectonic activity offshore China during the Late Miocene and Quaternary ('neotectonism') generated unconformities, resulted in depocentre migration, created new faults and initiated earthquake activity. This episode of structural disturbance, which occurred during post-rift thermal subsidence, modified pre-existing hydrocarbon accumulations and formed new pools. Constructive effects of neotectonism occurred in the Bozhong Depression, Zhu #2 Depression and the Yinggehai Basin. These effects included the formation of new structural traps, migration routes and source kitchens. Destructive effects occurred in the Xihu Depression where oil/gas fields were partially breached by post-trap peneplanation and faulting. There are pools with active gas leakage through neotectonic faults and this seems to suggest a dynamic balance between outboard leakage of gas and inboard migration of hydrocarbons. This paper summarizes understanding of the past 15 years of offshore exploration in China which has primarily focused on Neogene reservoirs. Data used for this report include extensive coverage of conventional P-wave and multi-component 2D and 3D seismic data, drilling results and extensive geochemical and geological analyses. [ABSTRACT FROM AUTHOR]

This paper analyzes the seismicity in Bohai Sea, introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea, a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method, a scheme of two seismic design levels is proposed, and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings, it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000–2500 years, respectively. The validity of these proposed values is discussed. Finally, the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea. [ABSTRACT FROM AUTHOR]

Active faults in urban have a potential damage to citizens, because they can induce not only earthquakes, but also damage pavements, utilities, homes, businesses, factories and other manmade structures because of the slow, secular and differential slippage. Consequently, the researches of detecting active faults are of great significance. This paper proposes a set of geophysical methods to detect active faults by an example in Beijing, including gravity, controlled source audio-frequency magnetotellurics(CSAMT), seismic reflection, DC resistivity and paleomagnetism (Natural remanent magnetization in rocks) to locate faults and discuss their activities. In proposed methods, gravity interpretation helps us obtain the distribution and characteristics of buried faults beneath the plain, the results of CSAMT, seismic reflection and DC resistivity reveal features and characteristics of faults from the deep to shallow part; paleomagnetism associated with radiocarbon dating help us analyze the fault slip rate; 3D seismic reflection interpretation shows the structure of two faults in the three-dimensional subsurface and the interaction of each other. Also, a few acquisition parameters, data processing methods and significant suggestions are mentioned. [ABSTRACT FROM AUTHOR]

The Shirenzhang tungsten deposit is a classic wolframite-quartz vein-type deposit located in northern Guangdong Province, eastern segment of the Nanling W-Sn polymetallic belt. The ore veins, controlled by the NW-striking fault system, are mainly hosted in the Ordovician metasedimentary rocks and can also be found with less amount in the cupola of the concealed granitic stock, displaying a typical five-floor vertical zonation proposed by the Chinese geologists. The concealed granitic stock mainly comprises two intrusive facies, the porphyritic biotite granite (G1) in the outer zone and the medium- to fine-grained monzogranite (G2) in the inner zone. In this paper, we report new cassiterite U-Pb ages and Pb isotopes of sulfides for the Shirenzhang tungsten deposit, combined with new zircon U-Pb ages and Hf isotopes, elemental geochemistry and Sr-Nd-Pb isotopes of the concealed granitic rocks, with aims to elucidate the origin of the ore-related granites and the link between the tungsten mineralization and granitic magmatism. LA-ICP-MS zircon U-Pb dating gives the weighted mean ages of 164 ± 2 Ma for G1 and 162 ± 4 Ma for G2, respectively. Cassiterite from the wolframite-bearing quartz vein and the drusy quartz vein yield the weighted mean ages of 164 ± 2 Ma and 160 ± 2 Ma, respectively. These ages suggest that both the granitic intrusion and related W-(Sn) mineralization in the Shirenzhang deposit were initiated during the late Jurassic (ca. 160 Ma). The Shirenzhang granitic rocks are weakly peraluminous highly fractionated I-type granites. Detailed elemental and isotopic data demonstrate that the granitic rocks were derived from partial melting of the Paleoproterozoic basement rocks at a relatively shallow depth of ~30 km triggered by underplating of basaltic magma, and underwent extensive fractional crystallization of hornblende, biotite, feldspar, and monazite and/or allanite. A continental arc setting induced by northwesterly subduction of the paleo-Pacific plate is suggested for the genesis of the Shirenzhang I-type granites. The comparable Pb isotopic compositions of feldspar and sulfides imply that the lead in the ore veins was of magmatic origin. Integrating the spatial-temporal relationship between the ore veins and the concealed granitic rocks with the Pb isotopes from the sulfides and granites, we suggest that the tungsten mineralization is genetically linked with the concealed granitic rocks in the Shirenzhang deposit. Fractional crystallization and melt-fluid interaction may play an important role on the formation of the granite-related tungsten mineralization. [ABSTRACT FROM AUTHOR]

The Longyao ground fissure (LGF) is the longest and most active among more than 1000 ground fissures on the North China Plain. There have been many studies on the formation mechanism of the LGF, due to its scientific importance and its potential for damage to the environment. These studies have been based on both regional tectonic analysis and numerical simulations. In order to provide a better understanding of the formation mechanism, the deformation of the crack and its surrounding environment should be taken into consideration. In this paper, PS-InSAR technology was employed to assess the ground deformation of LGF and its surrounding area, using L-band ALOS-1 PALSAR images from 2007 to 2011. The characteristics of ground deformation, relationships between fissure activity and surrounding faults and groundwater exploitation were analyzed. This study shows that the north side of Longyao fault (LF) is uplifting while the south side is subsiding. This provides the tectonic conditions responsible for the activity of the ground fissure. Local groundwater exploitation also plays an important role in the development of ground fissures. InSAR observations were modeled to infer the loading depth (-2.8 km) and the slip rate (31.1 mm/yr) of LF. [ABSTRACT FROM AUTHOR]

This paper presents a case history of geological hazards and treatment measures during the shield tunneling of Metro Line No. 7, in water-rich mylonitic faults in Guangzhou, China. The site selection of Metro Line No. 7 is introduced based on the land use and the geology in Guangzhou. Metro Line No. 7 passes through a number of dead faults, which are unavoidable due to the presence of urban residences and geological formations. The mylonitic rock faults feature rock fractures, high rock permeability, complex formation structure, susceptibility to collapse, and rich groundwater. Geohazards during tunneling in groundwater-rich mylonitic faults include ground collapse, groundwater in-flows, land subsidence, and long-term instability of tunnel. These types of hazards would delay the construction of tunnels and potentially cause significant damage to the tunnels. Preventions and treatments for these hazards aforementioned are analyzed based on the tail grouting material optimization, advanced ground monitor, grouting treatment and shield machine modification, with monitoring the feedback data. The mechanism of ground collapse is discussed according to the cavity expansion principle. [ABSTRACT FROM AUTHOR]

The Fodongmo-Hongyazi fault (FHF) is a major thrust of Northeastern Tibet, bounding the Qilian Shan. It accommodates crustal shortening across this region and has produced a strong historical earthquake. Until now the slip rate has been poorly constrained, limiting our understanding of its role in the accommodation of deformation across this region. In this paper, faulted terraces at two sites on the western and middle segments of the FHF were mapped with satellite imagery and field observations. Chronological constraints are placed on the ages of displaced river terraces at these sites using terrestrial cosmogenic nuclide (TCN) exposure dating. These ages combined with offsets measured from SPOT 6 DEM’s yield average vertical slip rates of 1.3 ± 0.1 mm/yr for the western segment since ∼207 ka and 0.9 ± 0.1 mm/yr since ∼46 ka for the middle segment. These data suggest that the FHF accommodates ∼15–20% of the total shortening across the Qilian Shan (5.5–7 mm/yr). In addition, comparisons of our data with published slip rates along the Northern Qilian Thrust Fault Zone show that the fastest tectonic uplift occurs along the western portion of the Northern Qilian Shan. This is consistent with estimates deduced from geomorphology. The western portion of the Qilian Shan is mainly controlled by compressional deformation produced by the northward movement of the Northeastern Tibetan Plateau, while the eastern Qilian Shan is mainly controlled by the eastward extrusion of material along the left-lateral Haiyuan strike-slip Fault. [ABSTRACT FROM AUTHOR]

The vertical slip rate of a normal fault is one of the most important parameters for evaluating its level of activity. The Sertengshan piedmont fault has been studied since the 1980s, but its absolute vertical slip rate has not been determined. In this paper, we calculate the displacements of the fault by measuring the heights of piedmont terraces on the footwall and the stratigraphic depths of marker strata in the hanging wall. We then calculate the vertical slip rate of the fault based on the displacements and ages of the marker strata. We selected nine sites uniformly along the fault to study the vertical slip rates of the fault. The results show that the elevations of terraces T3 and T1 are approximately 1060 m and 1043 m, respectively. The geological boreholes in the basin adjacent to the nine study sites reveal that the elevation of the bottom of the Holocene series is between 1017 and 1035 m and that the elevation of the top of the lacustrine strata is between 925 and 1009 m. The data from the terraces and boreholes also show that the top of the lacustrine strata is approximately 65 ka old. The vertical slip rates are calculated at 0.74–1.81 mm/a since 65 ka and 0.86–2.28 mm/a since the Holocene. The slip rate is the highest along the Wujiahe segment and is lower to the west and east. Based on the findings of a previous study on the fault system along the northern margin of the Hetao graben basin, the vertical slip rates of the Daqingshan and Langshan faults are higher than those of the Sertengshan and Wulashan faults, and the strike-slip rates of these four northern Hetao graben basin faults are low. These results agree with the vertical slip components of the principal stress field on the faults. The results of our analysis indicate that the Langshankou, Wujiahe, and Wubulangkou areas and the eastern end of the Sertengshan fault are at high risk of experiencing earthquakes in the future. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M~8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models (DEMs), in combination with field survey, demonstrate that: (i) the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches; (ii) the landslides are mostly developed upon steep slopes of ≥30°; and (iii) the step-like normalfault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting. [ABSTRACT FROM AUTHOR]

Abundant geothermal springs occur along the Moxi fault located in western Sichuan Province (the eastern edge of the Qinghai-Tibet plateau), highlighted by geothermal water outflow with an unusually high temperature of 218 °C at 21.5 MPa from a 2010-m borehole in Laoyulin, Kangding. Earthquake activity occurs relatively more frequently in the region and is considered to be related to the strong hydrothermal activity. Geothermal waters hosted by a deep fault may provide evidence regarding the deep underground; their aqueous chemistry and isotopic information can indicate the mechanism of thermal springs. Cyclical variations of geothermal water outflows are thought to work under the effect of solid earth tides and can contribute to understanding conditions and processes in underground geo-environments. This paper studies the origin and variations of the geothermal spring group controlled by the Moxi fault and discusses conditions in the deep ground. Flow variation monitoring of a series of parameters was performed to study the geothermal responses to solid tides. Geothermal reservoir temperatures are evaluated with Na-K-Mg data. The abundant sulfite content, dissolved oxygen (DO) and oxidation-reduction potential (ORP) data are discussed to study the oxidation-reduction states. Strontium isotopes are used to trace the water source. The results demonstrate that geothermal water could flow quickly through the Moxi fault the depth of the geothermal reservoir influences the thermal reservoir temperature, where supercritical hot water is mixed with circulating groundwater and can reach 380 °C. To the southward along the fault, the circulation of geothermal waters becomes shallower, and the waters may have reacted with metamorphic rock to some extent. Our results provide a conceptual deep heat source model for geothermal flow and the reservoir characteristics of the Moxi fault and indicate that the faulting may well connect the deep heat source to shallower depths. The approach of hot spring variation research also has potential benefits for earthquake monitoring and prediction. [ABSTRACT FROM AUTHOR]

We established a three-dimensional finite element model of the Anninghe-Zemuhe-Xiaojiang faults region using contact surfaces of different sizes to describe the spatial segmentation characteristics of the faults. Our model is based on constraints from GPS observations, models of the crust and upper mantle, precise earthquake locations, the tectonic stress field, the slip rate of the faults, and the rheology of the lithosphere in the Sichuan-Yunnan area. Considering the influence of strong earthquakes since A.D. 1327, we analyzed the main controlling factors of the characteristics of the strong earthquakes and also studied by numerical simulation the possible areas of future earthquake risk and their relationship with tectonic stress. The numerical results showed that the gravitational potential energy of the Qinghai-Tibet Plateau and the interaction of adjacent blocks are the main kinetic factors affecting the characteristics of the tectonic stress distribution. There appears to be some correspondence between the distribution of tectonic stress and the b value; however, we also found that some low b value locations correspond to regions of lower stress. This contradiction may be the result of some comprehensive factors, such as the release of strain energy caused by strong earthquakes. [ABSTRACT FROM AUTHOR]

Fault-sealing capability has critical influence on coalbed methane (CBM) accumulation and preservation in coal-bearing basins. Although southern Qinshui Basin is the first commercial CBM production area in China, detailed investigation on faults evolution and its impact on gas accumulation has never been performed. In this paper, the generation time and the evolution process of the sealing capability of seven major faults in the Zhengzhuang field were evaluated by using well-logging data and 3D seismic tectonic interpretation. Results indicate that most normal faults in the Zhengzhuang field were created from Late Cretaceous to Paleogene and after the key stage of hydrocarbon-generation. Fault-sealing capability was evaluated through the vertical pressure on the faults' surface ( VPFS ), the shale gouge ratio ( SGR ) and the clay-smear potential ( CSP ), the values of which for Zhengzhuang field are −3.2 MPa to 16 MPa, 0.36 to 0.91, and 2–40 m, respectively. These values demonstrate that the fault-sealing is complex and variable when the faults present in different scales or different positions in the faulting system. In the Zhengzhuang field, almost all faults exhibit good lateral sealing capability ( LSC ) with high values of SGR (>0.6) and CSP (>15 m) during fault evolution. Therefore, the current gas contents are primarily related to the vertical sealing capability ( VSC) but not to the LSC of the faults. The VSC of the fault varies with the different stages during the fault evolution. In the Late Cretaceous-Paleogene, a key stage for gas dissipation, almost all faults possess low VSC, which caused generally low gas content (<22.4 m 3 /t) near the faults. In contrast, the gas content that was not affected by faults is commonly >25 m 3 /t. In the Neogene-Quaternary, the VSC was variable for different faults. For the faults with low VSC, they would gradually lead to low gas content. The results showed that the VSC positively correlated with the current gas contents near the faults in the Zhengzhuang field, southern Qinshui Basin, North China. [ABSTRACT FROM AUTHOR]

Two active faults, including the Huashan piedmont fault (HPF) along the northern margin of Huashan Mountain and the north margin fault of the Weinan loess tableland (NMF-WLT), were developed in the southeastern Weihe Graben, in central China. HPF, which is the most active fault in the Weihe Graben, is known throughout the world for the M8 1 / 4 great Guanzhong earthquake in 1556 AD. Through field investigation, AMS 14 C, and OSL dating in this paper, in combination with previous studies, the following results are obtained: (i) Tectonic landforms, such as triangular fault facets, waterfalls and fault scraps of proluvial fans, were developed in the HPF, but these features were not developed in the NMF-WLT. (ii) HPF experienced three intensive seismic activities in 5920–7670 Cal yr BP, 2215 ± 95–3105 ± 105 Cal yr BP and 1556 AD during the Holocene, but there has only been one seismic event noted for the NMF-WLT since the Holocene (6865 ± 80 Cal yr BP). (iii) The dip-slip rate of the HPF was approximately 0.64 mm/yr since the mid-Pleistocene and approximately 1.67–2.71 mm/yr in the Holocene. In contrast, the dip-slip rate of NMF-WLT was approximately 0.32–0.42 mm/yr since the early Pleistocene and was approximately 0.39–0.58 mm/yr from the late Pleistocene to the Holocene. (iv) The seismic activity at the HPF has been more intense than at the NMF-WLT; the HPF was the triggering seismic fault of the M8 1 / 4 great Guanzhong earthquake in 1556 AD, whereas the NMF-WLT was not the seismogenic fault of this event. These results provide new information for the study of active tectonics of the Weihe Graben. [ABSTRACT FROM AUTHOR]

The relation between magmatic activity and detachment faulting during continental lithospheric extension remains a persistent question. This paper takes the Liaonan metamorphic core complex (mcc) in the eastern North China craton as an example to explore how magma generation relates to detachment faulting in response to continental lithospheric extension due to the subduction of the Paleopacific plate beneath the Eurasian continent in the Early Cretaceous. Dating of lower plate granitic intrusions and trachy-dacitic volcanic rocks in the supradetachment basin constrains a progressive exhumation of the mcc between ca. 134 Ma and 113 Ma. Syn-tectonic magmatism is grouped into three types, i.e., early syn-kinematic, late syn-kinematic, and post-kinematic magmatism, in reference to detachment faulting. The magmatic rocks exhibit obvious differences in whole-rock Sr–Nd isotopes, implying varying sources, e.g., lithospheric mantle, juvenile and ancient lower crusts. Evolving magma sources during the progressive exhumation of the mcc are shown from one with a lithospheric mantle signature for the early syn-kinematic intrusions to one with mixed derivations from both juvenile and ancient lower crust for the late syn-kinematic plutons and volcanics and, finally, to a juvenile lower crust source for the post-kinematic intrusions. The source evolution of magmatism during the continental lithospheric extension implies that both crustal and mantle processes may have been involved in the magma generation. The Parallel Extension Tectonics model is applied to explain both the tectonic faulting and magmatic activities. In the model, the evolving magma sources accompanying the mcc exhumation were attributed to thinning of the cratonic lithosphere as a consequence of coupled crust–mantle detachment faulting during tectonic extension. The model can be applied to the variably extended provinces in the North China craton, but integrated structural, geochronological and geochemical studies are needed to present a comprehensive tectono-thermal (magmatic) history of these provinces. [ABSTRACT FROM AUTHOR]

The Pliocene fluvial/lacustrine sediments of the Sanying Formation lie along the Red River fault and its northwest extension; their majority outcrops appear around Eryuan. The Sanying Formation is characterized by multiple intercalated coal layers and its unconformities contact with the underlying Triassic limestone and the overlying Quaternary coarse sediments. Cosmogenic nuclide burial dating confirms the Pliocene age of the Sanying Formation. The burial ages of the overlying Quaternary sediments provide the lower age limit of the Sanying Formation: 2 Ma. Detrital zircon U-Pb age distribution suggests provenance of the Sanying Formation traced to the Songpan-Ganzi flysch belt. From the spatial distribution as well as sedimentary and fault ages, we found a strong connection of the Sanying Formation with the Red River and the Jianchuan faults. We therefore propose that activation of the Red River and the Jianchuan faults during the Late Miocene resulted in subsidence of basins in the extensional areas around Eryuan and in the middle to south segments of the Red River fault. The basins were filled with water carried by the Jinsha River and overflow-lakes formed within the basins where the Sanying Formation was deposited. Most of the lakes were dried and sedimentation of the Sanying Formation ceased due to the uplift of the Yunling Mountains, which forced rerouting of the Jinsha River at the beginning of Quaternary. [ABSTRACT FROM AUTHOR]

Abstract: One of various mechanisms of pre-earthquake lithosphere–atmosphere–ionosphere coupling as possible explanation of the seismo-ionospheric effects is connected with the release of latent heat. Abnormal variations of ionospheric electromagnetic parameters possibly related to the 2007 Ms 6.4 Pu’er earthquake in China were reported. This paper attempts to examine whether there were abnormal changes of surface latent heat flux (SLHF) linked with this pre-earthquake ionospheric disturbances. The spatio-temporal statistical analyzes of multi-years SLHF data from USA NCEP/NCAR Reanalysis Project reveal that local SLHF enhancements appeared 11, 10 and 7days before the Pu’er earthquake, respectively. As contrasted to the formerly reported local ionospheric Ne enhancement 9days before the shock observed by DEMETER satellite, it is discovered that the SLHF and Ne anomalies are quasi-synchronous and have good spatial correspondence with the epicentre and the local active faults. This is valuable for understanding the seismogenic coupling processes and for recognizing earthquake anomaly with multiple parameters from integrated Earth observation system. [Copyright &y& Elsevier]

Abstract: The Longmen-Shan fault zone, at the eastern margin of the Tibetan Plateau, is one of the most extensively studied areas in the world, yet the deformation model and earthquake-generating mechanism remain subjects of vigorous debate. This paper presents a new three-dimensional (3-D) velocity model determined using a large volume of seismic data and two-dimensional (2-D) magnetotelluric (MT) profiles from previous studies, to investigate the mechanisms of crustal deformation and earthquake generation along the reverse-thrust and strike-slip fault zone. It has been observed that low-velocity, and low-resistivity anomalies related to the Sichuan foreland basin, is in sharp contrast to high-velocity and high-resistivity anomalies in the Songpan-Ganze block in the upper crust. The tomographic model presented here reveals two crustal bodies with low-velocity and high-conductivity anomalies underneath the Longmen-Shan fault zone, separated into three contrasting segments by the two crustal bodies. The two low-velocity and low-resistivity bodies have been interpreted as being associated with extrusion of either fluids or products of partial melting from the lower crust and/or the upper mantle. This suggests strong variations in the rheological strength of the rock along the fault zone. This finding implies that coupling between these presumably fluid-bearing bodies and earthquake generation could be extremely complex and that there is dramatic variation from the southwestern area to the northeastern segment along the fault belt. It is suggested here that this complex and variable deformation system along the fault zone played a principal role in controlling seismic generation and rupturing during the 2008 Wenchuan earthquake (Ms 8.0) and that it will do so again during possible future earthquakes in the region. [Copyright &y& Elsevier]

A 1-D unloaded tectonic subsidence (air-loaded tectonic subsidence) model is proposed and applied to the Qiongdongnan Basin. Results show that three episodes of subsidence exist in Cenozoic, that is, syn-rift rapid subsidence (Eocene–Oligocene) with subsidence rate at 20–100 m/m.y., post-rift slow thermal subsidence (early-middle Miocene) around 40 m/m.y., and post-rift accelerated subsidence (since late Miocene) 40–140 m/m.y., which is substantially deviated from the exponentially decayed thermal subsidence model. For exploring the mechanism of post-rift accelerated subsidence, the faulting analyses are conducted and results show that there is a dramatically decrease in the numbers of active faults and fault growth rate since 21 Ma, which indicates that no active brittle crust extension occurred during post-rift period. Furthermore, previous studies have demonstrated that the stretching of the upper crust is far less than that affecting the whole crust. Therefore, we infer that the lower crust thinned during the post-rift period and a new model of basin development and evolution is put forward to explain the post-rift accelerated subsidence and depth-dependent crust thinning in the Qiongdongnan Basin, which is supported by gravity data. [ABSTRACT FROM AUTHOR]

Oil and gas exploration near faults in shallow strata is investigated in this study based on an analysis of oil-source faults in reservoirecap rock combinations without a source rock. The oil-source faults were mapped by superimposition of the distribution area of oil-source faults and the leakage area of cap rocks. This method is applied to the mapping of oil-source faults for two sets of reservoirecap rock combinations without a source rock in the Banqiao area of the Qikou Sag in the Bohai Bay Basin, eastern China. Combination B is formed by a mudstone cap rock of the middle sub-member of the 1st member of the Shahejie Formation (E3s1 M) with its underlying reservoir, while Combination C is formed by a mudstone cap rock of the 2nd member of the Dongying Formation (E3d2) with its underlying reservoir. The results show that the oil-source faults of Combination B are relatively better developed and mainly occur in the northeast and southeast, while those of Combination C are not as well developed and are only distributed at the southeastern edge of the study area with a small proportion in the north. These results are consistent with the fact that oil and gas are mainly distributed near oil-source faults, proving the method proposed is workable in determining the oil-source faults in reservoirecap rock combinations without a source rock. [ABSTRACT FROM AUTHOR]

Seismic anisotropy can be linked to different mechanisms, structures, and sources. We constrained the 3‐D depth‐dependent shear wave speed isotropic and azimuthally anisotropic structures with Rayleigh wave phase velocity from ambient noise in central Eastern China. We compared the results with other models and found that in the upper crust, the maximum horizontal stress direction differs mainly from the anisotropy that coincides with the strikes of major faults and geologic structures. We inferred that the anisotropy within proximity of faults might be related to fault fabrics, including fractures that strike parallel to the fast axes. The Tan‐Lu Fault controls the anisotropy in the crust to the uppermost mantle. The direction of fast axes in the fault zone is NNE‐SSW to N‐S, coinciding with the fault strike and trend that matches the fault shape on the surface. Southeastern North China craton has a weak anisotropy in the crust and uppermost mantle. The sources are possibly connected to the thrusting, tight trending folds, and dipping thrusts observed to be sub‐parallel to the Dabie Orogenic Belt (DOB). We propose that the NNE‐SSW Zhangbaling uplift group comes from the extension and ductile shearing in the Tan‐Lu Fault zone and the dragging of the northeastern South China Craton in the crust and the uppermost mantle. The N‐S polarized fast axes in the lower crust and uppermost mantle across the Sulu orogen and Xuzhou thrust‐and‐fold belt are the products of the resultant effect of subduction and deep Tan‐Lu faulting. Plain Language Summary: Seismic anisotropy is the dependence of seismic velocity of the medium on wave propagation direction. When observed, it gives information about the nature of material deformation. We used surface waves recovered from background noise to determine the anisotropy and its connection to the Tan‐Lu fault system, the largest fault system in Eastern China. Our results show that seismic anisotropy in the upper crust is likely caused by fault zone fabrics and the regional stress field. In the middle crust to the uppermost mantle, the anisotropy is parallel to the strike of the Tan‐Lu fault, indicating that the fault penetrates to the uppermost mantle and controls the anisotropy. The southeastern North China craton has weak anisotropy in the crust and uppermost mantle. The cause of anisotropy is likely the thrust faults resulting from compression that strike similar to the trend of the Dabie Orogenic Belt. The extension and shearing in the Tan‐Lu Fault zone is likely what caused the anisotropy at Zhangbaling uplift. The direction of anisotropy changes to N‐S in the north of the study region in the lower crust and uppermost mantle. The cause might be related to the resultant effect of subduction and deep Tan‐Lu faulting. Key Points: Azimuthal anisotropy in the crust and uppermost mantle deviates from stress, shear‐wave splitting, and absolute plate motion directionWithin proximity of regional faults, anisotropy might be related to fault fabrics including fractures that strike parallel to the fast axesThe direction of anisotropy coincides with the strike of the Tan‐Lu Fault signifying structural sources in the crust and uppermost mantle [ABSTRACT FROM AUTHOR]

Abstract: Scientific drilling in active faults after a large earthquake is ideal to study earthquake mechanisms. The Wenchuan earthquake Fault Scientific Drilling project (WFSD) is an extremely rapid response to the 2008 Ms 8.0 Wenchuan earthquake, which happened along the Longmenshan fault, eastern margin of the Tibetan Plateau. In order to better understand the fault mechanism and the physical and chemical characteristics of the rocks, the WFSD project will eventually drill 5 boreholes along the two main faults. This paper focuses on the first hole (WFSD-1), which started just 178days after the earthquake, down to a final depth of 1201.15m. Petrological and structural analyses of the cores allowed the identification of fault-related rocks in the Yingxiu–Beichuan fault (fault gouge, cataclasite, and fault breccia), and the Principle Slip Zone (PSZ) location of the Wenchuan earthquake was determined. We found 12 fault zones in the entire core profile, with at least 10, including the Yingxiu–Beichuan fault zone, with a multiple cores structure and minimum width of ~100m. The co-seismic slip plane of the Wenchuan earthquake at depth (corresponding to the Yingxiu–Beichuan fault zone at the outcrop), as well as its PSZ, was expected to be located at the bottom of the fault zone (at 759m-depth). Instead, it was found at ~590m-depth with 1cm-wide fresh fault gouge, as determined by logging data such as temperature, natural gamma ray, p-wave velocity and resistivity, combined with the fresh appearance, magnetic susceptibility, and microstructure of the gouge. The Wenchuan earthquake slip plane has a dip angle of ~65°, showing the high-angle thrust feature. The distribution of fault gouge with several meters thick, the location of the Wenchuan earthquake''s PSZ and the thickness of fresh gouge all imply a correlation between the width of the fault zone and the number of seismic events. [Copyright &y& Elsevier]

Abstract: Pre-existing faults or early formed faults may be reactivated or locked in subsequent evolution in a rift basin. The reactivation or sealing of a fault affects sedimentation in the related fault block, and in turn controls the accumulation of oil and gas. Based on fault mechanics of reactivation, this paper established equations denoting the angle range of the reactivated faults or frictional sliding faults by using Mohr stress circles. The results were applied to explain the sealing property of pre-existing faults or early formed faults in Dongpu sag. In the Dongpu sag, reactivation or sealing of the faults in fault blocks is supposed due to the rotation of the fault block which was caused by the activity of high order faults. For quantitative calculation of dip range for activated faults, the sum of the maximum and minimum principal stresses were determined by acoustic emission experiment based on the Kaiser effect of rocks, and the cohesion and inner frictional angle of rocks were measured by rock physical experiment. The calculations show, when the dips of early formed faults are from 87° to 45°, the faults will remain activation in the subsequent deformation. Otherwise, the faults will be locked as sealing faults. The results of petroleum exploration show that the peak dips of sealing faults are from 36° to 40°, and the most of sealing faults are those with dip angles less than 46–50°. These results indicate that a shallower fault is of better sealing property in oil and gas reservoirs than a steeper fault in Dongpu sag. [Copyright &y& Elsevier]

Abstract: The 2008 Ms 8.0 Wenchuan earthquake of China ruptured two large faults along the Beichuan-Yingxiu thrust belt and the Pengguan thrust belt at the Longmen Shan Orogenic belt, eastern margin of the Tibetan Plateau. Our study focused on the structural geometry at the Pengguan thrust belt located at the frontal zone of the Central Longmen Shan. In this paper, in order to identify the co-seismic fault at the Pengguan thrust belt many 2-D/3-D seismic reflection profiles have been interpreted by integrating with the geological maps, drilling data, DEM data and the surface ruptures. The results show that there were three major faults and other branch faults at the Pengguan thrust belt. The major faults have formed as imbricates and associated minor duplexes within the shallow strata. The Pengguan fault has a steep dip at the shallow surface and a gentle dip at depth. Both the Beichuan-Yingxiu fault and the Pengguan fault were developed on the shallow detachment in the central segment of Longmen Shan. The third (No. ③) Pengguan fault is coincident with the co-seismic surface ruptures. It was a pre-existing fault and re-activated during the Wenchuan earthquake. Three-dimensional geometries show that the No. ③ fault is heterogeneous and it has controlled the slip of co-seismic ruptures. Based on the regional geology, the 3-D fault geometry and the surface ruptures, the frontal zone of the Central Longmen Shan has been divided into the Bailu segment and the Hanwang segment. Our studies suggest that the Pengguan fault has been active since the Cenozoic. The frontal zone of the Central Longmen Shan thrust belt has potential for future earthquakes. [Copyright &y& Elsevier]

Abstract: The large oblique reverse slip shock of the 2008 Mw=7.9 Wenchuan earthquake, China, produced one of the longest and most complicated surface ruptures ever known. The complexity is particularly evident in the Xiaoyudong area, where three special phenomena occurred: the 7km long Xiaoyudong rupture perpendicular to the Beichuan-Yingxiu fault; the occurrence of two parallel faults rupturing simultaneously, and apparent discontinuity of the Beichuan-Yingxiu rupture. This paper systematically documents these co-seismic rupture phenomena for the Xiaoyudong area. The discussion and results are based on field investigations and analyses of faulting mechanisms and prevalent stress conditions. The results show that the Beichuan-Yingxiu fault formed a 3.5km wide restraining stepover at the Xiaoyudong area. The Xiaoyudong fault is not a tear fault suggested by previous researches, but a frontal reverse fault induced by the oblique compression at this stepover; it well accommodates the ‘deformation gap’ of the Beichuan-Yingxiu fault in the Xiaoyudong area. Further, stress along the Peng-Guan fault plane doubles due to a change in dip angle of the Beichuan-Yingxiu fault across the Xiaoyudong restraining stepover. This resulted in two faults rupturing the ground’s surface simultaneously, to the north of the Xiaoyudong area. These results are helpful in deepening our understanding of the dynamic processes that produced surface ruptures during the Wenchuan earthquake. Furthermore, the results suggest more attention be focused on the influence of dextral slip component, the change of the control fault’s attitude, and property differences in rocks on either side of faults when discussing the formation mechanism of surface ruptures. [Copyright &y& Elsevier]

Abstract: The history of basin formation and crustal deformation of the Korean Peninsula is here critically reviewed to show it is an important tectonic architecture of the collision between North and South China in Early Mesozoic. To synthesize our current geologic and paleomagnetic knowledge, we propose a new crustal detachment and extrusion model for the continental collision and rotation between the North and South China Blocks (NCB and SCB) east of the Tancheng–Lujiang fault. We emphasize that the Yellow Sea Transform Fault (YSTF) played a key role in accommodating the collisional history of the two blocks in the east end. The YSTF allowed the Korean Peninsula exempted from being directly involved in the NCB–SCB collision. During the Early Triassic collision phase of the two blocks, a large piece of the upper crust of the northeastern part of the SCB was detached and slumped over the Korean Peninsula and fragmentally deposited in the metamorphosed Okcheon Trough. In the course of the exhumation of the Sulu ultra-high-pressure (UHP) metamorphic belt in the Middle Triassic, the northern part of the SCB extruded eastward toward Korea. A general time correlation of the Songnim orogeny of Korea and the early exhumation of the Sulu UHP metamorphic belt suggests their genetic relation. The exhumation of the Sulu UHP metamorphic belt triggered the mid Triassic extrusion tectonics, which in turn facilitated the clockwise rotation of the SCB. The eastward extrusion and clockwise rotation of the SCB (relative to NCB) exerted a large amount of eastward compression to the Korean Peninsula and led to the Middle–Late Triassic Songnim orogeny. Geologic and paleomagnetic information synthesized in this paper has revived and reinforced the belief for the single Sino-Korean Craton which comprises Korea and north China since the Precambrian time. [Copyright &y& Elsevier]

Abstract: This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints). The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°), and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic. [Copyright &y& Elsevier]

Abstract: The Xianshuihe–Xiaojiang fault zone (XFZ) forms a prominent linear NW–SE trending tectonic feature along the southeastern margin of the Tibetan Plateau. The spatial and temporal evolution of the predominantly strike–slip movement along the fault remains unclear, as estimates for the initiation age of its different segments range from 5 to 13Ma. The Jinhe–Qinghe fault (JqF; the south part of the Longmen Shan thrust belt) provides a key for understanding the tectonic role and deformation history of the Xianshuihe–Xiaojiang fault zone in terms of timing, magnitude of displacement, and spatial–temporal evolution. This paper presents research on the structure and chronology of the JqF. The results of a geometric and kinematic study of the Jinhe–Qinghe fault show it to be a thrust fault with a left-lateral strike slip component; The strike slip offset extends at least 13–18km to southwest, based on the shortening of its folds and faulting, and based on stream deflection. Ten apatite fission track apparent ages show a pronounced change in age/elevation gradient at ~17±2Ma, consistent with an abrupt increase of exhumation due to uplift of the hanging wall of the JqF at that time. Combined with the age of deformed Tertiary strata in the footwall of the JqF and the geometric relationships of the JqF with the Chenghai fault and the XFZ, this indicates that the JqF was active between 17 and 5Ma. Based on the fault chronology, geometry, and movement, we suggest that the fault was a transpressional structure at the south end of the XFZ during the period from 17 to 5Ma. [Copyright &y& Elsevier]

Abstract: At the regional collapse of geological hazard evaluation process, in the selection of evaluation factors and determination of the weight, there are subjectivity, uncertainty, and many other issues. In this paper, the Haiyuan fault belt in Ningxia Province is the study area, respectively, with D-S evidence theory and fuzzy comprehensive evaluation methods to build a collapse of geological hazard assessment model, presented Concrete evidence theoretical algorithm. The application results show that the evidence theoretical evaluation model compared to fuzzy comprehensive evaluation model is more reliable and accurate. It solved the uncertainty evaluation issues. [Copyright &y& Elsevier]

Abstract: Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet Plateau. However, controversy still exists regarding the modes and mechanisms of the Tibetan Plateau uplift. Geology has recorded this uplift well in the Qaidam Basin. This paper analyzes the tectonic and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data. The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based on the tectonic developments, faults growth index, sedimentary facies variations, and the migration of the depositional depressions. The changes in the sedimentary facies show that lakes in the western Qaidam Basin had gone from inflow to still water deposition to withdrawal. Tectonic movements controlled deposition in various depressions, and the depressions gradually shifted southeastward. In addition, the morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic movements controlled the evolution of the Basin and divided it into (a) the southern fault terrace zone, (b) a central Yingxiongling orogenic belt, and (c) the northern fold-thrust belt; divided by the XI fault (Youshi fault) and Youbei fault, respectively. The field data indicate that the western Qaidam Basin formed in a Cenozoic compressive tectonic environment caused by the India–Asia plate collision. Further, the Basin experienced two phases of intensive tectonic deformation. The first phase occurred during the Middle Eocene–Early Miocene (Xia Ganchaigou Fm. and Shang Ganchaigou Fm., 43.8–22Ma), and peaked in the Early Oligocene (Upper Xia Ganchaigou Fm., 31.5Ma). The second phase occurred between the Middle Miocene and the Present (Shang Youshashan Fm. and Qigequan Fm., 14.9–0Ma), and was stronger than the first phase. The tectonic–sedimentary evolution and the orientation of surface structures in the western Qaidam Basin resulted from the Tibetan Plateau uplift, and recorded the periodic northward growth of the Plateau. Recognizing this early tectonic–sedimentary evolution supports the previous conclusion that northern Tibet responded to the collision between India and Asia shortly after its initiation. However, the current results reveal that northern Tibet also experienced another phase of uplift during the late Neogene. The effects of these two stages of tectonic activity combined to produce the current Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: China''s Lop Nur is one of the world''s largest playas, and is located in the driest part of Central Asia. Scientific explorations by Chinese and foreign researchers have been continuously conducted there since the mid- to late 1800s, and much progress has been made, but many issues remain hotly debated. Particularly intense debate focuses on the formation, environmental evolution, drying date of the Lop Nur lake, and cause of the helical salt crusts recently revealed by remote-sensing images. In this paper, we review the status of this research to provide insights that can inform studies in other arid zones that resemble the Lop Nur. The Lop Nur depression is a secondary unit of the Tarim Block, controlled by faults and fractures formed by the Himalayan orogeny, but various competing explanations have been proposed for how these geological structures gave rise to the depression. The depression''s formation date also remains unclear. Several boreholes have been created to reconstruct the environmental evolution at different time scales since the Quaternary, and deposition rates of lake sediments, especially since the Late Pleistocene, have averaged less than 1mm annually. The drying date of the Lop Nur lake is also debated. The helical salt crust structures appear to have formed as the lake shrank, but how and when they formed is unclear. Huge potash reserves have been found, and large-scale potash fertilizer production has begun, but the origin of these deposits is debated. Understanding the factors causing environmental evolution in this region is a central issue that will help us to clarify these and other debated issues. [Copyright &y& Elsevier]