The Coupling Relationship between the Uplift of Longmen Shan and the Subsidence of Foreland Basin,Sichuan,China

Depending on the analysis of the coeval sedimentary geometry and subsidence mechanism in the Longmen Shan foreland basin, three models about the coupling relationship between Longmen Shan uplift and foreland basin subsidence since the Indosinian have been proposed：（1） crustal shortening and its related wide wedge-shaped foreland basin,（2） crustal isostatic rebound and its related tabular foreland basin, and（3） lower crustal flow and its related narrow wedge-shaped foreland basin. Based on the narrow wedge-shaped foreland basin developed since 4 Ma, it is believed that the narrow crustal shortening and tectonic load driven by lower crustal flow is a primary driver for the present Longmen Shan uplift and the Wenchuan（Ms 8.0） earthquake.

The Uplift of the Longmenshan Thrust Belt and Subsidence of the West Sichuan Foreland Basin

Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e. the rapid uplifting of the the Songpan-Garze fold belt was corresponding to the rapid subsidence of the basin;the Songpan-Garze fold belt has uplifted at a much greater rate than the West Sichuan foeland basin in the last 60 Ma;and (7) the palaeogeothermal gradient was 25℃ /km in the West Sichuan foreland basin.

Interpreting the Coseismic Uplift and Subsidence of the Longmen Shan Foreland Basin System during the Wenchuan Earthquake by a Elastic Flexural Model

The coseismic surface uplift of the Longmen Shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness（Te） of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence（-40–70 cm） at the front of the LMS is evidently lower than the observed values（-100 cm）, suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS.

Differences and controlling factors of composite hydrocarbon accumulations in the Tazhong uplift, Tarim Basin, NW China

Based on three-dimensional seismic interpretation, structural and sedimentary feature analysis, and examination of fluid properties and production dynamics, the regularity and main controlling factors of hydrocarbon accumulation in the Tazhong uplift, Tarim Basin are investigated. The results show that the oil and gas in the Tazhong uplift has the characteristics of complex accumulation mainly controlled by faults, and more than 80% of the oil and gas reserves are enriched along fault zones. There are large thrust and strike-slip faults in the Tazhong uplift, and the coupling relationship between the formation and evolution of the faults and accumulation determine the difference in complex oil and gas accumulations. The active scale and stage of faults determine the fullness of the traps and the balance of the phase, that is, the blocking of the transport system, the insufficient filling of oil and gas, and the unsteady state of fluid accumulation are dependent on the faults. The multi-period tectonic sedimentary evolution controls the differences of trap conditions in the fault zones, and the multi-phase hydrocarbon migration and accumulation causes the differences of fluid distribution in the fault zones. The theory of differential oil and gas accumulation controlled by fault is the key to the overall evaluation, three-dimensional development and discovery of new reserves in the Tazhong uplift.

A geometrically and locally adaptive remeshing method for finite difference modeling of mining-induced surface subsidence

Surface subsidence induced by underground mining is a typical serious geohazard.Numerical approaches such as the discrete element method(DEM)and finite difference method(FDM)have been widely used to model and analyze mining-induced surface subsidence.However,the DEM is typically computationally expensive,and is not capable of analyzing large-scale problems,while the mesh distortion may occur in the FDM modeling of largely deformed surface subsidence.To address the above problems,this paper presents a geometrically and locally adaptive remeshing method for the FDM modeling of largely deformed surface subsidence induced by underground mining.The essential ideas behind the proposed method are as follows:(i)Geometrical features of elements(i.e.the mesh quality),rather than the calculation errors,are employed as the indicator for determining whether to conduct the remeshing;and(ii)Distorted meshes with multiple attributes,rather than those with only a single attribute,are locally regenerated.In the proposed method,the distorted meshes are first adaptively determined based on the mesh quality,and then removed from the original mesh model.The tetrahedral mesh in the distorted area is first regenerated,and then the physical field variables of old mesh are transferred to the new mesh.The numerical calculation process recovers when finishing the regeneration and transformation.To verify the effectiveness of the proposed method,the surface deformation of the Yanqianshan iron mine,Liaoning Province,China,is numerically investigated by utilizing the proposed method,and compared with the numerical results of the DEM modeling.Moreover,the proposed method is applied to predicting the surface subsidence in Anjialing No.1 Underground Mine,Shanxi Province,China.

Finite-difference model of land subsidence caused by cluster loads in Zhengzhou,China

Groundwater exploitation has been regarded as the main reason for land subsidence in China and thus receives considerable attention from the government and the academic community.Recently,building loads have been identified as another important factor of land subsidence,but researches in this sector have lagged.The effect of a single building load on land subsidence was neglected in many cases owing to the narrow scope and the limited depth of the additional stress in stratum.However,due to the superposition of stresses between buildings,the additional stress of cluster loads is greater than that of a single building load under the same condition,so that the land subsidence caused by cluster loads cannot be neglected.Taking Shamen village in the north of Zhengzhou,China,as an example,a finite-difference model based on the Biot consolidation theory to calculate the land subsidence caused by cluster loads was established in this paper.Cluster loads present the characteristics of large-area loads,and the land subsidence caused by cluster loads can have multiple primary consolidation processes due to the stress superposition of different buildings was shown by the simulation results.Pore water migration distances are longer when the cluster loads with high plot ratio are imposed,so that consolidation takes longer time.The higher the plot ratio is,the deeper the effective deformation is,and thus the greater the land subsidence is.A higher plot ratio also increases the contribution that the deeper stratigraphic layers make to land subsidence.Contrary to the calculated results of land subsidence caused by cluster loads and groundwater recession,the percentage of settlement caused by cluster loads in the total settlement was 49.43%and 55.06%at two simulated monitoring points,respectively.These data suggest that the cluster loads can be one of the main causes of land subsidence.

Geochemical characteristics of Sr isotopes in the LS33 drill core from the Qiongdongnan Basin, South China Sea, and their response to the uplift of the Tibetan Plateau

Making full use of modern analytical and testing techniques to explore and establish new indexes or methods for extracting paleoseawater geochemical information from sediments will help to reconstruct the sedimentary paleoenvironment in different research areas.The connection between the subsidence of the South China Sea basin and the uplift of the Tibetan Plateau has been a scientific concern in recent decades.To explore the information on the sedimentary paleoenvironment,provenance changes and uplift of Tibetan Plateau contained in core sediments(debris),we selected core samples from Well LS33 in the Qiongdongnan Basin,South China Sea,and analyzed the contents of typical elements(Al,Th,and rare earth elements)that can indicate changes in provenance and the Sr isotopic compositions,which can reveal the geochemical characteristics of the paleoseawater depending on the type of material(authigenic carbonate and terrigenous detritus).The results show the following:(1)during the late Miocene,the Red River transported a large amount of detrital sediments from the ancient continental block(South China)to the Qiongdongnan Basin.(2)The authigenic carbonates accurately record changes in the 87Sr/86Sr ratios in the South China Sea since the Oligocene.These ratios reflect the semi-closed marginal sea environment of the South China Sea(relative to the ocean)and the sedimentary paleoenvironment evolution process of the deep-water area of the Qiongdongnan Basin from continental to transitional and then to bathyal.(3)Since the Neogene,the variations in the 87Sr/86Sr ratio in the authigenic carbonates have been consistent with the variations in the uplift rate of the Tibetan Plateau and the sediment accumulation rate in the Qiongdongnan Basin.These consistent changes indicate the complex geological process of the change in the rock weathering intensity and terrigenous Sr flux caused by changes in the uplift rate of the Tibetan Plateau,which influence the Sr isotope composition of seawater.

The Fault Block's Framework in Boli Basin and its Control Over the Deposition

Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault-fold remnant basin. The basin’s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks’ dis- placement features rusulted from by the movement of the edge faults and the main basement faults.

The Activity of Major Faults and the Hydrothermal Alteration Zone at Tianchi Volcano of Changbaishan

It is found by field investigation that the near horizontal top surface of the brown or brick-red hydrothermal alteration zone varies obviously in elevation at different sections of the same layer on the caldera’s inner wall of Tianchi, with that at the north section near the Tianwen Peak about 110 m higher than that at the south near the Jiangjun Peak in Korea. The top surface of the hydrothermal alteration zone can be taken as key horizon to tectonic movement. The difference indicates that the total uplift height of the NW wall of the Liudaogou-Tianchi-Jingfengshan fault, the principal fault trending NE at Tianchi, is bigger than that of the SE wall ever since the occurrence of hydrothermal alteration. This also explains why the topography in the northwest side of Tianchi is steeper and with more developed river system than in the southeast. The uplifting of the northeastern wall is bigger than that of the southwest along the principal NW-trend fault, namely, the Baishanzhen-Tianchi-Jince fault. It is observed from characters of hydrothermal alteration and the palaeoresiduum, that the recent vertical movement rate along the principal NE-trend fault is larger than that of the principal NW-trend fault. The two faults intersect at Tianchi, dividing the volcano into 4 blocks, with the uplift magnitudes decreasing successively in the order of the north, the west, the east and the south block. The biggest uplift of the north block corresponds well to the shallow magma batch in the north of Tianchi observed by DSS and telluric electromagnetic sounding, and etc. and they may be related with the causes.

基于Landsat TM/OLI影像的兖州煤田水域面积动态监测

为揭示东部高潜水位矿区地表水体的时空演变规律,该文以兖州煤田为研究区,在比较改进归一化差异水体指数法、单波段阈值法、谱间关系法、K-T变换4种水体提取方法的精度及优缺点基础上,采用基于阈值分割的改进的归一化差异水体指数法提取了研究区1990-2014年的水体信息并分析了其时空变化特征。研究结果表明:从1990-2009年,兖州煤田地表水域面积增加了1 696.14 hm^2,且2001-2005年水域面积扩张速度较快,年均增长率达14.0%,2009-2014年水域面积减少,年均下降率为3%;煤炭开采是研究区内水域面积变化的主要驱动因子。该文实现了煤矿区地表水体变化的动态监测,并分析了其变化原因,有助于客观与定量地评估煤炭开采的生态累积效应。

基于Knothe时间函数和InSAR的煤矿区动态沉陷预计研究

以钱营孜矿区的3212工作面为研究对象,采用基于Knothe时间函数的动态沉陷预计模型进行开采沉陷动态预计。计算了不同时间、不同位置的点的动态下沉值,分别与水准测量成果和D-InSAR监测结果进行了对比分析。实验表明,基于Knothe时间函数的动态沉陷预计模型所得到的结果符合开采沉陷导致的地表沉陷规律;其结果与水准测量成果和D-InSAR监测结果吻合;最大误差不超过0.2m,能够满足动态预计的要求。

Upward surface movement above deep coal mines after closure and flooding of underground workings

After the mass closures of entire coal mine districts in Europe at the end of the last century, a new phenomenon of surface movement was observed—an upward movement.Although most surface movement(i.e., subsidence) occurs in the months and years after mining by the longwall method, surface movement still occurs many decades after mining is terminated.After the closure and flooding of underground excavations and surrounding rock, this movement was reversed.This paper focuses on quantifying the upward movement in two neighboring coal mines(Winterslag and Zwartberg, Belgium).The study is based on data from a remote sensing technique: interferometry with synthetic aperture radar(INSAR).The results of the study show that the rate of upward movement in the decade after closure is about 10 mm/year on average.The upward movements are not linked directly to the past exploitation directly underneath a location.The amounts of subsidence at specific locations are linked mainly to their positions relative to an inverse trough shape situated over the entire mined-out areas and their immediate surroundings.Local features, such as geological faults, can have a secondary effect on the local variation of the uplift.The processes of subsidence and uplift are based on completely different mechanisms.Subsidence is initiated by a caving process, while the process of uplift is clearly linked to flooding.

Various phases in surface movements linked to deep coal longwall mining:from start-up till the period after closure

This paper covers the entire lifetime of an underground coal mine,including the start-up of the mining operations and the period after the closure and sealing of the underground workings.Measurements of the vertical surface movement are presented for three neighbouring mines in the Belgian Campine coal basin,where the longwall mining method was applied.First,the monitoring of the initial phase showed that the impact of the first panel was smaller than the impacts of the following two neighbouring panels.When the second panel was mined,a change in the induced surface tilt was observed in the immediate proximity of the panels.Second,data for a transect with a length of about 2.5 km were presented,covering a total time of 54 years,of which the first 31 years were during the active life of the mine.Average subsidence rates of up to-0.3 m/year were observed.After the mine was closed and the pumping facilities were stopped,the average uplift rate was situated mostly between 4 and 16 mm/year,but a value of 141 mm/year also was measured.Thirty years after closure,the upward movements are still occurring.Third,the phase of uplift is analyzed in more detail over a full north–south transect.A clear narrow maximum was observed for the uplift,corresponding to a total vertical movement of 0.2 m over approximately an 18-year period.All these phases are relevant,for example when analysing damage to buildings and infrastructure.Damage becomes visible when the cumulative movement and loading exceed critical limits and not necessarily when the largest rate of movement is observed,for example.

震陷土层变化下变截面单、群桩动力响应差异

为研究地震动作用下震陷土层厚度不同时大直径变截面单桩与群桩基础的动力响应差异,依托厦门第二东通道翔安大桥,通过振动台模型试验,开展震陷土层厚度30、40、50 cm时,单桩与群桩基础桩周土震陷量、桩顶水平位移、桩身加速度及弯矩动力响应差异研究.结果表明:随着震陷层厚度增大,单桩与群桩基础桩周土震陷量、桩顶水平位移、桩身加速度及弯矩均逐渐增大,且加速度及弯矩在变截面处突变;同一震陷层厚度下,群桩基础桩周土震陷量较单桩大,但群桩基础加速度、桩顶水平位移及桩身弯矩均小于单桩.震陷场地桩基础设计时,应着重考虑变截面单桩与群桩动力响应差异,保证桩基础抗震性能.

基于多数据源的采煤沉陷区早期识别及地面形变特征监测——以神木市大柳塔镇为例

煤矿区生态环境问题受到社会的广泛关注,如何实现采煤沉陷区精准、高效、经济的早期识别和动态监测显得尤为迫切。本文在资料收集与整理分析的基础上,利用2000—2022年5期DEM数据进行差分解算,同时利用2015年6月15日至2023年7月15日共计164期长时间序列Sentinel-1数据,对煤矿区地面沉降进行动态监测,查明了神木市大柳塔镇采煤沉陷区现状分布与地面沉降特征,形成了一套基于多数据源的采煤沉陷区早期识别方法。研究结果表明:①大柳塔镇采煤沉陷区分布面积为252.70 km 2,包括地面塌陷、采空区悬顶两种类型,神华公司石圪台、哈拉沟、大柳塔、活鸡兔4大矿区煤矿塌陷问题严重;②将分辨率为2 m的DEM数据重采样为5 m后进行差值运算,误差为0.01 m,精度较高且计算高效;③DEM差分解算、SBAS-InSAR技术均能对地面塌陷范围进行精准识别,匹配度高,且各方法间互为补充,相互印证。

双向近场地震下结构性软黏土震陷特性研究

软黏土的震陷效应与土体的结构性有着密切联系,但目前关于土体的结构强度对震陷影响的研究还较少。自然界中很难获取到物质成分相同而结构性质不同的土,为了对P波和S波耦合作用下结构性软黏土的震陷特性进行深入研究,人工制备了物质成分相近而结构强度不同的软黏土,通过开展两组动态围压下的动三轴试验,探讨结构强度、双向动荷载和P波与S波的相位差对其震陷特性的影响规律。试验结果表明:双向激振下,轴向动荷载与结构屈服应力比值越大,双向动荷载的耦合对轴向残余应变积累速度的加速作用越明显;相位差对轴向残余应变的影响则取决于土体结构强度,结构强度越小,影响越大。双向近场地震中,径向动荷载一般会加速震陷的发展,加速作用的大小与土体结构强度大小有关,结构强度越小,加速作用越明显,但轴向动荷载的剪切作用对结构性软黏土的残余应变积累仍起主导作用。研究结果可为软土地区综合防灾提供有益参考。

基于短梁-弹簧模型的盾构隧道施工期上浮变形计算方法

盾构隧道在掘进过程中易出现管片上浮问题,为更加真实地描述施工期盾构隧道在上浮力作用下产生的管片环间错台变形和张开变形,提出基于短梁-弹簧模型的盾构隧道上浮变形理论计算方法。首先,引入Euler-Bernoulli短梁和环间接头弹簧模拟盾构隧道纵向结构,通过设置边界弹簧考虑盾构机盾尾对管片的任意约束作用;之后,采用有限差分理论推导得到施工期上浮力作用下盾构隧道上浮变形解答;最后,对比实际工程案例和数值模型结果以及传统等效梁计算结果验证了计算方法的正确性和有效性,并探明了理论计算模型中关键参数的敏感性,进一步讨论了浆液未凝固段长度、管片环间接头弹簧刚度以及地基弹性模量对隧道上浮变形规律的影响。研究结果表明:与传统连续梁模型结果相比,新方法可以真实地反映盾构隧道的非连续性变形性状,定量分析管片环环间的错台变形和张开变形;通过参数分析可知,浆液未凝固段长度的增长会明显增大盾构隧道上浮变形最大值和变形影响范围;适当提高环间接头的剪切刚度和转动刚度可以有效降低隧道上浮位移、管片环间错台变形和张开变形;在地基弹性模量较小的软弱地层中盾构隧道施工期的上浮变形更不易控制。

The Coupling Relationship between the West Shandong Rise and the Jiyang Depression, China

This article reports 21 AFT （apatite fission track） data from the West Shandong （山东） rise （WSR） and Jiyang （济阳） depression, and mainly studies their Cenozoic uplifting/subsidence history and the relationship between them. Furthermore, we improve our insights into the Bohai Bay Basin （BBB）. Our AFT analysis and AFT T-t modeling indicates that the WSR was uplifted at ca. 65 Ma with apparent uplift rate of 0.019 mm/a; it underwent two relatively rapid uplifting events at 43-33 and 16-0 Ma with rates of 0.097 and 0.052 mm/a, respectively. Meanwhile, the Jiyang depression subsided at rate of 0.032 mm/a at 52-43 Ma, and the rate increased to 0.13 mm/a at ca. 42-33 Ma; finally the subsidence rate increased to 0.053 mm/a in 16-0 Ma. They all underwent a uplift in time of 23-16 Ma with rate of 0.04-0.07 mm/a. A careful comparison shows that the Cenozoic uplifting of the WSR coupled well with the subsidence of the Jiyang depression. Our research also suggests that the uplift- basin coupling events are part of the couplings between the Bohai Bay Basin and its peripheral moun- tains. This intraplate mountain-basin coupling is a reflection of global tectonic events.

南水北调地下水回补对潮白河冲洪积扇中上部地表形变响应及控制因素

2014年南水进京后,持续开展地下水回补对于遏制和减缓地面沉降发展起到重要作用,但地下水回升由此带来的不同区域、不同层位的地面沉降与回弹机制及其控制因素尚不明确。深入探讨和研究回补时间、回补量、回补地点与水位及地表形变之间的关系,了解地表形变发生机理和识别主控因素,为后续如何科学回补,发挥最大化水资源回补效益、对地面沉降防治和超采区治理具有极其重要意义。笔者以潮白河冲洪积扇中上部区域为例,采用永久散射体差分干涉测量(PS-InSAR)技术获取研究区地面沉降形变信息,并结合区域分层地下水位动态变化、分层沉降变化等多手段进行耦合,查明研究区地表形变与多因素之间的响应与控制因素。结果表明:南水持续回补导致区域地面沉降减缓,并在牛栏山地区出现地表抬升,抬升范围也随着水位上升逐渐向中下游扩展,2022年最大回弹速率达46.9 mm/a;地表形变具有明显的受断裂所控制的第四系沉积差异特性,以黄庄—高丽营断裂、顺义断裂和南口—孙河断裂所分割的后沙峪凹陷范围内变化明显大于其他地区;地下水位变幅与富水性差异决定水位上升范围与响应变化,而沉积构造作用所造成第四系沉积差异在地下水流向上具有一定控制作用。结果为地面沉降防控和机理研究提供理论和科学依据,同时也为后续开展地下水科学回补和方案优化提供指导和借鉴。

珠江口盆地番禺低隆起新生代断裂体系及油气成藏潜力

番禺低隆起的油气勘探潜力受新生代断裂体系控制,目前对其断裂特征和演化过程的研究较为匮乏。利用覆盖番禺低隆起的三维地震资料,对研究区的结构特征、断裂平面展布、断裂剖面变形样式等进行分析;定量计算了新生代以来各洼陷边界断裂的活动速率,划分了断裂活动期次;对研究区新生代演化过程进行了复原,分析了不同时期断裂发育的动力学成因。结果表明:番禺低隆起各洼陷均为“南断北超”结构,控洼断裂沿走向的不连续导致洼陷具有多个沉积中心;控洼断裂新生代活动可划分为初始裂陷期、加速裂陷期、裂后拗陷期、构造复活期和构造平静期;其中,文昌组沉积期和韩江组下段沉积期为断层活动的两大高峰期;番禺低隆起新生代断裂的发育受到基底先存断裂的严格控制,断裂走向自深到浅发生顺时针偏转,与南海区域应力场的偏转密切相关。裂陷期断裂活动强烈,使得番禺低隆起具备发育优质烃源岩的潜力。