Using high resolution data to reveal depth-dependent mechanisms that drive land subsidence: The Venice coast, Italy

Recent research has provided a high-resolution map that depicts the effect of land subsidence on the Venice coastal plain of Italy. The map, which covers the decade of 1992 to 2002, was obtained by an innovative “Subsidence Integrated Monitoring System” (SIMS), which efficiently merges the different displacement measurements obtained by high precision-leveling, differential and continuous Global Positing System data (GPS), and Synthetic Aperture Radar (SAR)-based interferometry. The displacement rates exhibit significant spatial variability, ranging from a slight 1 to 2 mm/yr uplift, to a serious subsidence of more than 10 mm/yr. This paper aims to describe the many natural and anthropogenic mechanisms that drive the pattern of the ground displacement. The movement sources are presented based on their depth of occurrence. Deep causes act at depths generally greater than 400 m below m.s.l. (mean sea level), and are recognizable in the movement of the pre-Quaternary basement. Medium causes act at depths between 400 and 50 m below m.s.l., and include geological features, such as a major presence of compressible clay layers in the southern and northern portions of the study area and groundwater withdrawals, mainly in the north-eastern coastland and western mainland. Shallow causes, i.e. those occurring from a depth of 50 m up to the ground surface, are related to the architecture and geomechanical properties of the Pleistocene and Holocene deposits, which are more thick and compressible approaching the littoral belt; geochemical compaction, due to the increasing salt concentration in the clayey sediments; and oxidation of the outcropping organic soils drained by land reclamation. These two latter factors primarily involve the southern portion of the Venice coast. The building loads in newly developed areas also cause local compaction of shallow deposits. We conclude that the consolidation of Holocene deposits and anthropogenic activities (groundwater withdrawal, land reclamation, and urban land use) are the major factors that contribute to the present land subsidence in the Venice coastland.     

国际地面沉降研究综述

文章在介绍国际地面沉降会议历史及２０００年第六届国际地面沉隆会议简况的基础上,并根据２０００年第六届国际地面沉降会议论文,对国际地面沉降研究进展情况分成如下六个方面进行了综述。地面沉降地质因素介绍了古代地面沉降、泥炭层沉降、地震砂土液化地面沉降和海平面上升研究状况。地下流体运移地面沉降方面介绍了以地下水开采为主的地面沉降问题及地面塌陷、天然气开采引起的地面沉降、均匀沉降对建筑结构的破坏和欠固结石英     

On causes and impacts of land subsidence in Bandung Basin, Indonesia

The Bandung Basin is a large intra-montane basin surrounded by volcanic highlands, in western Java, Indonesia, inhabited by more than seven million people. The basin, an area of about 2,300 km², is a highland plateau at approximately 650–700 m above sea level and is surrounded by up to 2,400 m high Late Tertiary and Quaternary volcanic terrain. Based on the results of nine GPS surveys conducted since 2000 up to 2011, it was shown that several locations in the Bandung Basin have experienced land subsidence, with an average rate of about ?8 cm/year and can go up to about ?23 cm/year in certain locations. A hypothesis has been proposed by several studies that land subsidence observed in several locations in the Bandung Basin has been caused mainly by excessive groundwater extraction. It is found that there is a strong correlation between the rates of groundwater level lowering with the GPS-derived rates of land subsidence in several locations in Bandung Basin. The GPS results in this study detected significant subsidence in the textile industry area, where very large volumes of groundwater are usually extracted. The impact of land subsidence in Bandung can be seen in several forms, mainly in the cracking and damage of houses, buildings and infrastructure. Land subsidence also aggravates the flooding in Bandung Basin, which has brought huge economic losses and deteriorated the quality of life and environment in the affected areas.     

基于InSAR技术的内蒙古巴彦淖尔市地面沉降演化特征及成因分析

巴彦淖尔市位于内蒙古自治区西部,区内第四系松散沉积层厚度大,具有发育地面沉降的基础条件。为填补该地区地面沉降研究的空白,利用PS-InSAR和SBAS-InSAR技术分别对巴彦淖尔市2007—2011年（ALOS PALSAR数据,98景）和2015—2016年（Radarsat-2数据,10景）的地面沉降情况进行定量...     

Land Subsidence of Jakarta (Indonesia) and its Geodetic Monitoring System

Jakarta is the capital city of Indonesia with a population of about 10 million people, inhabiting an area of about 25 × 25 km. It has been reported for sometime that locations in Jakarta are subsiding at different rates. Up to the present, there has been no comprehensive information about the characteristics and pattern of land subsidence in the Jakarta area. Usually land subsidence in Jakarta is measured using extensometers and ground water level observations, or estimated using geological and hydrological parameters. To give a better picture about land subsidence, geodetic-based monitoring systems utilizing leveling and GPS surveys have also been implemented.The land subsidence characteristics of Jakarta and its surrounding area areinvestigated using data from three repeated leveling surveys performed in1982, 1991, and 1997, and two repeated GPS surveys conducted in 1997and 1999. Leveling surveys detected subsidence up to about 80 cm duringthe period of 1982–1991, and up to about 160 cm during the 1991–1997period; while GPS surveys observed subsidence up to about 20 cm duringthe period of 1997–1999. Comparison with the hydrological data shows thatland subsidence in Jakarta is strongly related to excessive groundwater extraction.     

Geohistory analysis and basin development of the Neogene succession, NE Iraq

The Neogene succession in the studied area is represented by seven formations (Serikagni, Euphrates, Dhiban, Jeribe, Fatha, Injana, and Muqdadiya formations). The area of study is located in the Unstable Shelf within the Low Folded Zone and the north part of the Stable Shelf (Mesopotamian Zone). This study included the geohistory analysis of the Neogene succession and interpretation the changes of the accumulation and subsidence rates and compared them with the space available to explanation the basin development. At The Early Miocene (Aquitanian age), the Sirekagni and Euphrates formations was deposited during a major transgression with high rates of subsidence and accumulation in the Himreen, Makhul, and north of Tigris subzones, while the Chemchemal–Arbil and Butmah–Mosul subzones were positive areas. This period ended with a sea withdrawal to the southeast to generate the Dhiban lagoonal basin which was characterized by low accumulation and subsidence rates. During the Early Burdigalian, the Jeribe Formation was deposited during another sea level rise that covered the area except the Chemchemal–Arbil and Butmah–Mosul subzones representing the uplifted positive area. The sea level rise continued to the early Langhian age where the transition beds for the Fatha Formation was deposited to mark the maximum flooding surface covering all the study area. The Fatha Formation was deposited at the Late Langhian to the Early Serravallian during sea level stillstand with high accumulation and subsidence rates in the Himreen subzone and the Chemchemal–Arbil subzone. This period ended without a clear tectonic activity. The period from Late Miocene to Pliocene was characterized by high tectonic activity and sea level fall where fluvial–lacustrine environment prevailed to deposit the Injana and Muqdadiya formations. The Injana Formation was deposited during the Late Serravallian–Tortonian in the Himreen and Chemchemal–Butmah subzones; in addition to the northern part of Tigris subzone. The areas of high rates of accumulation and subsidence were located near Jambour while the southwestern part was affected by an uplift generating the Himreen structure. The Chemchemal–Butmah subzones was characterized by a high uplift in the southeast part where Kirkuk and Chemchemal structures were forming, while The northeastern part (from Bi Hassan to the borehole Kirkuk-117) was with low accumulation and subsidence rates. The linear region between these parts (Khabaz oil field) showed an abnormal values for accumulation and subsidence rates (very high); this region corresponds to the location and direction of Anah–Fatha–Qalat Dizah Fault which suggest that the fault was active during that time. The tectonic activity continued to uplift all the north of the study area as well as the West and the East during the Late Tortonian to the Piacenzian where the Muqdadiya Formation was deposited in the area between Jambour to Khabaz oilfields. Then the succession was deformed and uplifted to approximately 800 m above the sea level as in the present day.     

京杭运河长沟船闸工程地质灾害危险性评估

长沟船闸工程是“南水北调”东线工程京杭运河山东济宁-东平湖段复航工程的配套工程,标准二级船闸,设计年单向通过能力为2120～ 2440万t.项目征地范围平面图形为不规则长条型,面积559700m2,地质灾害危险性评估范围为征地范围向东、南、西、北四方向外扩200m,评估区面积为2774097m2.项目地质环境条件复杂程...     

Investigation of land subsidence due to groundwater withdraw in Rafsanjan plain using GIS software

Nowadays, the purpose of predicting land subsidence is to manage the optimum usage of groundwater, which is considered according to irregular use of groundwater. Digging deep and semi-deep wells and continuous drought, mainly in wasteland and semi-wasteland zone in recent years causes the land subsidence in Rafsanjan plain. The Rafsanjan basin is located in the nearly central part of Iran in the Kerman province, with a general elevation between 1,400–1,500 m above sea level. In this research, first, the deep and semi-deep wells were investigated and groundwater table data were colleted. Second, these informations were analyzed and corrected. These data were used to create great bank of information data, to manage and program the geographic information system (GIS) software. Then by investigation of an existing land subsidence data, which were collected by GPS in August 1998 and April 1999, by the GIS software, the results show that discharging of groundwater is the main factor of the land subsidence in Rafsanjan zone. Therefore, the critical land subsidence zone of the Rafsanjan plain was determined, and precaution and recommendations are presented.     

大地测量学的进展和我们的任务

在回顾现代大地测量和我国大地测量工作历史的基础上,对90年代我国大地测量任务,其中包括国家二期一等水准复测;国家GPS网布设;重力场参数精化;GPS卫星追踪站建立;沿海地区陆海相对垂直位移研究和青藏地区壳形变监测等理论和实践工作,作了论述。     

北京潮白河冲洪积扇地面沉降时空异质性特征及驱动因素分析

为了研究地面沉降的时空分布模式、机理机制,选择北京典型沉降区——潮白河冲洪积扇为研究区,采用PS-InSAR技术、莫兰指数及地理探测器,分析了研究区地面沉降的空间异质性特征,探测了不同特征下的地面沉降的主要驱动因素。结果表明：2017-01—2019-01研究区内地面沉降时空分布特征以一般沉降为主,沉降速率为[-133,3] mm/a,最大累积沉降量为261 mm,呈北部轻微、中部较严重、南部较轻的分布状态,其中,严重、极严重等级地面沉降主要分布在中游顺义后沙峪东部等地区及中下游交界地带的潞城镇;不同地区地面沉降呈现不同的空间异质性特征,即不均匀地面沉降分布特征明显,中游、下游均表现为低—低集聚;不同分布特征下地面沉降主要驱动因素不同,中游地区主要驱动因素为第二承压水水位变化和可压缩层厚度,下游主要驱动因素为浅层地下水水位变化和第一承压水水位变化。莫兰指数能够有效分析地面沉降空间异质性,识别集聚特征;地理探测器可以探明沉降空间异质性成因,获得其主要驱动因素。     

Monitoring land subsidence in Semarang,Indonesia

Semarang is one of the biggest cities in Indonesia and nowadays suffering from extended land subsidence, which is due to groundwater withdrawal, to natural consolidation of alluvium soil and to the load of constructions. Land subsidence causes damages to infrastructure, buildings, and results in tides moving into low-lying areas. Up to the present, there has been no comprehensive information about the land subsidence and its monitoring in Semarang. This paper examines digital elevation model (DEM) and benchmark data in Geographic Information System (GIS) raster operation for the monitoring of the land subsidence in Semarang. This method will predict and quantify the extent of subsidence in future years. The future land subsidence prediction is generated from the expected future DEM in GIS environment using ILWIS package. The procedure is useful especially in areas with scarce data. The resulting maps designate the area of land subsidence that increases rapidly and it is predicted that in 2020, an area of 27.5 ha will be situated 1.5–2.0 m below sea level. This calculation is based on the assumption that the rate of land subsidence is linear and no action is taken to protect the area from subsidence.     

基于时序InSAR和GPS技术的北京平原区地表三维形变场特征

文中采用InSAR与GPS技术相结合,获取了北京平原区时序地表三维形变场信息,分析了其分布特征与演化规律.研究表明:(1)北京平原区在抽水引发的第四系附加应力场作用下,地表呈现出显著的三维变形特征,以垂向变形为主,并辅以水平向位移.(2)平原区地面沉降主要集中在东部、北部和南部等地,存在多个沉降中心,总体呈减缓的趋势....     

北京地下水系统演化与地面沉降过程

采用地下水动态监测网、GPS监测网数据、气象监测数据与SAR数据、GIS等技术相结合,建立地下水系统演化与地面沉降过程模型,系统分析了北京地区地下水降落漏斗区地面沉降的形成过程。研究表明:降雨量呈逐年下降趋势,地下水开采量随之增大;平原区地下水位呈下降趋势,间接导致了地下水降落漏斗和地面沉降的形成演化。地面沉降对地下水降落漏斗的响应模式存在着季节与年际差异性,时空分布上存在不均匀性,最大地面沉降速率约为41.43 mm/a;揭示了地下水降落漏斗与地面沉降漏斗空间展布特性存在一致性,但并非完全吻合。     

论应用GPS定位技术监测上海市地面沉降的可行性

文章首先分析、论证了应用GPS定位技术监测地面沉降的理论依据，随后，介绍了实验研究方案和实际监测结果。通过比较GPS和精密水准所获得各个监测点的地面沉降量，以及两种不同方法获得地面沉降曲面的一致性，得出GPS沉降监测在一般监测环境下可能达到的精度。     

应对海平面上升与地面沉降迭加引发的地质灾害与生态环境问题

海平面上升已引起各国政府和科技界的高度关注。预计未来30年,浙江沿海海平面将比2009年升高88~140 mm。海平面上升与浙江沿海平原地面沉降迭加将进一步恶化地质与生态系统,引发许多灾害问题,制约沿海区域经济社会的可持续发展。本文主要就如何应对海平面上升与地面沉降迭加引发的地质灾害链与生态环境问题进行了探讨,认为要从地球系统科学角度,重视对陆-海相互作用机制与生态环境效应的研究,着手考虑建立陆海(包括入海河流)统筹的海岸带地质与生态环境监测评价系统。     

GPS在西安市地面沉降与地裂缝监测中的应用研究

本文从GPS监测网的布网原则和设计方案出发,对GPS外业观测和内业数据处理中的关键技术进行了深入研究,提出了一套适用于大城市地面沉降与地裂缝灾害监测的作业方法和数据处理方案。通过西安地区地面沉降和地裂缝的GPS监测实践,证明了本文提出的监测网的布设原则、GPS外业施测和内业数据处理方案是切实可行的,并且通过GPS监测获取了西安地面沉降和地裂缝近期活动的有关数据信息,且其与精密水准结果具有很好的一致性。     

INSAR技术在北京来广营地区地面沉降监测中的应用

北京市平原地区地面沉降危害日益显著,合成孔径雷达干涉测量（InSAR）具有快速、高精度、周期短等优势,可为城市地面沉降监测提供有效的技术手段。本文选用ENVISAT-1卫星SAR数据监测研究2004-2005年北京来广营地区地面沉降,利用InSAR差分技术得到该地区地面沉降监测结果。     

大范围地面沉降的差分GPS监测法

详细介绍了差分GPS静态测量和动态测量两种测量模式应用于大范围地面沉降监测的工作原理,探讨了GPS测量与水准测量,这两种方法因测量基准面不同,而使得所测地面沉降量存在的差异。将差分GPS静态测量模式实际应用于天津市的地面沉降监测,通过对其4年的实际测量精度的分析表明,对于大范围地面沉降监测,采用差分GPS静态测量法取代长距离的一等精密水准测量是完全可行的。     

台湾地面沉降及其监测控制

台湾地面沉降始于20世纪50年代，主要集中于西部沿海平原，沉降面积达1165km^2，约占平原区的1／10，目前以彰化、屏东等地较为严重，最大累积沉降量达3．2m，最大沉降速率为17．6cm/a。台湾地面沉降主要因开采地下水引起。目前采用GPS、一孔多标感应分层监测等技术实施地面沉降监测，通过用水规划制定与监督导实施地面沉降的控制与管理。     

Modelling the geoid and sea-surface topography in coastal areas

This paper looks at the relation between the time-averaged level of the sea surface and a gravimertic geoid, as determined in coastal areas. Measurements in local regions can now be accurate enough to demonstrate that the geoid and mean sea level are not even parallel to each other, let alone identical. The accuracy and pattern structure of surface gravity data in some shelf seas is comparable with those on land, so that a marine geoid can be derived from surface data without using satellite altimetry. The geodetic objective is then to combine the two to determine sea surface topography. In principle, gravimetric studies provide the absolute datum so that local oceanographic models on the shelf can be combined with sea surface topography models related to the global ocean circulation. In contrast, sea surface topography information near deep ocean coasts must come from external sources and satellite altimetry used to give the gravity data needed to offset the less good coverage by ship-borne gravimetry.Marine Bouguer anomalies enable two specific problems of gravity anomaly patterns near the continent ocean transition to be overcome. The necessary extension of Stokes' condensation reduction is developed and illustrated along a north-south profile from the Mediterranean across the Cote d'Azur. The effect on gravity of deep ocean water introduces a geoid correction in the form of a dipolar ridge whose amplitude at the shore is about 11 cm. In addition to geostrophic currents, a semi-quantitative model for the thermohaline effects on sea surface topography is discussed in relation to sea level differences between the Atlantic and Mediterranean.In considering appropriate algorithms for local geoid computation, Kirby's Iterative Fourier Combination routine for combining altimetry and surface gravity is extended to account for global sea surface topography. The impact of very fast spherical harmonic analysis algorithms is discussed and a simple physical model is given which explains the short coherence lengths found for the global gravity field. This necessary assumption for any local geoid computation was hitherto purely empirical.Finally, the use of land data such as tide gauges, ellipsoidal heights from GPS, and orthometric heights from first order levelling are reviewed as ways of corroborating geodetic estimates of sea surface topography and its relation to levelling datums. Successful examples are given from southern England.