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Because of its tectonic setting, the Paci"c coast of Colombia is subject to a variety of geological hazards, including earthquakes, tsunamis and associated phenomena such as regional and local coastal subsidence, #ooding and soil liquefaction. Erosional trends are prevalent along much of the 700 km long, low barrier island's shorelines of the Paci"c littoral and land losses are enhanced by factors such as 30 cm regional sea level rises associated to the occurrence of El Nin8o. Marine erosion is threatening more seashore littoral villages and worsening the already di$cult socioeconomic conditions of most part of the inhabitants. Because of diverse and strong motivations to stay near the sea, the responses of barriers island's inhabitants to marine erosion has consisted in most cases of repetitive in-shore and along-shore directed relocations of villages, rather than de"nitive abandonment of the islands. In the long run, this procedure only has postponed the problem and led to repetitive relocations and economical losses. The recent inland relocation of El Choncho village, on the San Juan River delta, illustrates a di!erent response to marine erosion. Although a new along-shore relocation was physically possible, inhabitants decided to abandon the barrier island and migrate to an interior, ancient beach ridge complex, applying a prudent solution which will be the most appropriate for other threatened villages of the Paci"c littoral. A detailed geomorphologic mapping program must be conducted in order to identify appropriate sites for inland relocation of existing villages on the barriers islands of the Colombian Paci"c coast. ( 2000 Elsevier Science Ltd. All rights reserved.

天津是中國遭受地面沉降最嚴重的城市之一。由於經濟與城市化的快速發展，新的沉降中心陸續出現在天津的郊區城鎮。本文結合L-和X-波段合成孔徑雷達(Synthetic Aperture Radar, SAR)資料，利用雷達干涉測量(SAR Interferometry, InSAR)時間序列分析，旨在加強天津郊區的沉降監測能力。先進的基於SAR資料的遙感技術，永久散射體干涉測量(Permanent Scatterers, PS)技術被證明是一種有效的，大範圍的，低成本的沉降監測手段。, 工作在X波段(波長為3.1cm)的TerraSAR (TSX)衛星可以提供新一代具有高解析度(1米)和短重放週期(11天)的SAR資料，從而能夠更快的獲取適用於干涉的時間序列的資料，並且適用於單個建築物的沉降觀測。然而，利用X-波段在森林或植被覆蓋區域並不能得到有效資訊。ALOS衛星的SAR感測器工作在L波段，由於波長更長(波長為23cm)，穿透力更強，所以在植被覆蓋區域也具有良好的相干性。但是ALOS衛星的SAR資料解析度更低(7米)，重放週期更長(46天)。從這兩個波段的資料特徵來看，他們可以被認為是互補的。所以，結合這兩個波段的資料可以增強沉降監測的能力和提供更為可靠的結果。儘管ALOS衛星於2011年4月22日停止了工作，我們的研究結果仍然可以為結合不同波段的SAR資料進行沉降監測提供普遍適用的結論，並為以後的研究工作提供參考。, 在研究中，我們提出了結合L和X波段的InSAR時間序列分析策略。此策略不僅可以作為X波段資料最優化獲取方案，而且可以成為快速，高精度，低成本，多級，大範圍監測策略。, 其次，我們基於多時序SAR資料，利用PS和准PS(Quasi-PS, QPS)技術進行了L波段與X波段的沉降監測能力探尋。L波段和X波段的時間序列分析所得到的沉降模式有很好的吻合性，都監測出三個主要的沉降中心，其中包括一個新近發現的沉降中心位於南河鎮。, X波段的PS分析結果顯示出高密度的PS點，證實了它可以用於同時監測星狀分佈的多個城鎮。結果也表明了高解析度TSX資料可以監測到線狀地物如鐵路，高速公路以及電力線的細節資訊和沉降資訊，這些可以成為高解析度PS技術在中國的重要應用。, 除此之外，我們利用水準資料驗證了L和X波段的處理結果，並且對地面沉降的過程進行了研究。由於水準資料和PS監測結果在時間和空間維上的採樣差別很大，所以我們對這兩者比較所具有的不確定性進行了詳細分析。結果表明了這兩種監測資料具有很好的一致性。, 最後，我們發現在天津抽取地下水是引起地面沉降的一個主要原因。根據PS結果和地質資料，我們發現地質因素可能是另一個用於解釋沉降中心位置和形狀的原因。, The aim of this dissertation is to enhance the capability of monitoring subsidence in Tianjin suburbs by combining L- and X-band Synthetic Aperture Radar (SAR) data with Interferometry (InSAR) time series analysis. Tianjin is located in one of the major subsidence regions in China and several new subsiding centers have been found in the suburbs of Tianjin. Advanced remote sensing technique, Permanent Scatterers (PS) based on SAR data has been found to be a feasible way to detect and monitor wide area ground subsidence at a low cost., TerraSAR X-band (TSX) of short wavelength (3.1 cm) provides new generation SAR data with high spatial resolution of 1 m and short revisit period of 11 days. It maintains the capability to fast build up interferometric stack, and to measure the subsidence of individual features, while almost no information can be detected with X-band in the forested and vegetated areas. ALOS L-band signal of longer wavelength (23cm) penetrates deeper into the vegetation cover and depicts higher coherence over non-urban areas, while the spatial resolution is relatively lower (7m) and revisit time is longer (46 days). The characteristics of these two bands can be regarded as complementary. Combining L- and X-band can enhance abilities of subsidence monitoring and provide more reliable results. Although ALOS died on April 22, 2011, this research work will provide general answers for combining different bands of SAR data to monitor subsidence, and give suggestions for future research work., In this research work, we have developed the strategy of combining L- and X-band with InSAR time series analysis. This strategy can not only be an optimized X-band acquisition plan, but also be a multi-level wide area monitoring strategy of subsidence with fast extraction, high precision and low cost., Moreover, with multi-temporal SAR data, we also investigate monitoring abilities of L- and X-band by exploring PS and Quasi-PS (QPS) techniques. The subsidence patterns derived from L- and X-band InSAR time series analysis are observed to have a good agreement. Three severe land subsidence zones were detected, containing one newly discovered subsiding center located in Nanhe Town., The X-band PS analysis shows high density of PS points and confirms its strong ability for simultaneously monitoring subsidence over star-like-distributed multiple towns. The results also demonstrate that linear constructions such as railways, highways and power lines can be detected in detail with high resolution TSX SAR data and indicates the deformation monitoring capability for large-scale man-made linear features which is a key application in China., Furthermore, L- and X-band results were independently validated with leveling data and ground motion processes were studied. The uncertainties were comprehensively analyzed between PS results and ground leveling data, whose densities are very different in both spatial and temporal domains. The overall results show a good agreement with each other., Finally, we find that underground water extraction is one of the major reasons for ground subsidence in Tianjin. In addition, with the integrated analysis of the PS results and the geological data, we found that lithological characteristics may be another important reason to explain location and shape of the subsiding centers., Detailed summary in vernacular field only., Luo, Qingli., Thesis (Ph.D.)--Chinese University of Hong Kong, 2013., Includes bibliographical references (leaves 103-112)., also in Chinese., p.I, TABLE OF CONTENT --- p.VI, List of Figures --- p.VIII, List of Tables --- p.XI, List of abbreviations --- p.XII, ACKNOWLEDGEMENT --- p.XIV, Chapter 1 --- INTRODUCTION --- p.1, Chapter 1.1 --- Thesis contributions --- p.6, Chapter 1.2 --- Thesis structure --- p.7, Chapter 2 --- BACKGROUND --- p.9, Chapter 2.1 --- Synthetic Aperture Radar (SAR) --- p.9, Chapter 2.1.1 --- SAR imaging geometry --- p.9, Chapter 2.1.2 --- SAR satellites --- p.10, Chapter 2.2 --- Synthetic Aperture Radar Interferometry (InSAR) --- p.13, Chapter 2.2.1 --- Introduction --- p.13, Chapter 2.2.2 --- Principles of InSAR --- p.13, Chapter 2.3 --- Differential Synthetic Aperture Radar Interferometry (D-InSAR) --- p.18, Chapter 2.3.1 --- D-InSAR principle --- p.18, Chapter 2.3.2 --- The advantages and Limits of interferometric measurements --- p.21, Chapter 2.4.3 --- The development of PS technique --- p.22, Chapter 2.4 --- Persistent Scatterers Interferometry (PSI) --- p.24, Chapter 2.4.1 --- Permanent Scatterers (PS) Technique and Advantages --- p.24, Chapter 2.4.2 --- Principle of PS technique --- p.26, Chapter 2.5 --- QPS (Quasi-PS) Interferometry --- p.28, Chapter 3 --- MULTI IMAGES INSAR ANALYSIS OF TIANJIN --- p.31, Chapter 3.1 --- Introduction --- p.32, Chapter 3.2 --- Study area and SAR data --- p.34, Chapter 3.3 --- X-band optimized acquisition planning combing with L-band --- p.38, Chapter 3.3.1 --- The strategy --- p.38, Chapter 3.3.2 --- Experimental results and analyzes --- p.40, Chapter 3.4 --- Estimating deformation maps with L- and X-band --- p.45, Chapter 3.4.1 --- Monitoring subsidence over multiple towns and large man-made linear features with X-band --- p.45, Chapter 3.4.2 --- The L-band QPS Results --- p.56, Chapter 3.5 --- Conclusions --- p.58, Chapter 4 --- VALIDATION AND INTERPRETAION --- p.61, Chapter 4.1 --- Introduction --- p.61, Chapter 4.2 --- Validation --- p.61, Chapter 4.2.1 --- Leveling data --- p.61, Chapter 4.2.2 --- Uncertainties analysis --- p.64, Chapter 4.2.3 --- Average velocity comparison --- p.66, Chapter 4.2.4 --- Annual displacement comparison --- p.68, Chapter 4.2.5 --- Deformation time series: InSAR results and leveling --- p.70, Chapter 4.2.6 --- Average velocity map comparison between InSAR results and leveling --- p.71, Chapter 4.2.7 --- Displacement comparison between InSAR results and GNSS data --- p.73, Chapter 4.2.8 --- Average velocity comparison between ALOS results and leveling --- p.73, Chapter 4.3 --- Geological Interpretation --- p.74, Chapter 4.4 --- Field survey --- p.77, Chapter 4.5 --- QPS points analysis with aerophotograph --- p.81, Chapter 4.6 --- Conclusions --- p.84, Chapter 5 --- VALIDATION ALONG RAILWAY --- p.87, Chapter 5.1 --- Introduction --- p.87, Chapter 5.2 --- Study area --- p.87, Chapter 5.3 --- The validation plan --- p.87, Chapter 5.4 --- Validation with leveling data --- p.89, Chapter 5.4.1 --- Leveling data --- p.89, Chapter 5.4.2 --- The average subsidence rate comparison --- p.91, Chapter 5.4.3 --- The displacement comparison --- p.95, Chapter 5.5 --- Conclusions --- p.97, Chapter 6 --- SUMMARY --- p.98, The Publications --- p.102, REFERENCES --- p.103, http://library.cuhk.edu.hk/record=b5549824, Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)

After a brief review of a number of developments of unsaturated soil mechanics, the paper presents some applications to engineering problems. The first case involves the collapse of a residual soil in Brazil triggered by a water level increase caused by the filling of a dam reservoir. The second case analyzes the effects of rainfall on a natural slope in Ancona (Italy). The final case refers to the subsidence in the region of Ravenna related to the depletion of deep gas reservoirs. The ensemble of the cases described illustrates the potential of unsaturated soil mechanics concepts for the understanding and reproduction of observed field behaviour., Postprint (published version)

Megalopolises in the Pearl River Delta, including Guangzhou and Hong Kong, have experienced various degree of ground subsidence. The causes can be divided into two categories: natural subsidence and the human-induced subsidence. Monitoring the ground subsidence can not only help people to find out the distributions in both spatial and temporal fields, but also guide people to minimize the hazard ahead. Thus, it is significant to monitor the ground subsidence accurately, timely and frequently. This dissertation research uses the Environmental Satellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) data received at the Chinese University of Hong Kong Satellite Remote Sensing Receiving Station and SAR Interferometry (InSAR) technology as a powerful tool for large-scale ground deformation monitoring in Guangzhou and Hong Kong areas., Persistent Scatterer Interferometry (PSI) method is used to detect ground deformation in the urban area of Guangzhou city. A ground deformation rate map with scattered distribution of point targets shows the maximum subsidence (rise) rate as high as -26 to -20 mma-1 (16-21 mma-1 ), implying that the study area is an active zone for ground deformation. Based on the point target map, a contour ground deformation rate map is generated. All the six ground collapse accidents that occurred in 2007-2008 fall within the subsidence zones, qualitatively validating the IPTA results. Ground subsidence and geological conditions on Datansha Island are examined. The results indicate that the local geological conditions and underground engineering projects are responsible for ground subsidence and ground collapse accidents occurred there. To interpret the distribution of active ground subsidence zones, a local geological map is used as a reference for generating a series of thematic maps. The results show that geological faults, rock distribution, over-development, and underground engineering projects may be four factors leading to the distribution of the active ground subsidence zones., The Hong Kong International Airport (HKIA) was built on a site of 12.5 km2, of which 75% is reclaimed foundation. Thus, the stability of ground foundation of HKIA is of public concern. I use the PSI method and ENVISAT ASAR data to detect the residual settlement rate from 19 April 2006 to 9 January 2008. I use ground truth data to develop empirical correction models for correcting systematic biases in the ASAR PSI-detected settlement rate. The corrected data follow the Lorentz distribution well, implying that the residual settlement process is dominated by two modes or categories of settlement rates. I find unreasonable positive values of the ASAR PSI-detected annual ground settlement rate, which follow a normal distribution. I draw a scatter plot with ground deformation rate value and coherence value of each point targets. Point targets with lower coherence values and greater positive values are extracted and drawn on a geographical map. Most of these point targets are located at the airport Midfield, which is under construction. A ground settlement rate map of HKIA shows that an area of the Passenger Terminal Building, and an area of the Southern Runway are two relatively stable areas, and one major continuous settlement area covers the airport Midfield. General spatial distribution patterns of ASAR PSI-detected ground settlement rate agree well with model-predicted residual settlement rates., Zhao, Qing., Adviser: Lin Hui., Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: ., Thesis (Ph.D.)--Chinese University of Hong Kong, 2010., Includes bibliographical references (leaves 147-163)., Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web., Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web., also in Chinese., isbn: 9781124494326, Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)