No description available.

No description available.

The objective of this thesis is to improve the knowledge of control mechanisms of hydrological induced mass movements. To this end, detailed hydrological process studies and physically-based hydrological modelling were applied. The study site is a hillslope in the Dornbirn Ache valley near Bregenz, Austria. This so called Heumös slope features a deep-seated translational shear zone and surface near creep movements of up to 10 cm a year. The Cretaceous marlstones of the Austrian Helveticum have a high susceptibility for weathering and might form clay-rich cohesive sediments. In addition, glacial and post-glacial processes formed an unstable hillslope. High yearly precipitation depths of about 2100 mm and rainstorms with both high intensities and precipitation depths govern surface and subsurface hydrological processes. Pressure propagation induced in hydrological active areas influences laterally the groundwater reactions of the moving mass. A complex three-dimensional subsurface pressure system is the cause for fast groundwater reactions despite low hydraulic conductivities. To understand hillslope scale variability, hydrotopes representing specific dominating processes were mapped using vegetation association distribution and soil core analysis. Detailed small-scale soil investigations followed to refine the understanding of these hydrotopes. A perceptional model was developed from the hydrotope distribution and was corroborated by these detailed investigations. The moving hillslope is dominated by surface-runoff generation. Infiltration and deep percolation of water is inhibited through clay-rich gleysols; the yearly average soil moisture is close to saturation. Steep slopes adjacent to the moving hillslope are far more active concerning infiltration, preferential flow and groundwater fluctuations. Spring discharge observations at the toe of the steep slopes are in close relation to groundwater table observations on the moving hillslope body. Evidence of pressure propagation from the steep slopes towards the hillslope body is gathered by comparison of dominating structures and processes. The application of the physically-based hydrological model CATFLOW substantiates the idea of pressure propagation as a key process for groundwater reactions and as a possible trigger for movement in the hillslope. / Diese Arbeit soll die Zusammenhänge von hydrologischen Rahmenbedingungen und Massenbewegungen besser erforschen, damit in Zukunft verbesserte Vorhersagen des Versagenszeitpunktes möglich werden. Das Untersuchungsgebiet besteht aus einem ca. 2 km langen und 500 m breiten Hang mit einem maximalen Höhenunterschied von ca. 400 m. Das dort vorkommende Festgestein besteht im Wesentlichen aus Mergelstein. Die vergangenen Eiszeiten haben dieses Gestein überarbeitet und Grundmoränenablagerungen auf dem Hang zurückgelassen. Diese wurden in den letzen 10.000 Jahren von Hangschutt, der aus den benachbarten Steilhängen stammt, überlagert. Der Hangschutt ist sehr verwitterungsanfällig, die Kalkkristalle lösen sich und wandeln den Hangschutt in lehmiges Material. Bewegungsmessungen an der Oberfläche zeigen, dass sich der Hang mit ca. 10 cm im Jahr talabwärts bewegt. Diese Bewegungen werden sehr wahrscheinlich durch kleine ruckartige Ereignisse in ca. 8 m Tiefe ausgelöst. Ziel der Untersuchungen war, den Wasserhaushalt des Hanges so gut wie möglich zu erfassen und mit Computermodellen abzubilden. Dabei spielt die Heterogenität der pedologischen Eigenschaften einen wesentliche Rolle, als Eingangsparameter für die Modelle. Grundwasserstandsmessungen in 5,5 m Tiefe auf dem Hang zeigen schnelle Reaktionen des Grundwasserspiegels nach Niederschlagsereignissen. Das Wasser dieser Ereignisse kann aber aufgrund des Lehms, der nur eine geringe Wasserdurchlässigkeit für Wasser besitzt, nicht in den tieferen Untergrund gelangen, sondern fließt fast vollständig an der Oberfläche ab. Dahingegen führt ein schnelles Versickern von Wasser in an den Hang anschließenden Steilhängen zu einem schnellen Grundwasseranstieg, der aufgrund eines gespannten Grundwasserleiters den Druck in die Hangrutschung weitergibt. Dort wird ein Überdruck aufgebaut, der sehr wahrscheinlich die Bewegungen auslöst. Die vorliegende Arbeit ist eine detaillierte Herangehensweise um Erkenntnisse aus der Hyrologie für die Bestimmung des Wasserhaushaltes von Massenbewegungen heranzuziehen.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22125号 / 工博第4655号 / 新制||工||1726(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 角 哲也, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

Ce projet de recherche vise à accroître les connaissances sur les mécanismes contrôlant la déformation des glissements de terrain argileux grâce à la combinaison de la surveillance sismique passive et de la surveillance géodésique. Des études récentes ont démontré que la surveillance sismique peut fournir des informations intéressantes sur la mécanique des glissements de terrain et, dans certains cas, fournir des précurseurs utiles pour la prévision des défaillances. L’installation récente de sismomètres sur les glissements de terrain a révélé une variété de signaux sismiques de magnitude (ML $<$ 1) soupçonnée d'être générée par la déformation de la pente (chute, basculement, glissement, écoulement). Cette sismicité endogène doit être catégorisée. Une classification standard des sources sismiques endogènes est ainsi proposée ; l'objectif de cette norme est de pouvoir comparer l'activité sismique de plusieurs glissements de terrain et d'identifier les mécanismes générant ces signaux sismiques ainsi que leur corrélation avec les forçages externes. Plusieurs propriétés de signal (durée, contenu spectral et forme de spectrogramme) sont prises en compte pour décrire les différentes classes de signaux et permettre une comparaison générique. Les observations montrent que des signaux similaires enregistrés sur différents sites présentent les mêmes propriétés et les sources sismiques possibles sont discutées compte tenu du type de déformation observé sur les pentes étudiées. [...] / This research project aims at increasing knowledge on the mechanisms controlling the deformation of clayey landslides through the combination of passive seismic and geodetic monitoring. Recent studies have demonstrated that seismic monitoring is able to give interesting information on landslide mechanics and in some case to provide precursory patterns useful for failure forecasting. The recent installation of seismometers on landslides revealed a variety of seismic signals of law magnitude (ML $<$ 1) suspected to be generated by slope deformation (falling, toppling, sliding, flowing), weathering of the slope material or fluid circulation. This endogenous seismicity needs to be categorized. We thus proposed a standard classification of the endogenous seismic sources; the objective of this standard is to be able to compare the seismic activity of several landslides and identify the mechanisms generating these seismic signals as well as their correlation with external forcing. Several signal properties (i.e. duration, spectral content and spectrogram shape) are taken into account to describe the different class of signals and allow generic comparison. We observe that similar signals recorded at different sites present the same properties and discussed the possible seismic sources considering the type of deformation observed on the studied slopes. [...]

by Wong, Tak-yee Tammy. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 170-178). / ABSTRACT --- p.i-iii / ACKNOWLEDGEMENTS --- p.iv-v / TABLE OF CONTENTS --- p.vi-x / LIST OF FIGURES --- p.xi-xii - / LIST OF PLATES --- p.xiii-ix / LIST OF TABLES --- p.x-xii / Chapter CHAPTER I: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research Questions --- p.5 / Chapter 1.3 --- Study Significance --- p.7 / Chapter 1.4 --- Organization of the Thesis --- p.8 / Chapter CHAPTER II: --- LITERATURE REVIEW --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Nature of Landslides --- p.10 / Chapter 2.2.1 --- Landslide Classification --- p.10 / Chapter 2.2.2 --- Morphometry of Landslides --- p.12 / Chapter 2.2.3 --- Factors Affecting Landslide Occurrence --- p.16 / Chapter 2.2.3.1 --- Gradient --- p.19 / Chapter 2.2.3.2 --- Slope Shape --- p.21 / Chapter 2.2.3.3 --- Aspect --- p.22 / Chapter 2.2.3.4 --- Vegetation --- p.24 / Chapter 2.2.3.5 --- Drainage --- p.26 / Chapter 2.2.3.6 --- Precipitation/Seismicity --- p.26 / Chapter 2.2.3.7 --- Lithology and Geological Influences --- p.28 / Chapter 2.2.3.8 --- Regolith --- p.29 / Chapter 2.2.3.8.1 --- Hydrological Properties of Soils --- p.29 / Chapter 2.2.3.8.2 --- Engineering Properties of Soils --- p.30 / Chapter 2.3 --- Data Sources for Landslide Studies --- p.31 / Chapter 2.3.1 --- Aerial Photo Interpretation (API) --- p.32 / Chapter 2.3.2 --- Remote Sensing --- p.34 / Chapter 2.3.3 --- Field Survey --- p.35 / Chapter 2.3.4 --- Subsurface Investigation --- p.36 / Chapter 2.4 --- Landslide Studies in Hong Kong --- p.36 / Chapter 2.5 --- Applications of GIS on Landslide Studies --- p.38 / Chapter 2.5.1 --- Major Data in GIS for Landslide Studies --- p.39 / Chapter 2.5.1.1 --- Triangulated Irregular Network (TIN) as a Representation of Surface --- p.39 / Chapter 2.5.2 --- Applications --- p.42 / Chapter 2.5.2.1 --- Inventory --- p.43 / Chapter 2.5.2.2 --- Landslide Hazard Assessment --- p.43 / Chapter 2.5.2.2.1 --- Statistical Modeling --- p.46 / Chapter 2.5.2.2.2 --- Physical Processes or Three- Dimensional Modeling --- p.50 / Chapter 2.6 --- Suggestions for Future Research Directions --- p.51 / Chapter CHAPTER III: --- STUDY AREA --- p.54 / Chapter 3.1 --- Location and Choice of Study Area --- p.54 / Chapter 3.2 --- Climatic Aspects --- p.56 / Chapter 3.3 --- Geological Aspects --- p.62 / Chapter 3.3.1 --- General Information of GASP V --- p.62 / Chapter 3.3.2 --- Rock Types Specific to the Two Sites Chosen --- p.63 / Chapter 3.3.2.1 --- Volcanic Units - Repulse Bay Formation --- p.65 / Chapter 3.3.2.2 --- Sedimentary Units - Port Island Formation (PI) --- p.65 / Chapter 3.4 --- Geomorphological Aspects --- p.66 / Chapter 3.4.1 --- General Information of GASP V --- p.66 / Chapter 3.5 --- Erosion and Stability --- p.67 / Chapter 3.6 --- Vegetation --- p.67 / Chapter 3.7 --- Summary --- p.70 / Chapter CHAPTER IV: --- DATABASE CONSTRUCTION AND MANIPULATION --- p.71 / Chapter 4.1 --- Data Collection --- p.73 / Chapter 4.1.1 --- Aerial Photo Interpretation (API) --- p.73 / Chapter 4.1.1.1 --- Landslip Inventory --- p.75 / Chapter 4.1.2 --- Field Techniques --- p.78 / Chapter 4.1.2.1 --- Slope Failure/Deposit Field Survey sheet --- p.78 / Chapter 4.1.2.2 --- Collection of Landslide Data --- p.79 / Chapter 4.1.3 --- Collection of Existing Data --- p.80 / Chapter 4.1.3.1 --- 1:5000 Topographic Maps --- p.80 / Chapter 4.1.3.2 --- Terrain Classification --- p.81 / Chapter 4.1.3.3 --- WWF Vegetation Database --- p.85 / Chapter 4.2 --- Data Input and Conversion --- p.86 / Chapter 4.2.1 --- Digitizing of Data --- p.87 / Chapter 4.2.1.1 --- Landslip Capture in Stereocord --- p.87 / Chapter 4.2.1.2 --- Data Conversion --- p.94 / Chapter 4.2.1.2.1 --- Topographic Maps - Scanning and Vectorization --- p.94 / Chapter 4.3 --- Data Editing --- p.94 / Chapter 4.3.1 --- Line Cleaning for Landslide Coverage --- p.96 / Chapter 4.3.2 --- Line Cleaning and Height Tagging for Topographic Map --- p.96 / Chapter 4.3.3 --- Editing on Terrain Classification Map --- p.97 / Chapter 4.4 --- Database Construction --- p.97 / Chapter 4.4.1 --- Data Base Design --- p.97 / Chapter 4.4.1.1 --- Graphical Data Base --- p.98 / Chapter 4.4.1.2 --- Attribute Data Base --- p.99 / Chapter 4.4.2 --- Creation of a Triangulated Irregular Network (TIN) --- p.104 / Chapter 4.5 --- Data Preparation and Pre-analysis Manipulation --- p.105 / Chapter 4.5.1 --- Extraction of Terrain Variables from TIN --- p.105 / Chapter 4.5.1.1 --- TIN'S Derived Variable - Elevation --- p.105 / Chapter 4.5.1.2 --- TIN'S Derived Variable - Gradient --- p.107 / Chapter 4.5.1.3 --- TIN'S Derived Variable - Orientation --- p.109 / Chapter 4.5.1.4 --- TIN's Derived Variable - Dimensions (surface distance) of Landslides --- p.109 / Chapter 4.5.1.5 --- Micro-DEM and Profile --- p.109 / Chapter 4.5.1.6 --- Weighting Method Adopted in Calculating the Gradient and Orientation of Primary Depletion Scar --- p.110 / Chapter 4.5.2 --- Data Preprocessing --- p.110 / Chapter 4.6 --- Summary --- p.114 / Chapter CHAPTER V: --- STATISTICAL ANALYSIS OF LANDSLIDE DISTRIBUTION --- p.115 / Chapter 5.1 --- Sampling --- p.116 / Chapter 5.1.1 --- Sampling Frame --- p.116 / Chapter 5.1.1.1 --- Simple Random Point Sampling --- p.117 / Chapter 5.1.1.2 --- Stratified Random Point Sampling --- p.117 / Chapter 5.2 --- Comparison of the Two Study Areas --- p.119 / Chapter 5.3 --- Statistical Analyses of Landslip Variables --- p.123 / Chapter 5.3.1 --- Gradient (TIN) and Elevation --- p.124 / Chapter 5.3.2 --- "Aspect, Geological Materials, Gradient, Terrain Component, Erosion & Instability, and Vegetation" --- p.126 / Chapter 5.3.2.1 --- Aspect --- p.127 / Chapter 5.3.2.2 --- Geological Materials --- p.130 / Chapter 5.3.2.3 --- Gradient --- p.132 / Chapter 5.3.2.4 --- Terrain Component --- p.137 / Chapter 5.3.2.5 --- Erosion and Instability --- p.140 / Chapter 5.3.2.6 --- WWF Vegetation --- p.140 / Chapter 5.3.3 --- Result of the Partial Model --- p.145 / Chapter 5.4 --- Logistic Regression Model --- p.147 / Chapter 5.4.1 --- Landslide Probability Mapping --- p.154 / Chapter 5.4.2 --- Testing the Model Output --- p.157 / Chapter 5.5 --- Summary --- p.161 / Chapter CHAPTER VI: --- CONCLUSIONS --- p.162 / Chapter 6.1 --- Summary of Findings --- p.162 / Chapter 6.2 --- Limitations of the Study --- p.163 / Chapter 6.3 --- Recommendations for Further Studies --- p.166 / BIBLOGRAPHY --- p.167 / APPENDICES / "APPENDIX I Draft 3.3 slope failure/deposit field survey sheet (King, 1994a)" / "APPENDIX II Landslide/deposit field description sheet (King, 1994b)" / "APPENDIX III Hourly rainfall (mm) record at N05 in September 26-27，1993 (Source: Special Projects Division, Geotechnical Engineering Office, Civil Engineering Department)" / "APPENDIX IV Hourly rainfall (mm) record at R23 in September 1993 (Source: Hydrometeorology Section, Royal Observatory, Hong Kong,1993)" / "APPENDIX V Hourly rainfall (mm) record at R31 in September 1993 (Source: Hydrometeorology Section, Royal Observatory, Hong Kong,1993)"

[néant] / [néant]

The scarcity of data poses a challenging obstacle for the study of natural disasters, especially in developing countries where the social vulnerability plays as important a role as the physical vulnerability.  The work presented in this thesis is oriented towards the demonstration of the usefulness of press archives as a data source for the temporal and spatial analysis of landslides in Tegucigalpa, Honduras for the period between 1980 and 2005.  In the last four decades, Tegucigalpa has been characterized by a disorganized urban growth that has significantly contributed to the destabilization of the city’s slopes.  In the first part of the thesis, a description of the database compilation procedure is provided.  The limitations of using data derived from press archives have also been addressed to indicate how these affect the subsequent landslide analyses.  In the second part, the temporal richness offered by press archives has allowed the establishment of rainfall thresholds for landslide occurrence.  Through the use of the critical rainfall intensity method, the analysis of rainfall thresholds for 7, 15, 30 and 60 antecedent days shows that the number of yielded false alarms increases with the threshold duration.  A new method based on the rainfall frequency contour lines was proposed to improve the distinction between days with and without landslides.  This method also offers the possibility to identify the landslides that may only occur with a major contribution of anthropogenic disturbances as well as those landslides induced by high-magnitude rainfall events.  In the third part, the matrix method has been employed to construct two landslide susceptibility maps: one based on the multi-temporal press-based landslide inventory and a second one based on the landslide inventory derived from an aerial photograph interpretation carried out in 2014.  Despite the low spatial accuracy provided by the press archives in locating the landslides, both maps exhibit 69% of consistency in the susceptibility classes and a good agreement in the areas with the highest propensity to landslides.  Finally, the integration of these studies with major actions required to improve the process of landslide data collection is proposed to prepare Tegucigalpa for future landslides.

abstract: I investigate the Black Canyon City landslide (BCC landslide), a prominent deep-seated landslide located northeast of Black Canyon City, Arizona. Although the landslide does not appear to pose a significant hazard to structures, its prominent features and high topographic relief make it an excellent site to study the geologic setting under which such features develop. This study has the potential to contribute toward understanding the landscape evolution in similar geologic and topographic settings, and for characterizing the underlying structural processes of this deep-seated feature. We use field and remotely-based surface geology and geomorphological mapping to characterize the landslide geometry and its surface displacement. We use the Structure from Motion (SfM) method to generate a 0.2 m resolution digital elevation model and rectified ortho-photo imagery from unmanned aerial vehicle (UAV) - and balloon-based images and used them as the base map for our mapping. The ~0.6 km2 landslide is easily identified through remotely-sensed imagery and in the field because of the prominent east-west trending fractures defining its upper extensional portion. The landslide displaces a series of Early and Middle Miocene volcanic and sedimentary rocks. The main head scarp is ~600 m long and oriented E-W with some NW-SE oriented minor scarps. Numerous fractures varying from millimeters to meters in opening were identified throughout the landslide body (mostly with longitudinal orientation). The occurrence of a distinctive layer of dark reddish basalt presents a key displaced marker to estimate the long-term deformation of the slide mass. Using this marker, the total vertical displacement is estimated to be ~70 m, with maximum movement of ~95 m to the SE. This study indicates that the landslide motion is translational with a slight rotational character. We estimate the rate of the slide motion by resurvey of monuments on and off the slide, and examination of disturbed vegetation located along the fractures. The analysis indicates a slow integrated average landslide velocity of 10-60 mm/yr. The slide motion is probably driven during annual wet periods when increased saturation of the slide mass weakens the basal slip surface and the overall mass of the slide is increased. Results from our study suggest that the slide is stable and does not pose significant hazard for the surrounding area given no extreme changes in the environmental condition. Although the landslide is categorized as very slow (according to Cruden and Varnes, 1996), monitoring the landslide is still necessary. / Dissertation/Thesis / Masters Thesis Geological Sciences 2016