Showing papers by "Jacques Locat published in 2007"

New insight techniques to analyze rock-slope relief using DEM and 3D-imaging cloud points: COLTOP-3D software

Abstract: COLTOP-3D software performs structural analysis of a topography using a digital elevation model (DEM). A color is defined based on slope aspect and slope angle in order to obtain a unique color code for each spatial orientation. Thus continuous planar structures appear as a unique color. Several tools are included to create stereonet(s), to draw traces of discontinuities, or to compute automatically density stereonet. A new version has recently been developed to represent true 3D surfaces from point clouds. Examples are shown to demonstrate the efficiency of the method. High resolution DEMs acquired with Lidar techniques greatly improve topographic analyses.

Submarine mass movements and their consequences : 3rd international symposium

Abstract: Role of submarine slides in margin development.- Fractal statistics of the Storegga Slide.- Submarine Paleo-Failure Morphology On A Glaciated Continental Margin From 3d Seismic Data.- Slope Instability And Mass Transport Deposits On The Godavari River Delta, East Indian Margin From A Regional Geological Perspective.- Repeated Instability Of The Nw African Margin Related To Buried Landslide Scarps.- Along Slope Variations In Mass Failures And Relationships To Major Plio-Pleistocene Morphological Elements, Sw Labrador Sea.- Submarine Landslides Along The North Ecuador - South Colombia Convergent Margin: Possible Tectonic Control.- The Southern Flank Of The Storegga Slide: Imaging And Geomorphological Analyses Using 3d Seismic.- Submarine Mass Movements On An Active Fault System In The Central Gulf Of Corinth.- Analysis Of Multibeam Seafloor Imagery Of The Laurentian Fan And The 1929 Grand Banks Landslide Area.- Landslide And Gravity Flow Features And Processes Of The Nazare And Setubal Canyons, West Iberian Margin.- Mass waste evolution: From slump to distal turbidites.- Experimental Studies Of Subaqueous Vs. Subaerial Debris Flows - Velocity Characteristics As A function Of The Ambient Fluid.- The General Behavior Of Mass Gravity Flows In The Marine Environment.- Submarine Spreading: Dynamics And Development.- Flood-Induced Turbidites From Northern Hudson Bay And Western Hudson Strait: A Two-Pulse Record Of Lake Agassiz Final Outburst Flood?.- Underwater Rockfall Kinematics: A Preliminary Analysis.- Anthropogenic Turbidity Current Deposits In A Seismically Active Graben, The Gulf Of Corinth, Greece: A Useful Tool For Studying Turbidity Current Transport Processes.- New techniques, approaches and challenges in submarine slope instability analysis.- Probability Study On Submarine Slope Stability.- Marine Deep-Water Free-Fall Cpt Measurements For Landslide Characterisation Off Crete, Greece (Eastern Mediterranean Sea) Part 1: A New 4000M Cone Penetrometer.- Monitoring stress on submarine slopes and sediment physical properties.- Linking Geotechnical And Rheological Properties From Failure To Post-Failure: The Pointe-Du-Fort Slide, Saguenay Fjord, Quebec.- Rheological Properties Of Fine-Grained Sediments In Modeling Submarine Mass Movements: The Role Of Texture.- Marine Deep-Water Free-Fall Cpt Measurements For Landslide Characterisation Off Crete, Greece (Eastern Mediterranean Sea) Part 2: Initial Data From The Western Cretan Sea.- Recursive Failure Of The Gulf Of Mexico Continental Slope: Timing And Causes.- Geotechnical Considerations Of Submarine Canyon Formation: The Case Of Cap De Creus Canyon.- Submarine slides in coastal areas, semienclosed seas (fjords,estuaries, gulfs) and lakes.- Submarine Mass Movements In The Betsiamites Area, Lower St. Lawrence Estuary, Quebec, Canada.- Submerged Landslide Morphologies In The Albano Lake (Rome, Italy).- Dynamics Of The Deltaic Canyon Area Of The Rv. Chorokhi, Georgia.- The 1990 Submarine Slide Outside The Nidelv River Mouth, Trondheim, Norway.- Submarine Slope Failures Near Seward, Alaska, During The M9.2 1964 Earthquake.- The Ad 1881 Earthquake-Triggered Slump And Late Holocene Flood-Induced Turbidites From Proglacial Lake Bramant, Western French Alps.- Morphosedimentology Of Submarine Mass-Movements And Gravity Flows Offshore Sept-Iles, Nw Gulf Of St. Lawrence (Quebec, Canada).- Sediment Failure Processes In Active Grabens: The Western Gulf Of Corinth (Greece).- Submarine landslides in volcanic island settings.- High Frequency Sediment Failures In A Submarine Volcanic Environment: The Santorini (Thera) Basin In The Aegean Sea.- Sediment Stability Conditions West Of Milos Island, West Hellenic Volcanic Arc.- Submarine mass movements and tsunamis.- Mass Wasting Processes - Offshore Sumatra.- Slope Failures Of The Flanks Of The Southern Cape Verde Islands.- Triggering Factors And Tsunamigenic Potential Of A Large Submarine Mass Failure On The Western Nile Margin (Rosetta Area, Egypt).- Reassessment Of Seismically Induced, Tsunamigenic Submarine Slope Failures In Port Valdez, Alaska, USA.- Towards The Mitigation Of The Tsunami Risk By Submarine Mass Failures In The Gulf Of Corinth: The Xylocastro Resort Town Case Study.- Probabilistic Smf Tsunami Hazard Assessment For The Upper East Coast Of The United States.- Role Of Soil Behavior On The Initial Kinematics Of Tsunamigenic Slides.- Revisiting Submarine Mass Movements Along The U.S. Atlantic Continental Margin: Implications For Tsunami Hazards.- Tsunamigenic Landslides In The Western Corinth Gulf: Numerical Scenarios.- Tsunamis Generated By Coastal And Submarine Landslides In The Mediterranean Sea.

Morphosedimentology Of Submarine Mass-Movements And Gravity Flows Offshore Sept-Îles, Nw Gulf Of St. Lawrence (Québec, Canada)

Abstract: Recent multibeam sonar and acoustic subbottom profiler surveys and sediment coring offshore the city of Sept-Iles (NW Gulf of St. Lawrence) reveal different types of submarine mass-movements and gravity flows in glaciomarine, paraglacial and postglacial deposits. These mass-movement and gravity flow features are slumps, gullies and channel-levee systems and fans. The key results of this study include: 1) slumps involve the entire deglacial and postglacial sequence, indicating their recent triggering; 2) identification of a 57-cm thick turbidite and several sand layers in sediment cores collected in a deep and isolated basin unaffected by fluvial inputs, along with 210 Pb measurements, indicate the recent activity of mass wasting events derived from slope instabilities; 3) important volumes of sediments are being transported from the coastal to the deeper marine environment by gravity flows processes on the prodelta of the Moisie River. Hypotheses for explaining the widespread occurrence of recent mass-movements due to slope instabilities in the area possibly include their possible triggering by the AD 1663 (M~7) or another large earthquake.

Scientific ocean drilling behind the assessment of geo‐hazards from submarine slides, Barcelona, Spain, 25–27 October 2006

Abstract: Submarine slope instability represents a geo-hazard for its destructive potential on nearshore structures and life and offshore seabed structures. Submarine slides may bear a tsunamigenic potential and are capable of methane gas release into the seawater and atmosphere. A recent workshop sponsored by the European Science Foundation (ESF; http://www.esf.org), “Scientific Ocean Drilling Behind the Assessment of Geo-hazards From Submarine Slides,” held in Barcelona, Spain, 25–27 October 2006, reviewed the current state of knowledge on submarine slope failures and how scientific drilling can improve our knowledge of the process and help to mitigate the derived risks (a report with full details of participants and program can be found at http://www.geohazards.no/IGCP511/). The workshop gathered 50 scientists and representatives of private companies, mainly from the European area, representing a wide spectrum of disciplines such as geophysics, stratigraphy sedimentology paleoceanography marine geotechnology, geotechnical engineering, and tsunami modeling. During the workshop, it was agreed that scientific drilling offers the possibility of answering a number of scientific questions, among them, (1) What is the frequency of submarine slides? (2) What was the tsunamigenic potential of past submarine slides, and what is the tsunamigenic potential of unfailed submarine slopes? (3) Do precursory phenomena of slope failure exist? (4) Can we monitor sea-floor gravitational movements such as creep? (5) What makes up weak layers in midlatitude continental margins? And (6) when and under what circumstances do weak layers form? Scientific drilling also offers the possibility of testing at least two existing hypotheses on basic mechanisms of submarine slide generation and of massive releases of gas: (1) focusing of fluids and lateral transfer of stresses under variable overburden on permeable layers and (2) proving the link between methane emissions during rapid climatic changes and submarine slides.

Rheological Properties Of Fine-Grained Sediments In Modeling Submarine Mass Movements: The Role Of Texture

Abstract: The rheological behavior of soils depends on many factors, including their mineralogy and grain size distribution. This work comprises an extensive search of data collected from the literature, an experimental work on about 17 samples. These results, along with a compilation of existing data, have been used to show that, as a first approximation, the yield strength/viscosity ratio is about 1000, 100 and less than 10 for clayey, silty and sandy fine-grained sediments mixtures, respectively. Our research results on the rheological properties of fine-grained sediments indicate that they are very sensitive to the variation in grain size, shear rate, and geometry of the system.

Linking Geotechnical And Rheological Properties From Failure To Post-Failure: The Pointe-Du-Fort Slide, Saguenay Fjord, Québec

Abstract: The Pointe-du-Fort submarine mass movement likely took place at the time of the with a run out distance of 1070m and a final flow thickness of 10-15m resting on a slope of 1.4 degrees. The slide involved about 1.95 Mm 3 of clayey sediments from an original slope of 24 degrees. The slide took place in normally consolidated sediments composed of stratified low organic Laflamme Sea clay at the base overlain by progressively more organic rich recent sediments. In situ strength testing and sampling on the tidal flat, morphological analysis and remolded strength of the debris lobe can be related to rheological tests to model the mobility of the debris. For the first time, it has been possible to link the mobility of a submarine slide with the characteristics of the sediments at the time of failure with no need to consider water content increase to explain the observed mobility.

Notes sur la minéralogie des sédiments fins du lac Ojibway, en particulier ceux de la région de Matagami, Québec

Abstract: La mineralogie des sediments fins glacio-lacustres du lac Ojibway est revue et commentee a partir d'un certain nombre d'analyses recentes. On constate que la mineralogie de la fraction argileuse est dominee par les mineraux felsiques tels que le feldspath et le quartz. L'illite et la chlorite predominent parmi les phyllosilicates qui comprennent aussi des mineraux interstratifies et des traces de vermiculite. La predominance des mineraux felsiques dans la fraction argileuse traduit le caractere detritique de ces sediments d'origine glaciaire. En outre, des donnees tirees des analyses chimiques totales et des amorphes sont aussi compilees. Deux mineraux peuvent etre utilises comme traceurs mineralogiques: la kaolinite et les carbonates. La teneur en carbonates des sediments est mis en correlation avec les episodes glaciaires du Nouveau-Quebec et les recurrences de Cochrane I et II. L'etude en microscopie electronique a revele l'existence d'une structure floculee dans la fraction fine. Les carbonates et le calcium, en particulier, seraient responsables du type de microstructure observee dans les sediments : le calcium comme agent de floculation et les carbonates comme ciment entre les particules.

Stratigraphie du Quaternaire et phoque fossile, région de la Durantaye, Québec

Abstract: Le squelette presque complet d'un phoque fossile a ete decouvert pres de La Durantaye, Quebec, dans des sediments marins associes a la submersion de la mer de Goldthwait. Une identification preliminaire a revele qu'il s'agit d'un phoque gris ou d'un phoque a capuchon. Le cadre stratigraphique de la region a ete precise. De la base au sommet les unites suivantes se succedent: 1) des sables et graviers grossiers (5 m) ; 2) des rythmites de type distal (2 m) ; 3) un till rougeâtre argileux tres compact (1 a 2 m) ; 4) des sables et graviers fins biens lites (2 m) ; 5) des rythmites de type proximal (2 m) ; 6) un diamicton glacio-marin a Balanus hameh (2 m) ; 7) une argile silteuse parfois tres noire (ou fut trouve le phoque fossile) (3 m) ; 8) des silts sableux tres fossiliferes contenant parfois des blocs (5 m) ; 9) une argile grise massive (jusqu'a 50 m) ; 10) des sables et graviers littoraux (1 m) ; 11) des sediments fluviatiles recents (1 m). Les rythmites preglaciaires et postglaciaires sont associees respectivement aux varves de Beaupre et aux sediments varves de la riviere Chaudiere. L'extension vers l'est de la moraine de Breakeyville est egalement proposee. Enfin, les silts sableux marqueraient un abaissement du niveau marin caracterise par une activite glacielle pendant l'episode marin.

Caractéristiques des conditions benthiques existant dans la partie amont du fjord du Saguenay (Québec, Canada)

Abstract: Mots-cles : fjord du Saguenay, sediments benthiques, tomodensitometre axial. Abstract: In 1996, following torrential rains, a layer of clean sediments was deposited in the upstream part of the Saguenay Fjord. This layer acted as a damping layer between contaminated sediments and the Saguenay waters. It is important to collect information on the water-sediments interface, which is the site of exchanges between the sedi- ments and the waters. Three oceanographical campaigns have allowed us to obtain the data on the velocity of the benthic currents and the properties of the surface sediments. The velocities have been obtained by means of two cur- rent meters located at 3 m from the bottom and by means of registered videos. These two types of measurements have given comparable results. The main information collected on the sediments were their water content, grain size, density, and the presence of benthic fauna. The distribution of the main biogenic structure, the tubes of polychetes, is related to the depth of the site and to the grain size of the sediments. For the surface layer, large variations of the water content were obtained during the field measurements. Tests with an axial tomodensitometer have revealed a large variation in the density of the sediments in the top 2.5 cm.