1,721,044 research outputs found
Landslide Dams in the Central Andes of Argentina (Northern Patagonia and the Argentine Northwest)
No full textLandslide dams are frequent phenomena in the Argentine Andes. We studied 20 landslide dams in NW Argentina and 41 landslide dams in northern Patagonia. These examples show that most of the landslide dams in both regions have longevity of several hundred to several tens of thousands of years. In those cases where the mode of dam erosion/breach was reconstructable it was either related to climatic variability influencing the inflow of water into the landslide-dammed lake or by landsliding into the landslide dammed lake causing a tsunami wave which overtopped the dam crown and caused its erosion. However such tsunami waves not always lead to dam failure. There is one case where flood deposits downriver a dam exist and the landslide dammed lake contains a voluminous landslide deposit, however the dam did not breach. Hence the flood deposits are related to the tsunami wave but not to a breach. In addition, our examples indicate the necessity of expanding the well established dam classification system used globally in the past 18 years. Here we define 4 further dam types which are related to (a) the diversion of the river away from the valley over bedrock (b) the diversion of the river into the neighbouring catchments (c) the deposition of the landslide in a drainage divide, and (d) the formation of multiple dams by the breach of a landslide dam itself. Furthermore, ponds on top of landslide deposits are frequent and depending on their size a catastrophic release may cause damage.Fil: Hermanns, Reginald L.. Norwegian University of Science and Technology; NoruegaFil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Fauque, Luis Enrique. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; ArgentinaFil: Niedermann, Samuel. GeoForschungsZentrum; Alemani
Revisión de la Estratigrafía Glaciaria de la Cuenca del Río Mendoza
Full text linkEste trabajo formó parte del XIX Congreso Geológico Argentino, realizado en Córdoba entre el 2 y el 6 de Junio de 2014, y auspiciado por la Asociación Geológica Argentina. Es parte de la sección Geología del Cuaternario, Geomorfología y Cambio Climático.Fil: Fauqué, Luis A. Ministerio de Energía y Minería. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Hermanns, Reginald L. Geological Survey of Norway (NGU); Dinamarca.Fil: Wilson, Carlos. Ministerio de Energía y Minería. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Rosas, Mario. Ministerio de Energía y Minería. Servicio Geológico Minero Argentino. Delegación Mendoza; Argentina.Fil: Tedesco, Ana M. Ministerio de Energía y Minería. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Miranda, Fernando. Ministerio de Energía y Minería. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina
Quaternary tephrochronology helps define conditioning factors and triggering mechanisms of rock avalanches in NW Argentina
No full textNatural dams in the headwater of the Lileo valley (Neuquén province, Argentina)
Full text linkEn este trabajo analizamos tres endicamientos naturales por depositación de movimientos en masa que tuvieron lugar en las nacientes del arroyo Lileo (Cordillera de los Andes, norte neuquino), dos de ellos ocurrieron en los últimos 50 años. El primero ocurrió en el Holoceno, por desprendimiento de 0,14 km3 de volcanitas en la ladera oeste del valle, cerca de las nacientes del arroyo La Tregua. Este bloqueo originó una laguna permanente de 0,44 km2. En los años '60, la depositación de una avalancha de detritos originada en la ladera opuesta del valle, frente a la escarpa de la avalancha de rocas, ocluyó la brecha labrada por erosión fluvial en el depósito de avalancha de rocas, generando un segundo cuerpo lacustre de tipo efímero. El último endicamiento, que tuvo lugar entre >1962-1962- < 1985, was caused by a sudden progradation of a conoid developed in the mouth of La Tregua creek, due to an important contribution of material by a debris flow originated in the same zone of detachment as the aforementioned case. The continuous deposition of material in the conoid zone has buried the poles of the Loma de la Lata - Talcahuano gas pipeline, built in 1998. As the zone of detachment of the eastern side of La Tregua valley shows signs of instability, we consider it is possible that a new mass movement may cause another dam.Fil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Hermanns, Reginald L.. Geological Survey; NoruegaFil: González, María Paz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentin
Integrated analysis of past, and potential future rock slope failures of various size from Rombakstøtta, Nordland
Full text linkCatastrophic failure of large rock slopes has led to fatalities in Norwegian settlements several times per century. The Geological Survey of Norway (NGU) currently carry out systematic geological mapping of potentially unstable rock slopes in Norway, on assignment from the Norwegian Water Resources and Energy Directorate (NVE). In this context, a hazard analysis and preliminary consequence assessment of the unstable rock slope at Rombakstøtta in Narvik kommune, Nordland fylke has been carried out. In addition, an analysis of rock fall run-out lengths and frequencies since deglaciation has been carried out in the modelling software Rockyfor3D. A fragmentation cycle analysis, used to assess the fragmentation during a failure and to separate rock fall deposits from rock avalanche deposits, has been developed and tested.
The study area is located in a north facing slope along a fjord ca. seven kilometers east of the city Narvik. Based on delimiting lineaments observed in the field, aerial photos, photo panoramas and digital elevation models, eight failure scenarios (1.A-B, 2.A, 3.A and 4.A-D) are defined at Rombakstøtta. Application of NGU´s hazard analysis resulted in one scenario being assigned to the medium/low hazard class, six to the medium hazard class, and one to the high hazard class. Volume estimation and run-out analysis were carried out for all scenarios as a part of the preliminary consequence assessment. Resulting volumes for the scenarios range from 10 000 m3 to 4 650 000 m3, and four of the scenarios have modelled run-out reaching houses, Ofotbanen, the E6 highway, and the fjord. An additional two scenarios have run-out reaching Ofotbanen.
The rock fall analysis show that rock fall blocks larger than ~7.8 m3 have reached coarse rock avalanche deposits with a possible frequency of 5-13 blocks per 1x1 m since deglaciation. This could affect cosmogenic nuclide dating of rock avalanche deposits, carried out within the CryoWALL project to which this thesis has affiliations. The calculation is based on rock fall modelling and an extrapolation of a dataset with ~100 years of rock fall registrations.
The fragmentation cycle analysis has been developed and applied inspired by Charrière et al. (2016). Results suggest that rock avalanche deposits at Rombakstøtta underwent 0-3 fragmentation cycles during failure. And that rock fall deposits below Rombakstøtta generally experienced more than 4 fragmentation cycles during failure. Results are discussed and compared to the results of Charrière et al. (2016) from the Frank Slide, Canada
Integrated analysis of past, and potential future rock slope failures of various size from Rombakstøtta, Nordland
No full textCatastrophic failure of large rock slopes has led to fatalities in Norwegian settlements several times per century. The Geological Survey of Norway (NGU) currently carry out systematic geological mapping of potentially unstable rock slopes in Norway, on assignment from the Norwegian Water Resources and Energy Directorate (NVE). In this context, a hazard analysis and preliminary consequence assessment of the unstable rock slope at Rombakstøtta in Narvik kommune, Nordland fylke has been carried out. In addition, an analysis of rock fall run-out lengths and frequencies since deglaciation has been carried out in the modelling software Rockyfor3D. A fragmentation cycle analysis, used to assess the fragmentation during a failure and to separate rock fall deposits from rock avalanche deposits, has been developed and tested.
The study area is located in a north facing slope along a fjord ca. seven kilometers east of the city Narvik. Based on delimiting lineaments observed in the field, aerial photos, photo panoramas and digital elevation models, eight failure scenarios (1.A-B, 2.A, 3.A and 4.A-D) are defined at Rombakstøtta. Application of NGU´s hazard analysis resulted in one scenario being assigned to the medium/low hazard class, six to the medium hazard class, and one to the high hazard class. Volume estimation and run-out analysis were carried out for all scenarios as a part of the preliminary consequence assessment. Resulting volumes for the scenarios range from 10 000 m3 to 4 650 000 m3, and four of the scenarios have modelled run-out reaching houses, Ofotbanen, the E6 highway, and the fjord. An additional two scenarios have run-out reaching Ofotbanen.
The rock fall analysis show that rock fall blocks larger than ~7.8 m3 have reached coarse rock avalanche deposits with a possible frequency of 5-13 blocks per 1x1 m since deglaciation. This could affect cosmogenic nuclide dating of rock avalanche deposits, carried out within the CryoWALL project to which this thesis has affiliations. The calculation is based on rock fall modelling and an extrapolation of a dataset with ~100 years of rock fall registrations.
The fragmentation cycle analysis has been developed and applied inspired by Charrière et al. (2016). Results suggest that rock avalanche deposits at Rombakstøtta underwent 0-3 fragmentation cycles during failure. And that rock fall deposits below Rombakstøtta generally experienced more than 4 fragmentation cycles during failure. Results are discussed and compared to the results of Charrière et al. (2016) from the Frank Slide, Canada
Analysis of the Prestura Rock Slope Failure and Quaternary mapping of Lake Tinnsjø, Telemark
No full textThis thesis covers an analysis of the Prestura rockslope failure and quaternary mapping of lake Tinnsjø. The analysis of the Prestura rockslope failure involves a structural analysis, kinematic analysis, volume calculations, empirical run-out analysis and semi-empirical displacement wave analysis.
Five different joint sets are identified close to the Prestura failure area by systematic field mapping, confirmed by structural analysis of terrestrial laser scan (TLS) data. The structural data achieved form field mapping were included in the kinematic analysis. The kinematic analysis shows that planar sliding, wedge sliding and direct toppling is feasible at steep slopes dipping over 60°. Thus, only considered as feasible failure modes for small rock volumes. Large scale rock slope failure was only considered feasible by a combination of the over 60° NE dipping exfoliation joint set (J1) and the less than 20° NE dipping foliation (SF), making the complex bi-planar sliding a feasible failure mode.
The volume of the potential failed rock masses is estimated to be 3 9 million m3. The volume of the displaced masses was estimated to be 2 3 million m3. The difference in volume suggest at least one pre-deglaciation event from the same source that deposited onto the glacier. The volume vs. run-out correlation of Prestura is considered similar to the Randa rockslide (Sartori et al., 2003) classifying the failure of the Prestura rockslope as a rockslide, where the failure lasted over several hours. The semi-empirical displacement wave analysis indicate that Prestura created displacement waves when it failed, however the rockslide is now considered dormant. Thus, this site does not present a high hazard at present.
The structural data and geomorphology of the Prestura rockslide has been compared to the Håkåneset rockslope, in order to understand why the Prestura rockslide failed catastrophically while the Håkåneset rockslope has deformed with low rates over a long time. The structural condition is identical at both slopes thus the steepness of the slope is the only difference that can be mapped out. While Prestura has an average slope inclination of 46° has Håkåneset an average slope inclination of 38°, hence Prestura has more slope sections with a dip where failure become kinematically feasible. This is supported by a general relief analysis showing that Tinnsjø is narrower and deeper at Prestura than at Håkåneset, suggesting stronger glacial slope oversteepening at that place.
Quaternary mapping, based on 2x2m resolution bathymetrical data, reveal landforms such as deltas with dunes, terraces interpreted as kame terraces, landslide scars, landslide deposits, and dead ice terrain at the lake floor. The most frequent mapped landform are landslide scars, with highest concentration along terraces close to the unstable slope of Håkåneset. This is considered as evidence of long-lasting movement of the Håkåneset rockslope. This is further supported by the presence of longitudinal ridges on the terrace surface. These are interpreted to be caused by the Håkåneset rockslide inducing into the terrace and bulldozing the sediments in front of the slide. Despite the high amount of landslide scars, no landslide deposits were mapped at the basin floor. This can be explained by the presence of high velocity currents at the bottom of lake Tinnsjø that can also trigger turbidity currents at the basin floor. Such turbidity currents are considered a potential hazard because they can break subaquatic cables. A larger risk to society might represent potential landslide triggered tsunamis from large subaquatic slope failures. When comparing the volumes of the largest subaquatic failures in lake Tinnsjø with other failures elsewhere in Norway such failures have caused considerable landslide- triggered tsunamis. However, in order to assess the hazard sediment characteristics that control the velocity of failure would have to be studied which is not part of this thesis
Entrainment potential of rock avalanches in Norway. - Parameter test and case study at the unstable rock slope Børa (Romsdal Valley, western Norway)
No full textRock avalanches are frequently reported to entrain significant volumes of debris on their travel path. However, little is known about the debris entrainment potential in Norway. This thesis aims to evaluate and better understand the debris entrainment potential of Norwegian rock avalanches and to study how the run-out is affected by entrainment of debris. Numerical run-out modelling of the unstable rock slope Børa, Romsdal Valley, western Norway is performed to evaluate the mentioned topics.
A sensitivity analysis is carried out in order to determine reasonable input parameters for numerical run-out modelling in DAN3D and to assess the run-outs sensitivity to the different input parameters. The analyses are carried out on three scenarios of different volumes; Børa C (76 000 m3), Børa C Large (476 000 m3) and Børa B (2 400 000 m3). The Voellmy rheology with friction coefficient µ = 0.15 and turbulence coefficient ξ = 500 m/s2 are considered appropriate parameters for the scenarios at Børa, and are applied as a reference. The run-out is sensitive to the friction coefficient µ and the friction angle φb (frictional model), showing decreasing run-outs for increasing values. In addition, the run-out of the larger volumes are slightly sensitive to changes in the turbulence coefficient ξ. None of the remaining input parameters in DAN3D are found to affect modelled run-out distance.
Scenario Børa C is used for the purpose of assessing the entrainment potential. Entrainment of unsaturated material decreases the run-out distance. However, entrainment of completely unsaturated material is not considered realistic at Børa. The opposite is observed for saturated material, showing increasing run-out for increasing pore pressure. In addition, the run-out is highly sensitive to the input friction angle φb, indicating that the properties of the debris are of great importance when parameters are determined. Further analyses shows that entrainment of material (with pore pressure) from lower parts of the slope provides longer run-outs and larger final volumes compared to entrainment from the upper part.
Entrainment in DAN3D is controlled by a user defined entrainment rate, E. The parameter is difficult to assess. Mainly because the expected final volume is required as input. This is extremely difficult to assess, especially in a forward analysis. At Børa, the modelled final volume does not equal the expected final volume. The results indicate that the input final volume should be increased by a factor of one to obtain expected final volumes when modelling, but further analyses are required to state this. Based on the results of this thesis, it is suggested that perhaps DAN3D will not constitute the best tool when a forward analysis of an entrainment event is to be carried out
Past slope collapse and current unstable slopes along a cliff at Hyllestad Kommune
No full textWith the aim of a complete national database of potential unstable slopes, the Geological Survey of Norway currently carries out systematic geological mapping of rock slopes organized in counties. As part of the survey of Sogn og Fjordane, a hazard and preliminary consequence assessment of a north-facing cliff in Hyllestad municipality has been completed within this thesis.
Two independent inventories were assembled, one on unstable rock slopes along the cliff face, the other on post-glacial rock slope failure deposits. In total 9 unstable slopes were detected, that present a total of 14 failure scenarios. In order to determine the hazard, the Norwegian hazard classification system was used. This comprises in mapping out the limiting structures, defining structural control, and a kinematic feasibility test of failures. In addition, at two sites displacement rates have been measured by dGNSS and extensometers, for the other, these were assessed based on morphological expression of deformation. Rockfall activity was assessed on a 3D photogrammetric model. The resulting hazard classification classified 12 of the scenarios to a medium hazard class, while 2 of the scenarios were classified with low hazard. The preliminary consequence assessment consisted of volume calculations based on delimiting structures and a run-out analysis considering the potential for initiating displacement waves. Of the detected scenarios, 3 have volumes defined that can fail as rock avalanches with excessive travel lengths. A run-out analysis using an empirical relation between volume and angle of reach indicate that the failure of all scenarios will reach the fjord.
The inventory of past events was assessed by bathymetric data from the fjord and digital terrain models on the shore. Deposits were interpreted, and volumes were estimated based on the SLBL-method. Frequencies have been analyzed based on the assumption of a constant frequency distribution since last deglaciation. This is supported by data from other fjords. Volume-Frequency distributions suggested a best fit of an inverse power-law model for volumes above a threshold of 0,020Mm3. Resulting frequency of rock slope failures with volumes ≥ 0,020Mm3 was estimated to 1 / 334 years. The frequency of rock avalanches (≥0,250Mm3) was estimated to 1 / 2879 years.
Based on the hazard classification of unstable slopes and frequencies of past events, the applicability of quantitative hazard probabilities has been discussed due to the need for quantitative limits for the Norwegian regulations on technical requirements for buildings
Infralyddeteksjon av snøskred og vurdering av konsept for automatisk integrasjon med database for snøobservasjoner
Full text linkInfralydsystemene som er installert for overvåking av skredaktivitet i Norge har det kommersielle navnet «Infrasound detection of avalanches», forkortet IDA. I Norge har det tradisjonelt sett vært liten bruk av tekniske løsninger for automatisk deteksjon av skredaktivitet, og før IDA-systemene ble installert i Norge hadde ikke systemet blitt testet i alpine områder der terrenget generelt har lite vegetasjon. Det var derfor både strategiske og tekniske grunner for å teste IDA-systemet i Norge (Humstad, et al., 2016).
Statens vegvesen [SVV] har installert IDA-systemet ved tre lokaliteter; Grasdalen, Indreeidsdalen og Kattfjordeidet. Denne oppgaven fokuserer fortrinnsvis på IDA-systemet på Kattfjordeidet, der det i oppgaven er definert skredsoner og beregnet teoretiske IDA-parametere. Teoretiske IDA-parametere brukes til å knytte IDA-deteksjoner til omkringliggende terreng, siden IDA-systemet kun angir retningen mot skredet og ikke eksakt i hvilken skredbane skredet forekom (Humstad, et al., 2016).
RegObs er Norges vassdrag- og energidirektorats [NVE] database for snøobservasjoner. Observasjonene, i tillegg til meteorologiske data, danner grunnlaget for det regionale snøskredvarselet i Norge. Bruk av deteksjonssystemer i skredvarslingen øker skredvarselets validitet og har tillatt å redusere stengetiden av veier (Steinkogler, et al., 2016). For å gjøre IDA-deteksjoner mer tilgjengelig og brukervennlig for skredvarslerne bør IDA-deteksjonene registreres i regObs.
I denne oppgaven presenteres det et forslag til en automatisk dataflyt fra IDA-systemene til regObs. Forslaget bygger på nøyaktige data IDA-systemet leverer, antagelser og forenklinger, samt tilleggsopplysninger fra andre datakilder. I sammenheng med dette forslaget ble det for hver skredsone bestemt potensielle eksposisjoner og løsnehøyder basert på kartstudier. I tillegg ble skredtype og skredutløser anslått basert på IDA-systemets egenskaper. Det ble også foreslått en modell for å estimere skredets størrelse basert på en sammenligning av skredets lengde og varighet som indikerte at skredets lengde [m] = 20 * skredets varighet [s].
Høyt støynivå på grunn av liten snødybde frem til staren av mars var sannsynligvis en av grunnene til at IDA-systemet på Kattfjordeidet detekterte færre skred enn IDA-systemene i Grasdalen og Indreeidsdalen. Få deteksjoner har gjort det vanskelig å evaluere de definert skredsonene, og bør derfor inngå som videre arbeid. Annet arbeid som bør videreføres er utviklingen av modellen for å estimere skredets størrelse
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