MSc Students 2012-2013

Jamyang Chophel

Landslide Detection and characterization in Bhutan from seismological and remote sensing data

Rock slope failures, soil slides and debris flows (very rapid and extremely rapid landslides) constitute a significant natural hazard in Bhutan. Earth and debris slides and flows commonly occur after the high precipitations of the Summer Monsoon, between May and September each year. All types of landslides are also known to be triggered by local and regional earthquakes. Landslides are a major hazard not only because of their direct destruction but also as they usually block the few existing roads; by that they cut access for days’ to weeks’ time, and also delay rescue teams in case of an earthquake. Landslides may also block rivers creating temporary lakes with the added hazard of outburst flood.

Landslides in most countries are usually reported by the population upon direct observation. However no information is available in areas of the world that are more scarcely inhabited. In this master thesis a combined approach is proposed to (1) detect landslides using seismic noise, (2) compare the results with remote sensing and local data (ground truthing), and (3) provide and discuss the characteristics of the observed landslides.

Andres Gustav Calüna

Complex Rock-Debris Slides - Impact Triggering of Debris Avalanches (Stampa, Norway)

As a part of a nationwide landslide mapping project financed by the Norwegian Water and Energy Directorate (NVE), the geological survey of Norway (NGU) has detected and characterized several large rock slope instabilities in three counties (Møre og Romsdal, Sogn og Fjordane, and Troms) with a history of large destructive rock avalanches in the past. Many of these sites are currently under periodical monitoring. Several instabilities are located in the vicinity of human settlements, and their possible catastrophic failure would potentially produce large destruction. One of the most critical areas in the Sogn og Fjordane county is located above the village of Flåm, where one of the largest active rockslide areas of Norway has been identified. Large rockslide deposits have been mapped inside the fjord and in the lower part of the slopes below the currently unstable rock masses. Inside of the larger area, two sites (Joasete & Høgsete) have been identified as the most active. The municipality, the county and institutions on the governmental level are concerned about the stability conditions, and especially the possibility of a major slope collapse with large consequences. The objectives of this MSc Thesis are twofold, first to evaluate the possibility that an impact from a rockslope failure on Joasete could trigger failure of the talus deposits using deterministic and/or numerical methods; secondly to assess the runout behavior of triggered rockslide-debris avalanche into the fjord using numerical models.

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Antoine De Preux

Permafrost Rockslope Failure (Piz Cengalo)

Maité Sarah Eisner

Detecting long-term bedrock displacement and slow moving landslides with InSAR in the paraglacial environment of the Aletsch glacier

This project will use satellite-borne InSAR (radar interferometry) to analyze long-term bedrock displacements in the Aletsch glacier region. The primary goal is to measure long-term uplift and/or subsidence associated with glacial retreat and changing hydrogeology. A further goal is to measure seasonal deformation signals induced by coupled thermo- and hydro-mechanical effects. A supplementary outcome will be the detection of ongoing slope movements related to rock slope instabilities and/or periglacial phenomena. Together these outcomes will contribute to a better understanding of how rock slopes in an actively deglaciating environment respond to imposed changes in boundary conditions. The study area for our project is the Aletsch glacier region, from the Jungfrau to the glacier tongue (15 x 20km). This project will be conducted through collaboration between the Engineering Geology Group and the Institute of Environmental Engineering at ETH Zurich.

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Agnete Hoff Finnöj (ERASMUS)

Hrafnhildur_Héðinsdóttir

Thermal Fracking in Geothermal Wells (Iceland)

This project will examine thermal stimulation data from high-temperature geothermal fields including those in Iceland to evaluate whether shearing of natural fractures through which the injected fluid enters the reservoir might account for the observed permeability increases. The study will conclude with a simple modeling-based parameter study to assess the conditions under which thermal stress changes on the inlet fractures might promote shearing under stimulation injection conditions.

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Marc Hugentobler

Ambient Vibrations and Unstable Slopes - Detailed Study

Marcin Bogumil Janik

Ambient Vibrations of Unstable Rock Slopes - General Study

Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. This MSc thesis is part of an interdisciplinary project between Engineering Geology and Seismology (Swiss Seismological Service SED), in which we analyze ambient vibration and earthquake recordings to obtain the seismic response of unstable rock slopes. Recorded ground motion is highly directional in the unstable part of the rock slope, and significantly amplified with respect to stable areas. Such a unique signature might improve our understanding of slope structure and stability. We therefore perform systematic measurements and interpretation of ambient vibrations at known unstable rock slopes, both with double stations and arrays. Retrieved seismic parameters will be compared with independent engineering geological in-situ observations and available data. The interpretation of recordings targets the estimation of the potential landslide volume. The expected output is a classification scheme to characterize slope structure and possibly infer potential slope instability from the ambient noise recordings.

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Susanne Myhre (ERASMUS)

Marco Pally

Factors controlling slow or extremely rapid failure of large rock slope instabilities (Flam Region, Western Norway)

The area around the village of Flåm in the Sogn og Fjordane county (Norway) presents a complex history with a large number of rock slope instabilities and past failures of different types and magnitudes. Instabilities can be found on both sides of the Aurlandfjord and the Flåm valley. Several of these instabilities have been studied at different levels of detail by the Geological Survey of Norway (NGU) during the last decade as a part of a nationwide landslide mapping project financed by the Norwegian Water and Energy Directorate (NVE). NGU’s work is focused in the investigation of large instabilities with a high potential of a catastrophic collapse that can affect populated areas. However, not all large rock slope instabilities fail catastrophically, i.e. in large and extremely rapid events leading to long runout rock avalanches. Some large rock slope instabilities show signs of long term creep without failure, leading to multiple small scale rockslides with significantly less runout distance, damage and risk to population. The distinction between these two types of failure modes is of highest practical importance, but little research has been carried out in the past to reliably predict these two contrasting behavior types. The area of Flåm is considered suitable for the analysis of large rock slope instabilities, which might or might not develop into catastrophic failures. The objective of this MSc Thesis is to investigate the factors controlling long term creep or catastrophic failure of large rock slope instabilities in the Flam region. The student will systematically compare release areas, slope failure deposits, slope kinematics, rock mass structure, rupture/sliding plane materials and geometry of all past and ongoing slope instabilities.

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Martin Pettersen (ERASMUS)

Mischa Fabian Schweingruber

Active Thermal Tracer Testing at the Widen Site, Thur Valley

By an active thermal tracer test (TTT), hot or cold water is injected into the aquifer instead of conventional dye tracers. Within this project, a TTT will be planned, conducted and interpreted. Field experiments are foreseen at the well-equipped and well investigated Widen test site of the RECORD project (collaboration with Eawag). The site is located in the Thur valley, where over 20 observation wells are installed. The task is to inject an “appropriate volume” of hot and/or cold water as well as a dye tracer together, and monitor depth- and time-dependent evolution of the responses at the observation wells. For the interpretation of the results, both energy balance calculations and simple analytical simulation will be considered. If possible, a numerical models is set up and calibrated to the field data. Main questions will be the identifiability of flow and transport parameters, the role of aquifer heterogeneity, and macrodispersion.

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Magni Vestad (ERASMUS)

Sebastian Zimmer

Stress heterogeneities characterisation from borehole failure analyses at Superior, Arizona

Stress heterogeneity is thought to play an important role in many aspects of crustal mechanics, including the influencing of the space-time distribution and scaling of earthquakes. Unfortunately, too little is known about the magnitudes of spatial variations of stress in the crust, primarily because stress heterogeneity is so difficult to measure. Borehole breakouts and drilling induced tensile failure gives a unique insight in stress heterogeneity, because on the contrary to typical measurement techniques that are essentially point measurements, they provide continuous profiles of stress orientation and relative magnitudes. In this thesis, an exceptional data set including more than 60 boreholes fully imaged with acoustic borehole televiewer and presenting extensive borehole failure will be used to investigate the spatial characteristics of stress heterogeneity.

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