Bachelor-Themen ab FS 2011

Schwermetall Vorkommen im Verrucano (Kt. GL & GR)

Im Abstrom von Vererzungen werden aus Bächen Mineral-Konzentrate entnommen und mittels Röntgenfluoreszenz (XRF) auf ihren Metallgehalt sowie mittels Alpha- und Gammaspektrometrie auf den Gehalt an Uran und Thorium analysiert. Weiter werden in Wasserproben die Nuklide der Uran-Thorium-Serie bestimmt. Ziel: Aussagen zur geogenen Belastung der Umwelt durch Schwermetall-Anreicherungen.

Bedingung: Wasserfest und berggängig

Kontakt: Franz Schenker, Heinz Surbeck

Chromat-Gehalte in Holzaschen

Beim Verbrennen von Holz (Schnitzel, Pellets) zu Heizzwecken werden die im Holz vorhandenen Spuren von Chrom oxidiert und das so entstandene Chromat wird in der Holzasche passiv angereichert. Die Chromat-Gehalte verschiedener Aschen werden nasschemisch analysiert, und die Resultate werden mit den gesetzlichen Anforderungen für die Entsorgung von Abfällen verglichen. Weiter wird die heutige Entsorgungspraxis von Holzaschen beschrieben.

Bedingung: Kommunikationsfreude im Gespräch mit Holzheizern

Kontakt: Franz Schenker

Oszillierende chemische Systeme

regen dank den Erkenntnissen der Chaos-Theorie auch in der Geologie wieder zum Denken an. Als Experiment für die Präsentation in Vorlesungen soll die Belousov Zhabotinsky – Reaktion im Labor durchgeführt und mit Video dokumentiert werden. Weiter sind konkrete geologische Phänomene aufzulisten (inkl. Begründung), bei derer Entstehung möglicherweise dissipative Strukturen beteiligt waren.

Bedingung: Pioniergeist sowie Freude an Laborchemie und Mathematik

Kontakt: Franz Schenker

Seesedimente als Archive natürlicher und anthropgen-induzierte Umweltveränderungen

Das Studium der Seesedimente erlaubt historische und prähistorische Zeitreihen von Oberflächenprozessen im See und im Einzugsgebiet, die häufig mit Naturgefahren in Verbindung stehen (Erdbeben, Bergstürze, Hangrustchungen, Tsunamis). Bachelorprojekte in Limnogeologie untersuchen mittels geophysikalischer, sedimentologischer und geochemischer Methoden den Untergrund der Seen im In- und Ausland. Interpretation dieser Daten rekonstruieren die vergangenen Umwelt- und Klimaveränderungen sowie die Abfolge, Prozesse und Auskwirkungen von Naturgefahren.

Genauere Auskünfte über mögliche Projekte werden bei einem persönlichem Gespräch vermittelt.

Kontakt: Prof. Dr. Flavio anselmetti , Dr. Adrian Gilli

Forensic Statistical Seismology: Searching for recent changes in the homogeneity of the Northern California Earthquake Catalog

The Northern California Earthquake Data Center recently introduced a new approach to compute the magnitudes of earthquakes recorded within the network. A similar change in southern California resulted in drastic changes in the homogeneity of reporting and earthquake scaling laws, with have substantial implications for seismic hazard assessment (Tormann et al., 2010).  In this project, we will search for the telltale signatures of changes in the Northern California dataset, using the techniques already developed for Southern California.

Kontakt: Prof. Stefan Wiemer

Analysis of topographic effects on ground motion (Bachelor or Master)

Theoretical studies based on numerical modelling have shown the strong influence of surface topography on seismic motion. However, such models are usually not able to explain observed seismograms. This is usually explained by unknown subsurface structure, which may together with the topography produce local resonances. Such resonances were identified at one permanent station of Swiss Seismological Service, which is located on a mountain cliff. As a high-quality broadband sensor is installed on the site for more than 10 years, it gives an unique opportunity to monitor temporal changes of the structure. The proposed work will focus on analysis of existing recordings of both earthquakes and ambient vibrations.

Kontakt: Dr. Jan Burjanek, Dr. Donat Fäh

Soil-structure interaction from a building in a sedimentary basin (Bachelor or Master)

Structures like buildings are never perfectly embedded in the soil, resulting among other effects in the modification of the dynamic properties of the structure, and the re-emission of seismic waves from the building to the ground. These effects particularly appear for loose soils in a sedimentary basins. The project includes the study of these effects for a high-rise residential building that is suspected to radiate energy in the Rhone basin in Visp. In-situ tests will be performed in the structure and on the surrounding soil and the radiated energy will be studied at seismic stations of the Swiss Seismological Service. The effects induced by ambient vibrations and by earthquakes will be compared.

Kontakt: Dr. Clotaire Michel, Dr. Donat Fäh

Identification of resonances in complex geological structures (Bachelor or Master)

Array measurements of ambient vibrations can be used to identify two-dimensional resonances in Alpine Valleys. Such resonances are of particular importance during damaging earthquakes, causing a dramatic increase in the amplitudes of strong ground motion. Recently new tools have been developed that have the potential to determine the frequencies of 2D resonances from passive seismic measurement at one station only. The proposed work should explore the usefulness and potential of this new technique, and compare it to results from array method, and finally apply it to different areas in the Valais.

Kontakt: Dr. Jan Burjanek, Dr. Donat Fäh

Characterisation of soft surface layers through active excitation of higher modes Rayleigh waves. (Bachelor or Master)

Shallow surface layers with loose sediments behave very unfavourable during strong earthquakes due to the large amplification of waves and non-linear behaviour such as liquefaction. Such layers are often difficult to identify, especially with passive single-station methods.  Seismic waves trapped in such layers would carry information about the thickness and S-wave velocity in the layer. However the waves are often damped due to strong anelastic behaviour of the soils.  Active excitation of the soft surface layers with a vibrator will therefore be used to excite higher modes Rayleigh waves, and to identify the ellipticity curves of these waves, allowing an estimate of thickness and velocity in the soft layers. The method will be tested and if successful applied to a target region of interest (City of Luzern or Visp).

Kontakt: Dr. Valerio Poggi, Dr. Donat Fäh

Quantification of site amplification at K-Net and Kik-Net stations in Japan (Bachelor or Master)

A new method is applied to define a regional reference rock profile related to a regional ground motion prediction equation for Japan, and to combine average velocity at a site with the frequency-dependent amplification. The large Japanese dataset from the K-Net and Kik-Net is used. The final task is to develop a tool to predict amplification of seismic waves for specific sites that are characterized by the fundamental frequency of resonance of the soils, the polarisation between vertical and horizontal components, and information on the shear-wave velocity profile. The model is compared to a similar model developed for Switzerland using small earthquakes only.

Kontakt: Dr. Ben Edwards, Dr. Valerio Poggi, Dr. Donat Fäh

First break tomography of seismic exploration data from the Okavango Delta Region in Botswana

The group of Applied and Environmental Geophysics at ETH Zurich will conduct a field campaign in the Okavango Delta in Botswana during January and February 2010. The aim of the campaign is to obtain information about the subsurface of the inland delta down to the bedrock in order to reconstruct its complex geological and hydrological history. A series of geophysical methods will be applied. One of them will be the refraction seismic method. The BSc thesis deals with the processing of a  2D seismic data set in order to obtain cross sections of the p-wave velocity distribution in the subsurface down to approximately 300 m, depending on the seismic wave attenuation in that area.  The student will learn and deal with all the conventional processing steps necessary for a first break tomography study. First, the geometry of the seismic survey has to be included in the data. Second, first arrivals of every shot have to be identified and marked. Based on the arrival time of the first breaks and by inversion the p-wave velocity distribution along the survey line will be determined. An inversion code will be used which was developed in the Environmental- and Engineering Geophysics group at ETH Zurich and which is based on an Eikonal forward solver for the computation of travel times in non homogeneous media. The inversion code is ready to use. The BSc thesis will be concluded with an interpretation of the inverted velocity model with respect to the hydrology and geology of the Okavango delta region. A detailed literature study is required for the interpretational part of the thesis.

Kontakt: Dr. Lasse Rabenstein, Dr. Stefan Carpentier, Dr. Heinrich Horstmeyer

Design of direct-current resistivity measurements for a field campaign in the Okavango Delta, Botswana

The group of Applied and Environmental Geophysics at ETH Zurich will conduct a field campaign in the Okavango Delta in Botswana during July and August 2010. One of the geophysical methods that is to be employed during the field campaign is the direct-current resistivity (DCR) method. Here, two pairs of electrodes are employed per measurements: with one pair, a constant current is fed into the subsurface; with the other pair, the resulting potential difference is measured. This potential difference changes according to the distribution of the electrical resistivity in the subsurface. The depth over which the measurements contain information can be increased by increasing the electrode separation. For the Botswana project, the desirable depth range of investigation is tens of metres down to 300m. The aim of the BSc project is to optimally design the layout of the DCR measurements. The procedure is as follows: 1) Synthetic DCR data are generated for pre-assumed models of the electrical resistivity distribution in the subsurface and for several classical DCR electrode layouts. The maximal electrode separations correspond to local conditions in the measurement area. 2) The synthetic data are contaminated with Gaussian white noise of a pre-supposed intensity. 3) The synthetic data are inverted to distributions of electrical resistivity in the subsurface. 4) Simple comparisons with the originally pre-assumed resistivity distribution allow to assess the potential depth range of investigation that can be obtained with a certain set of DCR measurements.

Kontakt: Dr. Thomas Kalscheuer, Dr. Joel Podgorski

Application of Ground Penetrating Radar on glaciers

Ground Penetrating Radar (GPR) is a potentially powerful tool for characterizing glaciers. It allows ice thicknesses and possibly internal structures to be delineated. In the framework of this project extensive measurements with different GPR systems and different antenna types will be performed. It should be determined, which configuration provides the best results for a particular scenario. Data analysis will be performed with Matlab. The conclusions of this thesis project will be highly relevant for future glaciological projects that include GPR measurements.  Data will be collected on alpine glaciers. Skiing skills and preferably a little bit of alpine ski touring experience is required.

Kontakt: Prof. Hansruedi Maurer, Dr. Andreas Bauder