Fakultät für Geowissenschaften - Digitale Hochschulschriften der LMU

Die Dissertation untersucht die Einsatzmöglichkeiten von Data Mining und Machine Learning in der Entwicklung empirischer Modelle für See-Ökosysteme. Am Beispiel des Ammersees werden hierzu ein Modell zur Berechnung der Wasseroberflächentemperatur aus Lufttemperaturdaten, ein Modell zur Bestimmung der Zirkulationsverhältnisse im Winter sowie ein Modell für den Stoffhaushalt vorgestellt. Anhand dieser Modelle wird unter Verwendung von REMO-UBA-Klimadaten die Entwicklung des Ammersees bis 2050 simuliert.

The aim of this work is to further the understanding of the important parameters in the

formation process of 2D nanostructures and therewith pioneer for novel applications. Such 2D

nanostructures can be composed of specially designed organic molecules, which are adsorbed

on various surfaces. In order to study true 2D structures, monolayers were deposited. Their

properties have been investigated by scanning tunneling microscopy (STM) under ultra-high

vacuum (UHV) conditions as well as under ambient conditions. The latter is a highly

dynamic environment, where several parameters come into play. Complementary surface

analysis techniques such as low-energy electron diffraction (LEED), X-Ray photo-emission

spectroscopy (XPS), and Raman spectroscopy were used when necessary to characterize

these novel molecular networks.

In order to conduct this type of experiments, high technical requirements have to be

fulfilled, in particular for UHV experiments. Thus, the focus is on a drift-stable STM, which

lays the foundation for high resolution STM topographs. Under ambient conditions, the

liquid-solid STM can be easily upgraded by an injection add-on due to the highly flexible

design. This special extension allows for adding extra solvent without impairing the high

resolution of the STM data. Besides the device, also the quality of the tip is of pivotal

importance. In order to meet the high requirements for STM tips, an in vacuo ion-sputtering

and electron-beam annealing device was realized for the post-preparation of scanning probes

within one device. This two-step cleaning process consists of an ion-sputtering step and

subsequent thermal annealing of the probe.

One study using this STM setup concerned the incorporation dynamics of coronene (COR)

guest molecules into pre-existent pores of a rigid 2D supramolecular host networks of trimesic

acid (TMA) as well as the larger analogous benzenetribenzoic acid (BTB) at the liquid-solid

interface. By means of the injection add-on the additional solution containing the guest

molecules was applied to the surface. At the same time the incorporation process was

monitored by the STM. The incorporation dynamics into geometrically perfectly matched

pores of trimesic acid as well as into the substantially larger pores of benzentribenzoic acid

exhibit a clearly different behavior. For the BTB network instantaneous incorporation within

the temporal resolution of the experiment was observed; for the TMA network, however,

intermediate adsorption states of COR could be visualized before the final adsorption state

was reached.

A further issue addressed in this work is the generation of metal-organic frameworks (MOFs)

under ultra-high vacuum conditions. A suitable building block therefore is an aromatic

trithiol, i.e. 1,3,5-tris(4-mercaptophenyl)benzene (TMB). To understand the specific role

of the substrate, the surface-mediated reaction has been studied on Cu(111) as well as on

Ag(111). Room temperature deposition on both substrates results in densely packed trigonal

structures. Yet, heating the Cu(111) with the TMB molecules to moderate temperature

(150 °C) yields two different porous metal coordinated networks, depending on the initial

surface coverage. For Ag(111) the first structural change occurs after annealing the sample

at 300 °C. Here, several disordered structures with partially covalent disulfur bridges were

identified.

Proceeding further in the scope of increasing interaction strength between the building

blocks, covalent organic frameworks (COFs) were studied under ultra-high vacuum conditions

as well as under ambient conditions. For this purpose, a promising strategy is covalent

coupling through radical addition reactions of appropriate monomers, i.e. halogenated

aromatic molecules such as 1,3,5-tris(4-bromophenyl)benzene (TBPB) and 1,3,5-tris(4-

iodophenyl)benzene (TIPB). Besides the correct choice of a catalytic surface, the activation

energy for

Identification of active seismogenic faults in low-strain intraplate regions is a major challenge. The understanding of intraplate earthquakes is hampered by the spatiotemporal scattering of large earthquakes and by barely detectable strain accumulation. In populated humid regions, both hillslope and anthropogenic processes are important challenges to the recognition of potentially active faults.

The Lower Rhine Graben is the NW segment of the European Cenozoic Rift System. It is a prime example of a seismically active low-strain rift situated in a humid and densely populated region. The approximate location of potentially active fault segments in this region is well known, but knowledge of the recurrence of large earthquakes and of the dominant fault slip mode is still rudimentary. The current debate ranges from slip dominated by repeated large earthquakes to slip dominated by aseismic creep.

The purpose of this thesis is to determine whether the Lower Rhine Graben is an exception to the usually observed deformational behaviour of the upper crust, whereby active faults fail by brittle behaviour. The thesis addresses the Holocene, historical and present-day tectonic activity of the Lower Rhine Graben. It examines the signs of coseismic deformation in the geological record, and the surface expression of active fault segments. I analyzed high-resolution LiDAR terrain models of segments of the Erft and Wissersheimer faults, in order to understand the preservation potential of active fault scarps in populated, humid settings. Results of the LiDAR analysis illustrate that the central part of the Lower Rhine Graben is characterized by severe degradation and modification of suspected seismogenic structures. Degradation is due to fluvial erosion, hillslope processes and anthropogenic overprint. This analysis shows, also for the first time, the severity of surface modification of the region resulting from aerial bombing during World War II.

A large trench excavation at the Schafberg fault in Holocene sediments yielded a broadly distributed fault zone with a peculiar abundance of fractured clasts. A particular question at this site is whether or not the fault ruptured in the 1756 AD Düren event. The excavation reveals the first evidence of historical seismogenic faulting in the Lower Rhine Graben. Coseismic deformation at this site is expressed by a net vertical displacement of 1 ± 0.2 m and complex gravel fracturing. Analysis of the faulted strata and radiocarbon ages of event horizons reveal evidence of at least one, possibly two coseismic events since the Holocene. The youngest of them overlaps with the 1756 AD Düren earthquake. The complex deformation pattern in the trench included a range of features such as liquefaction, rotated, and fractured clasts in the fault zone. I developed a new analysis technique based on “fractured-clasts”, which allows insight into coseismic rupture and fracture processes in unconsolidated gravel deposits.

Results of this paleoseismic study show that faults in the Lower Rhine Graben do not move dominantly by aseismic creep. They further support the observation that faults in low-strain intraplate rifts can produce large surface-breaking earthquakes. The results of this thesis further imply that specific patterns of fractured clasts in fault zones may be a detector of coseismic rupture, and could in principle be used to calculate the energy involved in the rupture process.

Die Stadtplanung ist zunehmend mit sozialräumlichen Segregationsprozessen und „gespaltenen Städten“ konfrontiert, die mit gesellschaftlicher Marginalisierung und Ausgrenzung sozial benachteiligter Bevölkerungsgruppen einhergehen. Insbesondere Kinder und Jugendliche mit Migrationshintergrund wachsen zum Teil in problembelasteten Stadtvierteln auf, in denen die einheimische Bevölkerung zur Minderheit geworden ist, was zur Entwicklung von Parallelgesellschaften oder ethnischen Enklaven führen kann. Auch im Bildungssystem lassen sich vielfältige Aspekte von Integration und Segregation beobachten. Besonders gravierend stellt sich die Bildungssituation für die Bewohner sogenannter Problemviertel dar, unter denen Immigranten mit niedrigem sozioökonomischen Status meistens überrepräsentiert sind und deren Kinder sich nur geringe Chancen auf dem Arbeitsmarkt einrechnen können.

In Luxemburg ist man sich der Bedeutung dieses Themas zunehmend bewusst. Die besondere Sprachensituation Luxemburgs sowie die außergewöhnlich hohe Zahl an Migranten führen dazu, dass sich auch in Luxemburg sozialräumliche Segregationsprozesse identifizieren lassen. Im Rahmen der Sozialplanung Luxemburgs wird die soziale Bevölkerungsstruktur genauer analysiert.

Integration fängt bereits in der Schule, wenn nicht sogar in der Vorschule an. Deswegen sind Maßnahmen zur Integration von sozial benachteiligten Kindern in den Schulen und im Umfeld der Schulen besonders wichtig. Mein Promotionskonzept bezieht sich auf die Erweiterung der schulischen und außerschulischen Fördermöglichkeiten, die erforderlich sind, um hauptsächlich in sozial benachteiligten Stadtvierteln der Stadt Luxemburg ein lokales Netzwerk zu schaffen, das erlaubt Bewohner und insbesondere Kinder besser zu integrieren. Ein zentrales Anliegen der Arbeit ist deswegen die Untersuchung der Kooperation zwischen Schulen und der Gemeinde in den jeweiligen Schulbezirken. Dabei stellt die Analyse des sozialen Hintergrunds der Schüler und die Gegebenheiten des jeweiligen Einzugsgebietes der Schule den Ausgangspunkt für diese Untersuchung dar. Eine rein quantitativ ausgerichtete statistische Analyse reicht natürlich nicht aus, um die „Problemschulen“ zu untersuchen. Ergänzend zu den Ergebnissen der Berechnung eines sozialen Indexes für die Schulbezirke werden in ausgewählten Beispielen qualitative Fallstudien durchgeführt, in denen die Wechselwirkungen zwischen schulischen Aktivitäten und kommunalplanerischen Mitteln genauer untersucht werden.

In general, an understanding of the complex processes acting before and during volcanic eruptions is approached from various different sides, e.g. laboratory experiments on fragmentation and/or bubble burst eruption mechanisms, petrological analysis of the eruptive products and various geophysical monitoring and source localization techniques. Each of these techniques can deliver valuable insights by adding pieces of information about the physical processes that drive the volcanic activity. However, often studies are focussing on a single aspect of the process, without setting the results in a more general context. Often, this strategy is absolutely valid, when the focus is laid on a single piece in the complex chain of processes taking place in volcanic eruptions. This must fail when the results

aim to suggest a valid model for the combined observations at volcanoes using the above described techniques. The resulting models of volcanic source mechanisms and eruptive

features can therefore lead to biased assumptions. This study aims to close this gap between laboratory experiments, petro-chemical analysis and modern geophysical monitoring and source localization techniques in a case study of Mt. Yasur (Vanuatu) volcano.

The presented laboratory experiments on explosive volcanic eruptions upon rapid decompression show that decompression rate is the dening parameter in the experiments and that

a scaling to large-scale processes is valid. Furthermore, a model is presented that correlates measured particle velocities to decompression rate and initial gas-overpressure. This model is used to estimate source volumes and overpressures at Volcan de Colima (Mexico) and Mt. Yasur (Vanuatu).

A petrographically and geochemically characterization of Mt. Yasurs eruptive products suggests a shallow magma-mingling process at both of Mt. Yasurs active craters, perhaps due to rejuvenation of material slumped from the crater walls into an open conduit system. A study on the time-reversal imaging technique and its ability to detect the details of finite rupture (or time-variant) processes shows that the limitations of TR imaging start where the source stops being point-localised with respect to the used wavelength.

Inversion of the source mechanisms of Strombolian explosions at Mt. Yasur are performed using a multi-parameter dataset consisting of seismic, acoustic and Doppler-radar data. Time-reversal imaging and moment tensor inversion are used to invert the source location of the seismic long-period (f < 1Hz) signals, which is supposed to refl

ect

fluid movement at depth. The source is located in the north-east of the crater region in a depth of several

hundred meters. Furthermore, the source volume of the radiated infrasound signals is estimated from fundamental resonance frequencies. The results showed that the maximum

particle velocity measured with the Doppler radar correlates nicely with the estimated source volumes lengths. The inverted seismic moment does not show any correlation with the estimated slug sizes, i.e. the slug size does not map in seismic moment. This is an

important information, as it states that a larger source volume does not necessarily produces a larger seismic moment.

From these combined results, a common feeder system for all active craters at Mt. Yasur is proposed. The differences in event recurrence rate at the three active craters are believed to be controlled by either the conduit geometry or variations in degassing or cooling rate.

Strombolian-type eruptions at Mt. Yasur are suggested to be due to the burst of gas slugs with lengths and overpressures comparable to volcanoes showing similar eruptive patterns.

The results illustrate the importance of combined studies that overcome the limitations of single disciplines. In this way, a more comprehensive view of volcanic eruptions and the associated observations is possible. Such a multi-disciplinary approach will contribute to a better understanding of volcanic pro