Fakultät für Geowissenschaften - Digitale Hochschulschriften der LMU

In this thesis I advance the integration of mineral thermodynamics into convection modeling.

I have compiled a thermodynamic model of mantle mineralogy in the five component CFMAS system (CaO-FeO-MgO-Al2O3-SiO2), including mineral phases that occur close to typical chemical models of the mantle and reasonable mantle temperatures. In this system I have performed a system Gibbs free energy minimization, including pure end-member phases and a non-ideal formulation for solid solutions. Solid solutions were subdivided into discrete pseudocompounds and treated as stoichiometric phases during computation of chemical equilibrium by the simplex method. I have complemented the thermodynamic model with a model of shear wave properties [Stixrude and Lithgow-Bertelloni, 2005] to obtain a full description of aggregate elastic properties (density, bulk and shear moduli) that provide a useful basis for the consideration of seismic and geodynamic models of the Earth's mantle.

By using this new thermodynamic database for the mantle I have coupled the resulting density dynamically

(through the buoyancy term) with mantle convection models.

I have linked the

database with a high-resolution 2-D convection code (2DTERRA), dynamically coupling the thermodynamic model (density) with the conservation equations of mantle flow.

The coupled model is run for different parameterisations of viscosity, initial

temperature conditions, and varying internal vs. external heating.

A common feature of all the models is that the convecting flow creates a characteristic discontinuity of temperature around 660 km depth in order to compensate for the entropy change due to the phase transitions.

I have studied the importance and the possible consequences of such a thermal regime on the excess temperature of plumes and on the transition zone thickness.

The thermodynamic mantle mineralogy model provides the conversion of the temperature field into

seismic velocities so that predictions from mantle convection can be compared to seismic observations in terms of radial profiles or lateral variations.

This approach allows us to predict a number of seismic

observables from the convection model, all of which agree remarkably

well with observations from seismic tomography.

Deterministic earthquake scenario simulations are playing an increasingly important role in seismic hazard and risk estimation. The numerical calculation of the complete 3D wavefield in the observed frequency band for a seismically active basin remains a computationally expensive task. This expense restricts seismologists either to calculating source models with homogeneous media (e.g., Gallovic and Brokesoová, 2004, 2007a,b), or to calculating single source scenario in 3D media (e.g., Olsen and Archuleta, 1996; Olsen, 2000; Ewald et al., 2006) while the complex effects of the media and the source on the ground motion are getting more and more attention. At the same time, with the development of the instrument, ground rotation introduced by an earthquake becomes a more and more important topic. Our aim is to provide a tool with which we can calculate a large number of different finite-source scenarios for a particular fault or fault system located in a 3D structure which will enable us to estimate ground motion (translation and rotation) variations due to source and 3D structure. In order to avoid having to run numerical expensive 3D code for each kinematic source scenario we propose the concept of “numerical Green’s functions” (NGF): a large seismic fault is divided into sub-faults of appropriate size for which synthetic Green’s functions at the surface of the seismically active area are calculated and stored. Consequently, ground motions from arbitrary kinematic sources can be simulated for the whole fault or parts of it by superposition.

To demonstrate the functionalities of the method a strike-slip NGF data base was calculated for a simplified vertical model of the Newport-Inglewood fault in the Los Angeles basin. As a first example, we use the data base to estimate variations of surface ground motion (e.g., peak ground velocity (PGV)) due to hypocentre location for a given final slip distribution. The results show a complex behavior, with dependence of absolute PGV and its variation on asperity location, directivity effect and local under-surface structure. Hypocentral depth may affect peak ground velocity in a positive or negative way depending on the distance from the fault and the receiver location with respect to basin structure.

Finite-fault source inversions reveal the spatial complexity of earthquake slip over the fault plane. In this study, several possible earthquake scenarios of Mw 7.0 are simulated with different quasi-dynamic finite source models for the Newport-Inglewood fault in the Los Angeles basin. We investigate the effects of the various slip histories on peak ground velocities and the related variations in ground motion prediction for our study area. The results confirm that the fault perpendicular components of motion are dominated by directivity effects while the fault parallel component is influenced both by the slip distribution and the basin structure. There are theoretical considerations suggesting that observations/calculations of the rotation part of earthquake-induced ground motions may provide additional information for earthquake risk hazard analysis after reports on rotational effects on structures (like twisting of tombstones or statues). For the first time, we carry out a systematic study of earthquake scenario simulations in 3D media with a specific focus on the rotational part of the motions. We simulate several M7 earthquakes with various hypocentre locations and slip histories on the Newport-Inglewood fault embedded in the 3D Los Angeles Basin. We investigate source

and basin structure effects on the rotational components of ground motion (e.g., peak ground rotation rates and their variation, horizontal gradients) and compare with the effects on translations.

Igel et al. (2005) shows a similarity of the observed waveforms between transverse acceleration and the vertical rotation rate in the teleseismic range benefiting from the recently developed ring laser instruments. The vertica

Den Fragen der Erarbeitung des Naturgefahrenmanagements in Gebirgsystemen SO-Kasachstans und in den Ländern des Zentralasiens insgesamt wurde bisher keine gebührende Aufmerksamkeit zuteil. Die Naturkatastrophen der letzten Jahrzehnte sowie die Erfahrung mit Maßnahmen zum Schutz des Ile-Alatau vor Naturgefahren haben gezeigt, dass die Lösung dieser Probleme für die weitere nachhaltige Entwicklung dieser Region von erstrangiger Bedeutung ist.

In dieser Arbeit wurde vom Autor umfangreiches Material zur komplexen Untersuchung der Gebiete des Ile-Alatau zusammengetragen und analysiert (u. a. durch eigene Forschungen, die im Rahmen der Forschungsprojekte des Institutes für Geografie des Ministeriums für Bildung und Wissenschaft der Republik Kasachstan durchgeführt wurden).

Die Hauptmethoden der Arbeit waren Auswertung vorhandener Daten- und Kartenmaterialien, Auswertung von Fernerkundungsdaten, eigene Geländearbeiten und Kartierungen zu Naturrisiken, Recherchen bei Behörden, Befragungen.

In der Dissertation wurden zunächst die Naturbedingungen (u. a. Orographie, Relief, Geologie, Klima und Vegetation) sowie der Stand der Naturrisikoforschung im Ile-Alatau dargestellt. Eine Klassifikation der wichtigsten Naturgefahren im Ile-Alatau wurde vorgenommen und die historischen Naturkatastrophen beschrieben. Die Statistiken und Materialien über den durch Lawinen, Muren und Erdrutsche entstandenen Schaden wurden untersucht. Die regionale und zeitliche Verteilung, die Charakteristik, Ursachen und Auswirkungen der ausgewählten Naturgefahren (Lawinen, Muren, Hangrutschungen, Bergstürze/Steinschläge) wurden analysiert. Es wurden Daten über die Verteilung gefährdeter Zonen in den Einzugsgebieten des Ile Alatau angeführt.

Die Analyse dieser Daten hat gezeigt, wo die Lawinengefahr im Ile-Alatau territorial am stärksten verbreitet ist. Im zentralen Teil sind über 50 % der Fläche davon betroffen. Die maximale Murengefahr wird auch im zentralen Teil des Ile-Alatau verzeichnet. Die größten Bergstürze und Hangrutschungen wurden von Erdbeben verursacht. Alle diese untersuchten Naturprozesse mit verschiedenen Auswirkungen finden im untersuchten Gebiet jährlich statt.

Auf dieser Basis der Analyse wurde dann das Risiko bewertet, das von den ausgewählten Naturgefahren ausgeht. Grundlage dafür war die Analyse der Häufigkeit, der Verbreitung und des Ausmaßes der Prozesse. Eine Einteilung des Gebiets nach Gefährdung durch natürliche Prozesse und nach deren Risiko wurde vorgenommen. Dazu wurden Karten der Naturgefahren und deren Risiko erstellt. Nach Datenschutzgesetz der Republik Kasachstan darf der Autor keine Karten in Großmaßstab veröffentlichen. Diese sind nur zur internen Benutzung in Kasachstan zugelassen.

Die zur Zeit getroffenen Schutzmaßnahmen im Ili-Alatau wurden unter Bewertung ihrer Wirksamkeit untersucht. Die ökonomische Effektivität der Durchführung der Lawinenschutzmaßnahmen wurde für das Einzugsgebiet des Flusses Kischi Almaty berechnet.

Ein unter den Bedingungen des Ile-Alatau am besten geeignetes Schema des Naturgefahren- und Risikomanagements bei Umsetzung von Präventivmaßnahmen, bei Sicherungs- und Rettungsmaßnahmen und bei Wiederherstellungsmaßnahmen wurde vorgeschlagen. Die Arbeit enthält ebenfalls Empfehlungen zur Verbesserung der Funktion der Dienste des Naturgefahrenmanagements.

Konkrete Empfehlungen zum Schutz des Territoriums und der Bevölkerung vor Naturgefahren und zur Verminderung des Schadens wurden gegeben. Gebiete, die von den natürlichen Prozessen am stärksten gefährdet sind, wurden erfasst und die notwendigen optimalen Maßnahmen für ihren Schutz empfohlen.

Die Erfahrung der im Ile-Alatau durchgeführten Arbeiten ermöglicht es, Naturgefahren zu analysieren und zu bewerten, um ein Naturgefahrenmanagement zu erarbeiten, das eine nachhaltige Entwicklung auch in anderen Gebirgssystemen Kasachstans und in anderen Ländern Zentralasiens gewährleistet.

By storing and transporting vast amounts of energy derived from solar insolation, the oceans play an important role in shaping Earth’s climate. On the largest scale, ocean currents smooth the temperature gradients between the equator and the poles by redistributing excess energy from the tropics to higher latitudes. Much of this excess heat is transported by the so-called Ocean Conveyor Belt (Broecker, 1991), a global network of ocean currents driven by thermohaline convection. Changes in the pattern and strength of thermohaline circulation affect the redistribution of heat, and thereby significantly influence climate on local to global scales.

The reconstruction of paleocurrents has long been a subject of paleoceanographic research. Among the various methods employed in tracing paleocurrents (and modern currents), the Sm-Nd isotope system is experiencing ever increasing attention. First applied in an oceanographic context by O’Nions et al. (1978), it is by now established as a standard tool, as shown by numerous recent publications (e.g. Rutberg et al., 2000; Tütken et al., 2002; Weldeab et al., 2002; Benson et al., 2003; Farmer and Barber, 2003; Piotrowski et al., 2004; Bayon et al., 2002, 2003, 2004; Lacan and Jeandel, 2001, 2004, 2005, and many more). Two lines of application of the Sm-Nd isotope system to oceanography/paleoceanography can be distinguished, both of which were followed for this thesis.

The first approach uses the isotopic composition of Sm and Nd hosted in detrital minerals to infer the provenance of terrigenous sediments. This information can be used to draw conclusions about the direction and distance of sediment delivery. The second approach uses the isotopic signature of Nd as a tracer of different water masses. Due to the oceanic residence time of Nd being shorter than the global turnover rate of seawater (500-1000 years vs ~1000 years; Tachikawa et al., 2003), different bodies of water acquire distinct Nd isotopic signatures as a function of the age of adjacent continents. Apart from directly analyzing the Nd isotopic compositions of water samples to trace the modern distribution of different watermasses (e.g. Lacan and Jeandel, 2001, 2004), suitable archives of seawater-derived Nd can be employed to study paleocurrents. Possible archives are fossil remains of marine organisms (e.g. foraminifers; Burton and Vance, 2000), or, most widely used for the recent geological past, Fe-Mn nodules and crusts (e.g. Frank et al., 2002). With slow growth rates on the order of mm/Ma, however, Fe-Mn nodules do not offer the high temporal resolution necessary to study Late Quaternary climate change. Attention has therefore recently turned to authigenic Fe-Mn oxyhydroxides finely dispersed throughout the sediment column (e.g. Rutberg et al., 2000; Bayon et al., 2002, 2003, 2004; Piotrowski et al., 2004).

For this thesis, both lines of application of the Sm-Nd isotope system to paleoceanography were followed. The samples were taken from a sediment core collected from the Yermak Plateau in the north-eastern Fram Strait. Situated between Greenland and the Svalbard Archipelago, the Fram Strait is the only deep connection between the Arctic Ocean and, via the Greenland-Iceland-Norwegian (Nordic) Seas, the North Atlantic. The Nordic Seas are an area of deep-water formation important for the global thermohaline circulation. There, the processes of deep-water formation are in a state of equilibrium that is most sensitive to changes in surface water salinity, which, in turn, is strongly influenced by the outflow of water of low salinity from the Arctic Ocean. This makes the history of water exchange between the Atlantic and the Arctic Ocean through the Fram Strait a subject of key interest for climate research.

In particular, it was attempted to reconstruct the provenance of sediments deposited on the western Yermak Plateau over the last 129 000 years. This was done by analyzing samples from the sediment core and from poten

A method is developed to incorporate prior fuzzy knowledge about reflectance behavior of land cover types into the segmentation of reflectances from moderate scale remote sensing data. The procedure is applied to aggregated Landsat TM data and to MODIS data and used to derive land cover type specific leaf area index.

Community participation and decentralization within the public health sector are the key elements of the Health Care Reform 2002 in India. Focus of research is the implementation of health policy in rural areas of Himachal Pradesh, West Bengal and Maharashtra. Status of participation in the selected districts, status of decentralization in the public health system and prerequisites for successful participation are examined to predict outcomes of the Health Care Reform on quality of health care.