Deciphering Okmok Volcano's restless years (2002-2005)

Thesis (Ph.D.) University of Alaska Fairbanks, 2015Okmok Volcano is an active island-arc shield volcano located in the central Aleutian islands of Alaska. It is defined by a 10-km-diameter caldera that formed in two cataclysmic eruptions, the most recent being ~2050 years ago. Subsequent eruptions created several cinder cones within the caldera. The youngest of these, Cone A, was the active vent from 1815 through its 1997 eruption. On July 12 2008 Okmok erupted from new vents located northwest of Cone D. Between 2001 and 2004, geodetic measurements showed caldera inflation. These studies suggested that new magma might be entering the system. In 2002, a newly installed seismic network recorded quasi-periodic ("banded") seismic tremor signals occurring at the rate of two or more episodes per hour. This tremor was a near-continuous signal from the day the seismic network was installed. Although the volcano was not erupting, it was clearly in a state of unrest. This unrest garnered considerable attention because the volcano had erupted just six years prior. The seismic tremor potentially held insight as to whether the unrest was a remnant of the 1997 eruption, or whether it signaled a possible rejuvenation of activity and the potential for eruption. To determine the root cause and implications of this remarkable seismic tremor sequence, I created a catalog of over ~17,000 tremor events recorded between 2003 and mid-2005. Tremor patterns evolved on the scale of days, but remained the dominant seismic signal. In order to facilitate the analysis of several years of data I created a MATLAB toolbox, known as "The Waveform Suite". This toolbox made it feasible for me to work with several years of digital data and forego my introductory analyses that were based on paper "helicorder" records. I first attempted to locate the tremor using the relative amplitudes of the seismograms to determine where the tremor was being created. Candidate tremor locations were constrained to a few locations along a corridor between Cone A and the caldera center. I then determined theoretical ratios between a reference station and stations nearby the candidate sources. Results suggested that the signal originated in the shallow portion of the corridor connecting the surface of Cone A to the top of the central magma chamber. This study also suggested that the source migrated along this corridor. I integrated the tremor patterns with other studies and proposed that heat and pressure from continued injections of magma were responsible for maintaining an open venting system at Cone A. The tremor resulted from the boiling of a shallow hydrothermal system in the vicinity of Cone A and volatiles potentially coming from the magma itself. The tremor catalog demonstrates that the seismic signal waned during the study period suggesting that fewer fresh volatiles entered the system, which may have allowed the pathways connecting the magma and volatiles to the surface to close up. By the time new magma entered the system in 2006, this network of pathways was closed, forcing the volatiles to seek a new exit. In hindsight, the 2003-2005 period of varied and waning seismic tremor, and the inferred end of massive open venting, may have been a pivotal era at Okmok that eventually led to the 2008 eruption

Rotating and counterrotating relativistic thin disks as sources of stationary electrovacuum spacetimes

A detailed study is presented of the counterrotating model (CRM) for electrovacuum stationary axially symmetric relativistic thin disks of infinite extension without radial stress, in the case when the eigenvalues of the energy-momentum tensor of the disk are real quantities, so that there is not heat flow. We find a general constraint over the counterrotating tangential velocities needed to cast the surface energy-momentum tensor of the disk as the superposition of two counterrotating charged dust fluids. We then show that, in some cases, this constraint can be satisfied if we take the two counterrotating tangential velocities as equal and opposite or by taking the two counterrotating streams as circulating along electro-geodesics. However, we show that, in general, it is not possible to take the two counterrotating fluids as circulating along electro-geodesics nor take the two counterrotating tangential velocities as equal and opposite. A simple family of models of counterrotating charged disks based on the Kerr-Newman solution are considered where we obtain some disks with a CRM well behaved. We also show that the disks constructed from the Kerr-Newman solution can be interpreted, for all the values of parameters, as a matter distribution with currents and purely azimuthal pressure without heat flow. The models are constructed using the well-known "displace, cut and reflect" method extended to solutions of vacuum Einstein-Maxwell equations. We obtain, in all the cases, counterrotating Kerr-Newman disks that are in agreement with all the energy conditions.Comment: 22 pages, 7 figures, Late

Procesamiento espectral para la pseudocuantificación de especies minerales en espectros del instrumento Raman Laser Spectrometer de la misión ExoMars de la ESA

El espectrómetro Raman Laser Spectrometer (RLS) forma parte del conjunto de instrumentos incluidos en el futuro rover que la misión ExoMars de la ESA y Roscosmos enviarán a Marte en 2018. Como instrumento portátil para exploración planetaria, la operación del instrumento deberá ser totalmente autónoma, sin intervención humana. Por tanto, varios paquetes de software y algoritmia deberán ser definidos y optimizados para proporcionar autonomía al instrumento. Por otro lado, debido a la simplicidad y robustez requerida en instrumentos de vuelo, así como la interacción necesaria con otros instrumentos dentro del rover, su modo de operación tiene algunas características que pueden considerarse anómalas para un espectrómetro Raman típico. Por ejemplo, este instrumento analizará un mínimo de 3 20 puntos de una muestra en polvo homogéneamente distribuida, en lugar del habitual análisis en materiales masivos. Por tanto, para obtener del instrumento el máximo retorno científico posible, también es necesario desarrollar técnicas analíticas que se adapten a las características de operación del instrumento. En este trabajo, tanto los aspectos de automatización a bordo como de postprocesado de datos han sido tenidos en cuenta: Se ha propuesto, evaluado y optimizado un algoritmo para la identificación de muestras relevantes a nivel astrobiológico, así como un método estadístico para la pseudo-cuantificación de fases minerales a partir de espectros Raman, y que ha sido probada con muestras reales.Máster en Investigación en Tecnologías de la Información y las Comunicacione

Study of the Gromov hyperbolicity constant on graphs

The concept of Gromov hyperbolicity grasps the essence of negatively curved spaces like the classical hyperbolic space and Riemannian manifolds of negative sectional curvature. It is remarkable that a simple concept leads to such a rich general theory. The study of hyperbolic graphs is an interesting topic since the hyperbolicity of any geodesic metric space is equivalent to the hyperbolicity of a graph related to it. In this Ph. D. Thesis we characterize the hyperbolicity constant of interval graphs and circular-arc graphs. Likewise, we provide relationships between dominant sets and the hyperbolicity constant. Finally, we study the invariance of the hyperbolicity constant when the graphs are transformed by several operators.Programa de Doctorado en Ingeniería Matemática por la Universidad Carlos III de MadridPresidente: Domingo de Guzmán Pestana Galván.- Secretaria: Ana Portilla Ferreira.- Vocal: Eva Tourís Loj

Party Competition over the Centre-Periphery Cleavage. A Comparative Analysis of the Spanish Regions

This investigation is an examination of party competition over the centre-periphery cleavage. The focus is placed on which factors are expected to have a deep effect on the way parties compete when framing the relations between centres and peripheries. The literature has explored different key elements that are able to strongly influence party behaviour along this cleavage, such as for example, party type, ideology, identity, or language. This thesis is centred on other factors that have been overlooked by the same different studies. These are: distance, fragmentation, and polycentricity. The main purpose is to observe the ways in which parties adapt to them in the different regions in which they compete. This research problem is approached via the research question: what factors shape party competition on the centre-periphery cleavage? To answer this research question, the research method used is the sub-national comparative method. This method is applied by using a sequential mix method approach, with a quantitative followed by a qualitative analysis. The purpose of this is obtain at the same time a complete and in-depth understanding of the phenomenon. Employing a case study research strategy, Spain is examined based on the politically salient territorial tensions between its centre and peripheries. In order to observe how the centre-periphery cleavage unfolds, the main sources of information chosen are the political manifestos articulated by parties to compete in regional elections. Addressing the regional level allows to comprehend with more detail how this territorially based cleavage is formulated. From the above three factors, the main findings point in the direction of characterising distance as the element that influence the most the way in which parties compete along the centre-periphery cleavage. The further away a region is from the centre, the more parties territorialise their appeals to the voters. This is followed by fragmentation, which has unexpected and promising results. Polycentricity has to be further analysed in future research agendas, but the results preliminary flag the importance of its different degrees of impact. Finally, these factors are best understood in a qualitative manner in contrast to the literature that also examines Spain, normally based on quantitative data