abstract: Silicic volcanoes produce many styles of activity over a range of timescales. Eruptions vary from slow effusion of viscous lava over many years to violent explosions lasting several hours. Hazards from these eruptions can be far-reaching and persistent, and are compounded by the dense populations often surrounding active volcanoes. I apply and develop satellite and ground-based remote sensing techniques to document eruptions at Merapi and Sinabung Volcanoes in Indonesia. I use numerical models of volcanic activity in combination with my observational data to describe the processes driving different eruption styles, including lava dome growth and collapse, lava flow emplacement, and transitions between effusive and explosive activity. Both effusive and explosive eruptions have occurred recently at Merapi volcano. I use satellite thermal images to identify variations during the 2006 effusive eruption and a numerical model of magma ascent to explain the mechanisms that controlled those variations. I show that a nearby tectonic earthquake may have triggered the peak phase of the eruption by increasing the overpressure and bubble content of the magma and that the frequency of pyroclastic flows is correlated with eruption rate. In 2010, Merapi erupted explosively but also shifted between rapid dome-building and explosive phases. I explain these variations by the heterogeneous addition of CO2 to the melt from bedrock under conditions favorable to transitions between effusive and explosive styles. At Sinabung, I use photogrammetry and satellite images to describe the emplacement of a viscous lava flow. I calculate the flow volume (0.1 km3) and average effusion rate (4.4 m3 s-1) and identify active regions of collapse and advance. Advance rate was controlled by the effusion rate and the flow’s yield strength. Pyroclastic flow activity was initially correlated to the decreasing flow advance rate, but was later affected by the underlying topography as the flow inflated and collapsed near the vent, leading to renewed pyroclastic flow activity. This work describes previously poorly understood mechanisms of silicic lava emplacement, including multiple causes of pyroclastic flows, and improves the understanding, monitoring capability, and hazard assessment of silicic volcanic eruptions. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2016

Dans cette thèse, nous étudions le problème de la localisation de sources sismo-volcanique, à partir des données enregistrées par des réseaux de capteurs composés de nouveaux sismomètres à trois composantes (3C). Nous nous concentrerons sur le volcan Ubinas, l'un des plus actifs au Pérou. Nous développons une nouvelle approche (MUSIC-3C) basée sur la méthode MUSIC permetant de retourner les 3 paramètres utiles (lenteur, azimut et incidence). Pour valider notre méthodologie, nous analysons des sources synthétiques propagées en tenant compte de la topographie du volcan Ubinas. Dans cette expérience, les données synthétiques ont été générées pour plusieurs sources situées à différentes profondeurs sous le cratère Ubinas. Nous utilisons l'algorithme MUSIC-3C pour les relocaliser. Nous traitons également des données réelles provenant d'une expérience de terrain menée sur le volcan Ubinas (Pérou) en 2009 par les équipes de recherche de l'IRD-France (Institut de Recherche pour le Déveleppment), UCD l'Irlande (projet VOLUME) et l'Institut de Géophysique du Pérou (IGP). Nous utilisons l'algorithme MUSIC-3C pour localiser les événements explosifs (type vulcanien), ce qui nous permet d'identifier et d'analyser les processus physiques de ces événements, à la suite de cette analyse, nous avons trouvé deux sources pour chaque explosion situées à 300 m et 1100 m en dessous du fond du cratère actif. Basé sur les mécanismes éruptifs proposés pour d'autres volcans du même type, nous interprétons la position de ces sources ainsi que les limites du conduit éruptif impliqué dans le processus de fragmentation. / In this thesis, we study the seismo-volcanic source localization using data recorded by new sensor arrays composed of three-component (3C) seismometers deployed on Ubinas stratovolcano (Peru). We develop a new framework (MUSIC-3C) of source localization method based on the well-known MUSIC algorithm. To investigate the performance of the MUSIC-3C method, we use synthetic datasets designed from eight broadband isotropic seismic sources located beneath the crater floor at different depths. The fundamental scheme of the MUSIC-3C method exploits the fact of the cross-spectral matrix of 3C array data, corresponding to the first seismic signal arrivals, provides of useful vector components (slowness, back-azimuth and incidence angle) from the seismic source. Application of the MUSIC-3C method on synthetic datasets shows the recovery of source positions. Real data used in this study was collected during seismic measurements with two seismic antennas deployed at Ubinas volcano in 2009, whose experiment conduced by volcanic teams of IRD-France (l'Institute de Recherche pour le Déveleppment), Geophysics group University College Dublin Ireland and Geophysical Institute of Peru (IGP). We apply the MUSIC-3C algorithm to investigate wave fields associated with the magmatic activity of Ubinas volcano. These analysis evidence a complex mechanism of vulcanian eruptions in which their seismic sources are found at two separated sources located at depths of 300 m and 1100 m beneath the crater floor. This implies the reproduction of similar mechanisms into the conduit. Based on the eruptive mechanisms proposed for other volcanoes of the same type, we interpret the position of this sources as the limits of the conduit portion that was involved in the fragmentation process.

Durant mes trois années de thèse, j'ai été amenée à travailler sur différents aspects de la surveillance des propriétés élastiques de la croûte, à la fois par analyses numériques, mais aussi par des applications d'utilisation du bruit ambiant. Ma thèse s'articule autour de deux parties principales: Les propriétés des ondes de la coda Le libre parcours moyen est un paramètre crucial rencontré continuellement dans les différentes parties de mon travail. Dans cette partie, je présente une nouvelle façon de déterminer ce libre parcours moyen à partir des statistiques de phase. Cette méthode a été testée avec succès dans l'étude d'un volcan situé en Auvergne (France). Je présente ensuite une analyse numérique de la sensibilité que les ondes de la coda manifestent en fonction de la profondeur. Ce travail nous a permis de relier cette sensibilité à la profondeur observée dans les ondes de la coda, à une combinaison de la sensibilité des ondes de volume et de celle des ondes de surface. En effet, cette sensibilité des ondes de volume et de surface dépend directement du temps considéré dans la coda et du libre parcours moyen du milieu étudié. Nous avons été capable de montrer que le changement de vitesse relatif dans la coda était lié à une dépendance en temps. Cette importante observation nous permet de pouvoir établir une distinction entre un changement qui se produit en surface et un changement ayant lieu en profondeur. Localisation des changements dans un milieu diffusif Nous avons développé une méthode d'inversion basée sur des approches probabilistes de la propagation des ondes, afin de pouvoir localiser les changements dans le milieu. Nous avons également étudié la décohérence de la forme d'onde, ce qui constitue un aspect additionnel des techniques de surveillance du bruit sismique, qui traditionnellement sont basés sur l'évaluation du temps de retard dans la coda. Au cours de cette thèse, nous avons affiné notre méthode d'inversion en l'appliquant à trois cas d'études. Dans un premier cas, nous avons étudié les changements ayant eu lieu avant et pendant l'éruption du volcan du Piton de la Fournaise situé sur l'Ile de la Réunion. Le challenge ici est de parvenir à localiser correctement la prochaine éruption. La seconde application a concerné le séisme de Mw7,9 de Wenchuan (Chine), sur lequel nous avons obtenu de nombreuses données. Dans ce cas, nous avons pris en compte l'évolution de la coda au cours du temps et nous avons conjointement inversé les données à différents temps dans la coda pour étudier les changements induits dans la croûte, avant et pendant le séisme. A partir de ces résultats, nous avons pu clairement voir que la décohérence de la forme d'onde et les variations de vitesse n'étaient pas sensibles aux mêmes propriétés physiques. Dans le troisième cas d'étude, nous avons testé la procédure d'inversion avec un noyau 3D pour étudier la fracturation dans un bloc de béton soumis à une contrainte croissante. / During my thesis, I worked on different aspects of monitoring the elastic properties of the crust, with both numerical analysis and applications with ambient noise. The main body of my thesis consists of two main parts: 1. Properties of coda waves A very important parameter that we continuously encounter in the different parts of my thesis work is the scattering mean free path. I present an original way to determine the scattering mean free path from phase statistics that was successfully tested on a volcano in Auvergne. Then I discuss an intensive numerical analysis of the depth sensitivity of coda waves. This work allowed us to relate the depth sensitivity of coda waves to a combination of bulk wave sensitivity and surface wave sensitivity that depends on the time in the coda and on the scattering mean free path of the medium. We were able to show a time dependence of the relative velocity change in the coda that allows us to discriminate a change that occurs at the surface from a change that occurs at depth. 2. Locating changes in multiply scattering media We developed an inversion method based on probabilistic approaches of the wave propagation to locate changes in the medium. As an additional aspect to seismic noise monitoring techniques that are based on the evaluation of time delays in the coda, we also study the waveform decoherence. Within this thesis, we apply and refine the inversion method with three case studies. We study pre-and co-eruptive changes at Piton de la Fournaise volcano in La Réunion Island. The challenge here is to correctly locate forthcoming eruptions. A second data set comes from the Mw7.9 Wenchuan earthquake in China. In this study, we take the time evolution of the coda into account and jointly invert the data at different times in the coda to study changes in the crust during and after the earthquake. From the results, we can clearly see that waveform decoherence and velocity variations are not sensitive to the same physical properties. In the third study, we test the inversion procedure with a 3D sensitivity kernel to study the fracturing of concrete blocks under increased tension.

Le 26 octobre 2010, le Merapi, volcan le plus peuplé et le plus actif de l'île de Java en Indonésie, est entré en éruption. Depuis plusieurs mois, l'activité du volcan avait crû de manière exponentielle et les scientifiques s'attendaient à une éruption exceptionnelle. Leurs pronostics furent confirmés puisqu'un blast parcourut une distance de 8 km, rasa en partie deux villages évacués, et tua mbah Marijan, le « gardien des clés du volcan » et son entourage, ce qui perturba l'équilibre culturel de la région. Dans les jours suivants, l'activité du volcan continua de s'intensifier et des évacuations massives furent organisées. L'éruption paroxysmale du Merapi eut lieu dans la nuit du 4 au 5 novembre ; alors que plusieurs dizaines de milliers de villageois étaient en train de fuir le volcan, de puissantes coulées pyroclastiques dévastèrent les flancs du volcan, tuant et détruisant tout sur leur passage sur une distance maximale de 17 km. Cette nuit-là, plus de 250 personnes furent tuées et des milliers d'autres blessées. Le secteur agricole subit de lourdes pertes puisque de nombreuses récoltes et un grand nombre de têtes de bétail furent perdus. L'activité touristique de la région connut une réaction en chaîne d'impacts, générée en grande partie par la fermeture de l'aéroport de Yogyakarta. La thèse propose de faire une étude transversale et systémique de ces impacts en analysant comment gouvernement et populations se remettent de cette éruption et s'apprêtent à faire face à une future crise causée par le Merapi. / On October 26th 2010, the Merapi volcano, the most populated and active volcano on the Java Island in Indonesia, began erupting. During several months, the volcano's activity grew exponentially and scientists were expecting an exceptional eruption. Their predictions got confirmed as a blast ran through a distance of 8 km, partially destructed two villages (that got evacuated) and killed mbah Marijan, the « Volcano's keys guardian » and his entourage. As a consequence, the cultural balance of the region got disrupted for a while. In the following days, the volcano's activity kept increasing and mass evacuations were organized. The paroxysmal eruption of Merapi occurred in the night of November 4th to 5th 2010, while tens of thousands of villagers were running away from the volcano. Powerful pyroclastic flows ran down its flanks, killing and destroying everything on their way over a maximum distance of 17 km. During that night, over 250 people were killed and thousands were injured. The agricultural sector suffered from heavy losses as many crops and livestock were lost. The tourism industry in the region experienced a chain reaction of impacts generated by the closure of Yogyakarta airport. The thesis offers to make a transversal and systemic study of these impacts by analyzing how the government and people recovered from the eruption and how they are to face a future crisis caused by the Merapi.

As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motionthe elastic response to winter accumulation and spring melt seasonswith peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1 sigma confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.

This thesis acknowledges the presence of a clear note of affirmation in some novels of the mid-Twentieth Century. Finding a similar affirmation in Albert Camus' essays, The Myth of Sisyphus and The Rebel, it attempts to demonstrate a basic agreement between the essays and a limited selection of such novels. It then attempts to support this conclusion by examination of two novels in some detail. It considers that this relationship arises naturally from the artists' mutual perception of man's perilous condition in the modern world, and that it does not imply the necessity of conscious imitation of Camus' thoughts on the absurd. Nevertheless, since this thesis intends to show that the affirmation in the novels arises from an attitude that Camus termed "absurdist" and inheres in a way of life that he termed "absurd," such novels, for the purpose of this study, are called "Absurd." Chapter One attempts to explain man's existential anxiety as a spiritual state germane to his condition as an intelligent being in an obscure universe, and to describe how this natural anxiety, painfully intensified in a godless, materialistic age, has resulted in spiritual sterility and paralysis of creative action. Of this condition, such novelists as Malcolm Lowry, Joseph Heller, William Golding, Lawrence Durrell and William Styron seem acutely aware. In addition, it attempts to define Camus' uses of the term "absurd," and to explain the nature of the absurd life—the life of absurd rebellion—that he advances as the only-positive answer to the challenge of the times. While recognizing that the diversity evident among these novels attests to their nature as independent creations, Chapter One attempts to establish their basic agreement with Camus' ideas of the absurd, and to trace the existence among them of broad similarities. Finally, by examination of values implied, it notes that these authors seem to arrive at Camus' conclusion that "everything is permitted," limited, as Camus limits it, by the necessity of individual responsibility. Chapters two and three, detailed examinations of the absurd in two novels, Malcolm Lowry's Under the Volcano and Joseph Heller's Catch-22, attempt to clarify the nature of the authors' protest by pointing out what forces, both external and internal, are attacked. As this process involves an analysis of the nature and results of destructive escapism, whether individual escape into alcoholism or mass escape into meaningless conformity or excessive rationalism, it suggests also the urgency of the individual struggle for the "lucid awareness" that Camus demands. In particular, these chapters hope to clarify the affirmation implied by the individual liberation from illusion and anxiety to defiant joy in conscious living. The Conclusion restates the fundamental agreement between the controlling themes of these novels and the tenets of the absurd delineated by Camus. Also, it demonstrates the diversity of method and approach by which the two novels deal with common themes and arrive at affirmative conclusions. Finally, it warns against the interpretation of this fiction as the expression of a doctrine for universal salvation. The Absurd Novel is not, therefore, what Camus would call disparagingly a "thesis-novel" ; at most, like The Myth of Sisyphus, it issues a positive challenge to the individual in the modem world. / Arts, Faculty of / English, Department of / Graduate

No description available.

Spektralradiometermessungen (spektrale optische Dicke und Himmelshelligkeitsfunktion) unter Hochgebirgsbedingungen (Zugspitze, 2965 m) wurden zur Bestimmung der klirnarelevanten Aerosolparameter des stratosphärischen Vulkanaerosols (speziell des Pinatubo) verwendet. Die erhaltenen klirnarelevanten Aerosolparameter aus den Meßkampagnen werden mit Angaben der Aerosolklimatologien verglichen und zur Abschätzung des kurzwelligen Strahlungsforcings durch das Pinatubo-Aerosol verwendet. / Spectral radiometer measurements (spectral optical thickness and sky brightness function) under high mountain conditions (Zugspitze, 2965 m) have been used for the determination of climate-relevant aerosol parameters of the stratospheric volcanic aerosol (columnar size distribution, refractive index, phase function and asymmetry parameter - especially of the aerosol of the Pinatubo volcano eruption in 1991). The climate-relevant aerosol parameters of the measurement campaigns and their temporal change have been compared with data of the aerosol climatologies and have been used for the estimation of the short wave radiative forcing of the Pinatubo event.

In this study, connections between chemical composition, eruption style, and topographic features of two shield volcanoes on the Snake River Plain, Idaho are examined. These relationships may then be applied to understanding silicate volcanic features throughout the inner solar system. Despite their similar ages and geographic locations, two young basaltic shield volcanoes—Kimama Butte (87 Ka) and Rocky Butte (95 Ka)—have strikingly different topographic profiles. The Kimama Butte shield has a diameter of 9 km and a height of 210 m. In contrast, Rocky Butte has a broad 36 km topographic shield that rises 140 m with less than 1° slopes. The vent crater at Rocky Butte developed as a large lava blister inflated and then collapsed forming a crater in which a lava lake developed. Little spatter accumulated throughout the eruption. In contrast, high spatter mounds and spatter-fed flows flank the main summit crater at Kimama Butte. Major- and trace-element compositions of the basaltic lavas are similar at the two shields, but distinct in Ni and Al2O3. The lavas range in TiO2 concentrations from 2.6–4.5 wt.% for Kimama Butte and 2.6–4.3 wt.% for Rocky Butte. These ranges can be related to magma evolution by fractional crystallization involving plagioclase and olivine without clinopyroxene. Compositions of the pre-eruptive phenocrysts are also similar at both shields but show variation with evolution. Olivine cores in the more primitive lavas are more Mg-rich (Fo80-72) than those in the evolved rocks (Fo65-55). Plagioclase cores are similarly more calcic in the more primitive flows (An78-68) than in the evolved ones (An65-52). Like other olivine-tholeiites on the Snake River Plain, the fO2 and fH2O were probably low with fO2 at -2△QFM and 0.1 wt.% H2O. Pressure of crystallization estimated from MELTS models is less than 3 kbar (~10 km deep). Calculated temperatures and magma viscosities overlap at both Kimama Butte (1226 to1147°C and 158 to14 Pa·s) and Rocky Butte (1251 to 1145°C and 75 to 8 Pa·s). However, Kimama Butte magma viscosities extend ~80 Pa·s higher than those for Rocky Butte lavas. The higher magma viscosities are the result of higher phenocryst proportions in spatter and spatter-fed lavas concentrated near the vent. Because lava temperature, volatile content, and chemical composition overlap at the two volcanoes, they are probably not important controls of shield-volcano morphology. This suggests that steep-capped shields are not created as a simple function of having more silicic lavas. Melt viscosities are also similar, but Rocky Butte lacks the phenocryst-rich (>30 vol %), higher magma viscosity lavas and the high spatter ramparts that form the cap at Kimama Butte. Thus, we conclude that eruption style and phenocryst content play the most important role in developing a low-shield volcano summit. Where eruptions shifted from lava lake overflow and tube development to late fountaining with short spatter-fed phenocryst-rich flows, steeper, higher shields develop.

A common concern about volcanic unrest is that the communication of information about increasing volcanic alert levels (VALs) to the public could cause serious social and economic impacts even if an eruption does not occur. To test this statement, this study examined housing prices and business patterns from 1974–2016 in volcanic regions with “very-high” threat designations from the U.S. Geological Survey (USGS)—Long Valley Caldera (LVC), CA (caldera); Mount St. Helens (MSH), Washington (stratovolcano); and Kīlauea, Hawaiʻi (shield volcano). To compare economic trends in nonvolcanic regions that are economically dependent on tourism, Steamboat Springs, CO, served as a control as it is a ski-tourism community much like Mammoth Lakes in LVC. Autoregressive distributed lag (ARDL) models predicted that housing prices were negatively affected by VALs at LVC from 1982–1983 and 1991–1997. While VALs associated with unrest and eruptions included in this study both had short-term indirect effects on housing prices and business indicators (e.g., number of establishments, employment, and salary), these notifications were not strong predictors of long-term economic trends. Our findings suggest that these indirect effects result from both eruptions with higher level VALs and from unrest involving lower-level VAL notifications that communicate a change in volcanic activity but do not indicate that an eruption is imminent or underway. This provides evidence concerning a systemic issue in disaster resilience. While disaster relief is provided by the U.S. federal government for direct impacts associated with disaster events that result in presidential major disaster declarations, there is limited or no assistance for indirect effects to businesses and homeowners that may follow volcanic unrest with no resulting direct physical losses. The fact that periods of volcanic unrest preceding eruption are often protracted in comparison to precursory periods for other hazardous events (e.g., earthquakes, hurricanes, flooding) makes the issue of indirect effects particularly important in regions susceptible to volcanic activity.