Le Merapi est un volcan qui a une actvité quasi-continue, L'explosion est normalement accompagnée par une série de nuées ardentes,edites merapienncs. La chronologie d'activité volcanique varie d'une activité à l'autre, il est donc difficile de trouver le niveau d'activité sismique critique pour ce volcan, En principe, il y a 2 types d'activité: avec et sans séismes volcanotectoniques de types VTA et VTB. Les données de séismes de types VTA et VTB récoltées au courant de l'année 1991 qui ont servi à cette etude, ont fait l'objet d'un traitement de routine (dépouillement, localisation de l'hypocentre, ... ), Ce traitement nous a conduit à remarquer que les séismes de type VTA et ceux de VTB sont séparés par une zone asismique à environ 1.5 km de profondeur. Ce résultat et ceIui de l'analyse pétrographique (Berthommier et al., 1992) conduisent à l'hypothèse de l'existence d'une poche magmatique à cette profondeur. Parmi les séismes de type VTB, nous avons trouvé certains de forme similaire, que l'on appelle doublets ou multiplets. En analysant la variation du délai le long du sismogramme, en utilisant la méthode inter-spectrale de la fenêtre mobile, nous avons constaté que la vitesse sismique a augmenté d'environ 1, 7 % de janvier à septembre 1991. Cette valeur est de l'ordre de dix fois celle observée sur la région tectonique. L'augmentation de vitesse est générée par la croissance de la pression du magma avant l'éruption. La surveillance de la formation du dôme de 1994 a montré que, au bout d'un moment, le processus s'arrête. Nous supposons que ceci est dû à l'équilibre qui s'établit entre la pression du magma à l'extrémité du conduit et la pression lithostatique que génère le dôme, lui-même. Si cel équilibre quasi-stable est interrompu,l'explosion se produit comme celle du 22 novembre 1994.

Aufgrund seiner nahezu kontinuierlichen eruptiven Aktivität zählt der Merapi zu den gefährlichsten Vulkanen der Welt. Der Merapi befindet sich im Zentralteil der dicht bevölkerten Insel Java (Indonesien). Selbst kleinere Ausbrüche des Merapi stellen deswegen eine große Gefahr für die ansässige Bevölkerung in der Umgebung des Vulkans dar. Die am Merapi beobachtete enge Korrelation zwischen seismischer und vulkanischer Aktivität erlaubt es, mit Hilfe der Überwachung der seismischen Aktivität Veränderungen des Aktivitätszustandes des Merapi zu erkennen. Ein System zur automatischen Detektion und Klassifizierung seismischer Ereignisse liefert einen wichtigen Beitrag für die schnelle Analyse der seismischen Aktivität. Im Falle eines bevorstehenden Ausbruchszyklus bedeutet dies ein wichtiges Hilfsmittel für die vor Ort ansässigen Wissenschaftler.<br /> In der vorliegenden Arbeit wird ein Mustererkennungsverfahren verwendet, um die Detektion und Klassifizierung seismischer Signale vulkanischen Urprunges aus den kontinuierlich aufgezeichneten Daten in Echtzeit zu bewerkstelligen. Der hier verwendete A nsatz der hidden Markov Modelle (HMM) wird motiviert durch die große Ähnlichkeit von seismischen Signalen vulkanischen Ursprunges und Sprachaufzeichnungen und den großen Erfolg, den HMM-basierte Erkennungssysteme in der automatischen Spracherkennung erlangt haben. <br /> Für eine erfolgreiche Implementierung eines Mustererkennungssytems ist es notwendig, eine geeignete Parametrisierung der Rohdaten vorzunehmen. Basierend auf den Erfahrungswerten seismologischer Observatorien wird ein Vorgehen zur Parametrisierung des seismischen Wellenfeldes auf Grundlage von robusten Analyseverfahren vorgeschlagen. Die Wellenfeldparameter werden pro Zeitschritt in einen reell-wertigen Mustervektor zusammengefasst. Die aus diesen Mustervektoren gebildete Zeitreihe ist dann Gegenstand des HMM-basierten Erkennungssystems. Um diskrete hidden Markov Modelle (DHMM) verwenden zu können, werden die Mustervektoren durch eine lineare Transformation und nachgeschaltete Vektor Quantisierung in eine diskrete Symbolsequenz überführt. Als Klassifikator kommt eine Maximum-Likelihood Testfunktion zwischen dieser Sequenz und den, in einem überwachten Lernverfahren trainierten, DHMMs zum Einsatz.<br /> Die am Merapi kontinuierlich aufgezeichneten seismischen Daten im Zeitraum vom 01.07. und 05.07.1998 sind besonders für einen Test dieses Klassifikationssystems geeignet. In dieser Zeit zeigte der Merapi einen rapiden Anstieg der Seismizität kurz bevor dem Auftreten zweier Eruptionen am 10.07. und 19.07.1998. Drei der bekannten, vom Vulkanologischen Dienst in Indonesien beschriebenen, seimischen Signalklassen konnten in diesem Zeitraum beobachtet werden. Es handelt sich hierbei um flache vulkanisch-tektonische Beben (VTB, h < 2.5 km), um sogenannte MP-Ereignisse, die in direktem Zusammenhang mit dem Wachstum des aktiven Lavadoms gebracht werden, und um seismische Ereignisse, die durch Gesteinslawinen erzeugt werden (lokaler Name: Guguran).<br /> Die spezielle Geometrie des digitalen seismischen Netzwerkes am Merapi besteht aus einer Kombination von drei Mini-Arrays an den Flanken des Merapi. Für die Parametrisierung des Wellenfeldes werden deswegen seismische Array-Verfahren eingesetzt. Die individuellen Wellenfeld Parameter wurden hinsichtlich ihrer Relevanz für den Klassifikationsprozess detailliert analysiert. Für jede der drei Signalklassen wurde ein Satz von DHMMs trainiert. Zusätzlich wurden als Ausschlussklassen noch zwei Gruppen von Noise-Modellen unterschieden.<br /> Insgesamt konnte mit diesem Ansatz eine Erkennungsrate von 67 % erreicht werden. Im Mittel erzeugte das automatische Klassifizierungssystem 41 Fehlalarme pro Tag und Klasse. Die Güte der Klassifikationsergebnisse zeigt starke Variationen zwischen den individuellen Signalklassen. Flache vulkanisch-tektonische Beben (VTB) zeigen sehr ausgeprägte Wellenfeldeigenschaften und, zumindest im untersuchten Zeitraum, sehr stabile Zeitmuster der individuellen Wellenfeldparameter. Das DHMM-basierte Klassifizierungssystem erlaubte für diesen Ereignistyp nahezu 89% richtige Entscheidungen und erzeugte im Mittel 2 Fehlalarme pro Tag.<br /> Ereignisse der Klassen MP und Guguran sind mit dem automatischen System schwieriger zu erkennen. 64% aller MP-Ereignisse und 74% aller Guguran-Ereignisse wurden korrekt erkannt. Im Mittel kam es bei MP-Ereignissen zu 87 Fehlalarmen und bei Guguran Ereignissen zu 33 Fehlalarmen pro Tag. Eine Vielzahl der Fehlalarme und nicht detektierten Ereignisse entstehen jedoch durch eine Verwechslung dieser beiden Signalklassen im automatischen Erkennnungsprozess. Dieses Ergebnis konnte aufgrund der ähnlichen Wellenfeldeigenschaften beider Signalklassen erklärt werden, deren Ursache vermutlich in den bekannt starken Einflüssen des Mediums entlang des Wellenausbreitungsweges in vulkanischen Gebieten liegen. <br /> Insgesamt ist die Erkennungsleistung des entwickelten automatischen Klassifizierungssystems als sehr vielversprechend einzustufen. Im Gegensatz zu Standardverfahren, bei denen in der Seismologie üblicherweise nur der Startzeitpunkt eines seismischen Ereignisses detektiert wird, werden in dem untersuchten Verfahren seismische Ereignisse in ihrer Gesamtheit erfasst und zudem im selben Schritt bereits klassifiziert. / Merapi volcano is one of the most active and dangerous volcanoes of the earth. Located in central part of Java island (Indonesia), even a moderate eruption of Merapi poses a high risk to the highly populated area. Due to the close relationship between the volcanic unrest and the occurrence of seismic events at Mt. Merapi, the monitoring of Merapi's seismicity plays an important role for recognizing major changes in the volcanic activity. An automatic seismic event detection and classification system, which is capable to characterize the actual seismic activity in near real-time, is an important tool which allows the scientists in charge to take immediate decisions during a volcanic crisis. <br /> In order to accomplish the task of detecting and classifying volcano-seismic signals automatically in the continuous data streams, a pattern recognition approach has been used. It is based on the method of hidden Markov models (HMM), a technique, which has proven to provide high recognition rates at high confidence levels in classification tasks of similar complexity (e.g. speech recognition). Any pattern recognition system relies on the appropriate representation of the input data in order to allow a reasonable class-decision by means of a mathematical test function. Based on the experiences from seismological observatory practice, a parametrization scheme of the seismic waveform data is derived using robust seismological analysis techniques. The wavefield parameters are summarized into a real-valued feature vector per time step. The time series of this feature vector build the basis for the HMM-based classification system. In order to make use of discrete hidden Markov (DHMM) techniques, the feature vectors are further processed by applying a de-correlating and prewhitening transformation and additional vector quantization. The seismic wavefield is finally represented as a discrete symbol sequence with a finite alphabet. This sequence is subject to a maximum likelihood test against the discrete hidden Markov models, learned from a representative set of training sequences for each seismic event type of interest.<br /> A time period from July, 1st to July, 5th, 1998 of rapidly increasing seismic activity prior to the eruptive cycle between July, 10th and July, 19th, 1998 at Merapi volcano is selected for evaluating the performance of this classification approach. Three distinct types of seismic events according to the established classification scheme of the Volcanological Survey of Indonesia (VSI) have been observed during this time period. Shallow volcano-tectonic events VTB (h < 2.5 km), very shallow dome-growth related seismic events MP (h < 1 km) and seismic signals connected to rockfall activity originating from the active lava dome, termed Guguran.<br /> The special configuration of the digital seismic station network at Merapi volcano, a combination of small-aperture array deployments surrounding Merapi's summit region, allows the use of array methods to parametrize the continuously recorded seismic wavefield. The individual signal parameters are analyzed to determine their relevance for the discrimination of seismic event classes. For each of the three observed event types a set of DHMMs has been trained using a selected set of seismic events with varying signal to noise ratios and signal durations. Additionally, two sets of discrete hidden Markov models have been derived for the seismic noise, incorporating the fact, that the wavefield properties of the ambient vibrations differ considerably during working hours and night time. <br /> A total recognition accuracy of 67% is obtained. The mean false alarm (FA) rate can be given by 41 FA/class/day. However, variations in the recognition capabilities for the individual seismic event classes are significant. Shallow volcano-tectonic signals (VTB) show very distinct wavefield properties and (at least in the selected time period) a stable time pattern of wavefield attributes. The DHMM-based classification performs therefore best for VTB-type events, with almost 89% recognition accuracy and 2 FA/day. <br /> Seismic signals of the MP- and Guguran-classes are more difficult to detect and classify. Around 64% of MP-events and 74% of Guguran signals are recognized correctly. The average false alarm rate for MP-events is 87 FA/day, whereas for Guguran signals 33 FA/day are obtained. However, the majority of missed events and false alarms for both MP and Guguran events are due to confusion errors between these two event classes in the recognition process. <br /> The confusion of MP and Guguran events is interpreted as being a consequence of the selected parametrization approach for the continuous seismic data streams. The observed patterns of the analyzed wavefield attributes for MP and Guguran events show a significant amount of similarity, thus providing not sufficient discriminative information for the numerical classification. The similarity of wavefield parameters obtained for seismic events of MP and Guguran type reflect the commonly observed dominance of path effects on the seismic wave propagation in volcanic environments.<br /> The recognition rates obtained for the five-day period of increasing seismicity show, that the presented DHMM-based automatic classification system is a promising approach for the difficult task of classifying volcano-seismic signals. Compared to standard signal detection algorithms, the most significant advantage of the discussed technique is, that the entire seismogram is detected and classified in a single step.

The psychosocial well-being of survivors of armed conflicts, forced displacement, and/or natural disasters is becoming more and more an integral component of holistic humanitarian response. Yet many organisations rely on broad, generalised manuals or guidelines which do not take into account the unique characteristics of societies and target populations. This paper describes the author’s research with disaster survivors in Java, Indonesia, and refugee in Sweden, aiming to characterise the process of recovery, adaptation and integration through beneficiaries’ own words. The author looks at how theory can be applied, such as whether a hierarchy of needs can be universally relevant, how the host Swedish society affects refugees’ experiences, which so-called “states of being” subjects experience, and how religion and cultural differences like individualism and collectivism influence one’s ability to regain psychosocial well-being. The author used both in-depth interviews and quantitative questionnaires to obtain data. Results showed an incredible level of resilience and positivity among all groups, though Indonesians reported family, spirituality and the community as major helping factors, while many refugees in Sweden pointed to their own individual determination and will to succeed. Many Indonesians identified economic livelihood as the biggest remaining gap, while refugees in Sweden spoke of language skills, educational qualifications and employment as keys to success and integration. Many challenges and gaps remain, especially for newly arrived refugees facing an increasingly difficult job market and fewer opportunities.

This thesis attempts to develop our understanding of volcanic magma plumbing systems and the magmatic processes that operate within them, such as fractional crystallisation, crustal partial melting, assimilation, and magma mixing. I utilise petrology, rock and mineral geochemistry, and isotope systematics to seek to improve our ability to forecast the eruptive frequency and style of active volcanoes, an aspect often lacking in current volcano monitoring efforts. In particular, magma reservoir dynamics are investigated from a mineral scale at Katla volcano in Iceland, to a sub-mineral scale at Merapi, Kelud, and Toba volcanoes in Indonesia. The magma plumbing architecture of Katla volcano on Iceland is explored in the first part of this thesis. Crystalline components within tephra and volcanic rock preserve a record of the physical and chemical evolution of a magma, and are analysed through oxygen isotopic and thermobarometric techniques to temporally constrain changes in reservoir depth and decode the petrogenesis of the lavas. We find both prolonged upper crustal magma storage and shallow level assimilation to be occurring at Katla. The results generated from combining these analytical strands reveal the potential for unpredictable explosive volcanism at this lively Icelandic volcano. The second part of this thesis examines the magma plumbing systems of Merapi, Kelud and Toba volcanoes of the Sunda arc in Indonesia at higher temporal and petrological resolution than possible for Katla (e.g., due to the crystal poor character of the rocks). For this part of the thesis, minerals were analysed in-situ to take advantage of sub-crystal scale isotopic variations in order to investigate processes of shallow-level assimilation in the build-up to particular eruptions. We find that intra-crystal analyses reveal an otherwise hidden differentiation history at these volcanoes, and establish a better understanding as to how they may have rapidly achieved a critical explosive state. The outcomes of this thesis therefore deepen our knowledge of evolutionary trends in magma plumbing system dynamics, and highlight the importance of understanding the geochemical processes that can prime a volcano for eruption. Lastly, I emphasise the vital contribution petrology can make in current volcano monitoring efforts.

Les connaissances actuelles sur le comportement hydrogéologique des édifices volcano-détritique sont encore limitées et cela limite la bonne gestion des ressources en eau. Depuis une décennie, sur les flancs du volcan Merapi, à Java Centre, en Indonésie, une pression croissante se fait sur la ressource en eau avec l'intensification des pratiques agricoles irriguées, la croissance de la population et les utilisations industrielles de l'eau. Le manque de connaissances sur les processus du cycle de l'eau par les consommateurs déclenche des conflits d'usage et le partage de l'eau devient une question centrale. Une compréhension plus précise du cycle de l'eau dans sa globalité dans ce genre de contexte est donc un point fondamental qui a besoin d'être amélioré.Ce travail a été axé sur la caractérisation des ressources en eaux souterraines à travers l’étude de la géométrie et des propriétés hydrodynamiques des systèmes aquifères /aquitards multi-couches à l'échelle d’un bassin versant expérimental sur le flanc Est du volcan Merapi. Pour couvrir tous les processus impliqués dans la circulation des eaux souterraines, une approche multi-disciplinaire a été choisi.Une nouvelle approche géologique et géomorphologique a été réalisé afin de caractériser la structure interne et l'architecture de dépôt sur le flanc Est du Merapi. Sur la base de ces résultats, un modèle conceptuel géologique et géomorphologique a été construit et révèle des formations détritiques chenalisées et connectées depuis les hautes altitudes jusqu’aux vallées, créant des chemins préférentiels pour les eaux souterraines.La caractérisation du climat avec l'estimation des termes du bilan hydrique et la description des principaux processus hydrologiques sont décrits par le suivi de deux années hydrologiques (2011-2012 et 2012-2013 ). Le climat tropical de cette région se caractérise par une période de mousson (Novembre à Mai ) et une saison sèche (Juin à Octobre ). Le bilan hydrologique est caractérisé par 40 % des précipitations sont perdus par évapotranspiration, 10 % s'écoulent et la moitié restante s'infiltre à travers l'édifice volcano-détritique et recharge les aquifères multicouches.Le fonctionnement hydrogéologique d'un environnement volcano-détritique complexe a pu être appréhendé à l’aide d’un suivi hydrogéologique, hydrochimique et géochimiques sur les sources et des puits peu profonds. Deux ceintures de sources ont été identifiées: la première est caractérisée par des sources de dépression alignées le long d'une ligne topographique tandis qu'une faille normale est probablement à l'origine de la seconde. L’utilisation de la température de l’eau de source comme traceur de l’altitude de recharge a permis l’identification de plusieurs systèmes aquifères multi-couches. Les propriétés hydrauliques de ces aquifères ont été établi à partir des l'analyses des essais hydrauliques. Le premier système aquifère est situé proche de la surface et possède une faible conductivité hydraulique. En revanche, un second système aquifère a été identifié en profondeur et possède une forte perméabilité. Le traceur “température” met en évidence un effet de mélange entre le premier et le deuxième aquifère au niveau des sources de basses altitudes . Ce phénomène est confirmé par les résultats des analyses isotopiques.L'application d'un modèle numérique couplant la circulation des flux, le transfert de masse ou le transfert de chaleur confirme le modèle conceptuel hydrogéologique et permet de quantifier la ressource en eau. / The current knowledge on the hydrogeological behavior of the volcano-detritic edifices is still sparse and these lacks limit the attempting of water resource management. Since a decade, on the flanks of Merapi volcano, in Central Java, Indonesia, an increasing pressure is done on the water resource with the intensification of the irrigated agriculture practices, the growth of population and the water industrial uses. The lack of knowledge about the water cycle processes by the consumers triggers water use conflicts and the water sharing becomes a central issue. A most accurate understanding of the water cycle in its globality in this kind of context is hence a fundamental point that need to be improved.This work has been focused on the characterization of groundwater resource thought the identification of the extent, the geometry and hydrodynamic properties of the aquifers/aquitards multi-layered system at the experimental catchment scale on the Eastern flank of Merapi volcano. To cover all the processes involved into the groundwater circulation, a multi-disciplinary approach has been chosen.A new geological and geomorphological approach is performed to characterize the internal structure and the deposit architecture on this zone of the Eastern flank of the Merapi. Based on these results, a geological and geomorphological conceptual model has been built and insists on the channelized detritic formations connected from the upper parts to the low lands through the volcanic edifice and that create preferential groundwater path ways.The climate characterization with the estimation of the water balance terms and the description of main hydrological processes are described with the monitoring of two hydrological years (2011-2012 and 2012- 2013). The tropical climate of this region is characterized by seasonal monsoon (November to May) and dry season (June to October). The global water balance can be distributed as follow: 40% of rainfall are lost by evapotranspiration, 10% runs off and the remaining half infiltrates through the volcano-detritic edifice to recharge the multi-layered aquifers.The hydrogeological functioning of a complex volcano-detritic environment is explained through the implementation of hydrogeological, hydrochemical and geochemical monitoring on inventoried springs and wells. Two spring belts are described, the first one is characterized by depression spring along a topographic line while a normal fault is probably at the origin of the second one. The identification of a multi-layered aquifer systems has been done based on the determination of the spring water temperature as a relevant tracers of the recharge elevation and the groundwater circulations. The hydraulic properties of these aquifers have been investigated from the analysis of hydraulic tests. Results show a low permeable aquifer close to the surface with a local recharge while a second aquifer system with high permeability and regional recharge is located deeper. The tracer temperature shows a mixing effect between the first and the second aquifers in the springs at low elevation. This phenomenon is confirmed by the isotope analysis.The application of a coupled numerical model between flow circulation, first mass transfer and second heat transfer confirms the hydrogeological conceptual model of volcano-sedimentary edifice and allows to quantify the water resource.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21330号 / 理博第4426号 / 新制||理||1636(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 井口 正人, 教授 福田 洋一, 教授 大倉 敬宏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

One of the most important volatiles in magma is water. In magma, water is incorporated in both the melt and in crystals, including hydrous and nominally anhydrous minerals (NAMs). The purpose of this study is to determine the role of magmatic water content in controlling volcano explosivity especially at Merapi volcano, Indonesia, which is one of the most active volcanoes in the world. Here I apply clinopyroxene from two types of eruption products, lava and ash, to test the magmatic water content in the Merapi 2010 eruption. Both oriented and unoriented crystals were analysed using Fourier-Transformed Infrared (FTIR) spectroscopy to establish the clinopyroxene’s crystal water content. By combining the water content of clinopyroxene and geochemical data obtained from EPMA analysis, the magmatic water content is then estimated by inserting the data into the equation of O’Leary et al. (2010) [lnD= -4.2(60.2)16.5(60.5) VI[Al3+]-1.0(60.2) [Ca2+]]. I also investigated clinopyroxene crystals that were experimentally rehydrated, including four oriented crystals from a Merapi 2010 eruption ash sample annealed at a temperature of 700°C and pressure of 1 atm. Magmatic water contents of Merapi 2010 from rehydration experiments were then compared to the Merapi 2006 magmatic water content which were treated under the same conditions. The results revealed a wide variation between samples and among crystals taken from the same sample. However, oriented samples yielded a smaller variation between minimum and maximum clinopyroxene crystal water content and, overall, ash samples yielded higher water content in clinopyroxene than lava samples. The rehydration experiment significantly amplified clinopyroxene crystal water content by 3 to 7-fold compared to the result without the rehydration procedure. Comparison of data between the 2006 and 2010 Merapi eruptions demonstrates that there was a significant difference in magmatic water contents with the 2010 eruption displaying more than twice as much magmatic water than the 2006 eruption. The result implies that magmatic water plays potentially a crucial role in controlling explosivity of Merapi eruptions. / Indonesien är det land i Världen som har den största befolkningen som lever inom 100 km av en aktiv vulkan. Merapi är en av de mest farliga vulkanerna i Indonesien, som också är en av de mest aktiva vulkanerna i Världen och ligger på ön Java runt 15-25 km från Yogyakarta med en total befolkningstäthet på 1000 personer per kvadratkilometer. Utbrott från Merapi har dödat cirka 5000 personer under de senaste 500 åren. Således är det viktigt att studera hur vulkanen beter sig och orsaken till utbrotten för att kunna vita förebyggande åtgärder för att minska antalet dödsfall eller till och med undvika dödsfall helt. Vulkanutbrott kontrolleras av många faktorer, en av faktorerna är flyktiga ämnen i magman och en av de viktigaste flyktiga ämnen är vatten. Det här projektet syftar till att ta reda på vattnets roll på explosiviteten hos utbrotten genom att undersöka eruptiva produkter från utbrotten av Merapi under 2006 och 2010 med hjälp av Fourier-Transformed Infrared (FTIR) spektroskopi. Experimentet använder normalt vattenfria mineraler (NAMs) så som klinopyroxen men vatten kan införlivas i NAMs genom att binda väte i kristallgitteret under kristalltillväxten. Tidigare studier har visat att vattenhalten i klinopyroxenkristall skulle kunna användas för att beräkna magmatisk vattenhalt och därmed jämföra den magmatiska vattenhalt mellan olika utbrott med olika explosivitet i samma vulkan, vilket kan indikera hur vattenhalten påverkar vulkanutbrotten. Magmatiskt vatteninnehåll beräknat utifrån klinopyroxenvattenhalten visade en variation mellan de undersöka proverna från samma utbrott, varför ytterligare undersökning genom rehydreringsexperiment gjordes genom annealing av proverna vid en temperatur av 700 °C och tryck vid 1 atm. Även om det var variation i magmatisk vattenhalt mellan proverna, så har utbrotten av Merapi under 2010 högre magmatiskt vatteninnehåll än utbrottet under 2006 med 3-7 gånger. Sammantaget har Merapi 2010 utbrottet högre explosivitet och högre magmatisk vattenhalt än 2006 utbrottet, vilket innebär att högre vattenhalt ger högre explosivitet. På detta sätt kontrollerade vattnet vulkanens explosivitet för Merapivulkanen.Nyckelord: Merapi vulkan, NA

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La transition entre le comportement effusif et explosif des volcans de magma riche en silice est en partie contrôlée par la capacité des surpressions gazeuses à se dissiper hors du magma. La libération efficace des gaz est associée aux éruptions effusives tandis que la rétention de ces gaz contribue aux processus explosifs. L’une des approches pour évaluer la facilité d’échappement des gaz est de considérer l’évolution et le développement de la perméabilité dans la colonne magmatique et dans l'édifice. J'évalue dans ce travail de thèse le rôle des changements post-mise en place sur la microstructure dans des andésites basaltiques du Merapi (Indonésie). La perméabilité de ces roches est principalement contrôlée par des fissures liées à leur mise en place. Malgré l’influence importante de ces fissures post-mise en place pour dégazer à travers l'édifice, elles ne contribuent pas au dégazage intrinsique du magma en cours d’ascension. Pour s’affranchir de l'influence des microstructures post-mise en place du magma, j'étudie le développement et l'évolution in situ des réseaux perméables en déformant des magmas à deux phases (bulles de gaz et liquide silicaté) en cisaillement simple dans une presse Paterson selon des viscosités et des vitesses de déformation réalistes pour la partie haute des conduits des strato-volcans. Le développement de la perméabilité est confirmé in situ et se développe à des vitesses de déformation supérieures à 4,5 x 10⁻⁴ s⁻¹. À des vitesses de déformation élevées (> 5 x 10⁻⁴ s⁻¹) le magma est fragile et l’échappement du gaz est lente, facilitée par l'interconnexion de courtes fractures de Mode I. À des vitesses de déformation < 5 × 10⁻⁴ s⁻¹, le magma se comporte à la fois de manière fragile et visqueuse et la perméabilité se développe lorsque la déformation est importante; le gaz s’échappe rapidement par de longues fractures de Mode I bien développées. Les fractures de Mode I sont idéalement orientées pour le dégazage du conduit central et sont, surtout, soumises à peu de déformation jusqu'à ce qu'elles soient réorientées dans la direction de cisaillement. Ces caractéristiques de dégazage peuvent, à long terme, favoriser un dynamisme éruptif effussif. / The transition from effusive to explosive behaviour at silicic volcanoes is, in part, governed by how efficiently gas overpressures are dissipated from the volcanic plumbing. Efficient gas release is associated with effusive eruptions while inadequate outgassing contributes to explosive processes. One approach to assessing the facility of gas escape is by considering how permeability develops and evolves in the magma column and surrounding edifice. Here, I appraise the role of post-emplacement changes to microstructure in edifice-forming basaltic andesites from Merapi (Indonesia). The permeability of these rocks is dominantly crack-controlled and while these features exert important controls on gas escape through the edifice, they do not represent the escape pathways available to gas within ascending magma. To avoid the influence of postemplacement microstructure, I investigate the development and evolution of permeable networks in magmas by deforming initially impermeable two-phase magmas in simple shear. This is done in a Paterson apparatus at viscosities and shear strain rates appropriate to upper conduits in stratovolcanoes. Permeability development is confirmed in situ and develops at moderate to high shear strain rates (> 4.5 × 10⁻⁴ s⁻¹). At very high strain rates (> 5 × 10⁻⁴ s⁻¹) the magma behaves in a brittle manner and gas egress is slow, facilitated by the interconnection of short, Mode I fractures. At moderate shear strain rates (< 5 × 10⁻⁴ s⁻¹), the magma displays both brittle and viscous behaviour and permeability develops at high strain; gas escape is rapid owing to long, well-developed, sample-length Mode I fractures. Mode I fractures are ideally oriented for outgassing of the central conduit and, critically, accommodate little deformation until they are rotated into the direction of shear, making them long-lived outgassing features that may favour volcanic effusion.

The focus of this work is magma-crust interaction processes and associated crustal volatile release in subduction zone volcanoes, drawing on rock, mineral, and gas geochemistry as well as experimental petrology. Understanding the multitude of differentiation processes that modify an original magma during ascent to the surface is vital to unravel the contributions of the various sources that contribute to the final magmas erupted at volcanoes. In particular, magma-crust interaction (MCI) processes have been investigated at a variety of scales, from a local scale in the Vesuvius, Merapi, and Kelut studies, to a regional scale, in the Java to Bali segment of the Sunda Arc.  The role of crustal influences is still not well constrained in subduction systems, particulary in terms of the compositional impact of direct magma crust interplay. To address this shortcoming, we studied marble and calc-silicate (skarn) xenoliths, and used high resolution short timescale experimental petrology at Vesuvius volcano. The marbles and calc-silicates help to identify different mechanisms of magma-carbonate and magma-xenolith interaction, and the subsequent effects of volatile release on potential eruptive behaviour, while sequential short-duration experiments simulate the actual processes of carbonate assimilation employing natural materials and controlled magmatic conditions. The experiments highlight the efficiency of carbonate assimilation and associated carbonate-derived CO2 liberated over short timescales. The findings at Merapi and Kelut demonstrate a complex magmatic plumbing system underneath these volcanoes with magma residing at different depths, spanning from the mantle-crust boundary to the upper crust. The erupted products and volcanic gas emissions enable us to shed light on MCI-processes and associated volatile release in these systems. The knowledge gained from studying individual volcanoes (e.g., Merapi and Kelut) is then tested on a regional scale and applied to the entire Java and Bali arc segment. An attempt is presented to distinguish the extent of source versus crustal influences and establish a quantitative model of late stage crustal influence in this arc segment. This thesis therefore hopes to contribute to our knowledge of magma genesis and magma-crust interaction (MCI) processes that likely operate in subduction zone systems worldwide.