In the last years, geodetic measurements have shown that temporal variations in total groundwater content induce transient deformations of the crust that are mostly reflected in the vertical component. Here we present new GPS observations showing a noticeable non-tectonic transient deformation in the Apennines (Italy), mostly evident in the horizontal components, that correlate with multi-annual hydrological signals as measured by rainfall, GRACE (Gravity Recovery and Climate Experiment) and discharge of karst springs. The observed transient signal is superimposed on the long-term ~3mm/yr NE-SW directed active extension, correlates with the seasonal recharge/discharge cycle of groundwater flow and its multi-annual variations and appears to modulate the intensity of tectonic extensional opening in those regions characterized by large carbonate aquifers. In particular, periods of increasing discharge from karstic spring correlate with an enhanced extensional signal, whereas exhaustion periods correlate with reduced extensional signal. Vertical observations, being correlated with GRACE data, reflect the hydrological load variation over regional (European) scale. Horizontal deformations, conversely, affect mostly the sites located near the large carbonate massifs of the Apennines and can't be explained as load induced response. We suggest that the horizontal observed deformation is related to the presence of highly fractured shallow crust that deforms according to variable conditions of the hydraulic head within the large carbonate aquifers. We therefore propose two different models that simulates the effect of a medium permeated with sub-vertical opening fractures. These new findings could contribute to the understanding of the deformation of the large carbonate aquifers and to an improved management of these important natural resources. By focusing on the 2009 L'Aquila earthquake, we finally highlight the difficulties that arise for the estimation of interseimic trends and small tectonic signals in areas affected by such significant non-tectonic deformations.

This work focuses on the role of SAR Interferometry (InSAR) in the study of many phenomena characterizing the Earth's surface. We propose an advanced integration method in order to merge the InSAR data with other geodetic data, i.e. Multiple Aperture Interferometry (MAI), Pixel Offset Tracking (POT) and Global Positioning System (GPS). We apply the method to constrain the full 3D displacement field produced by the Mw 6.1 2014 South Napa Valley earthquake and then we used the results from the integration to perform the source modeling. The first Chapter is meant to introduce the topic of the progressive use of Remote Sensing geodetic data to support the activities of monitoring and hazard mitigation related to natural phenomena. Chapter 2 shows the application of the InSAR technique to reconstruct and model surface displacement fields induced by several phenomena. In Chapter 3, the 3D coseismic displacement map due to the 2014 Mw 6.1 South Napa earthquake, close the San Andreas Fault system (California), is estimated by using a method to merge InSAR and GPS data. InSAR data are provided by the latest satellite of the European Space Agency (ESA), i.e. Sentinel-1, whereas the GPS data were obtained from the BARD network and several online archives. In Chapter 4 we propose an improved algorithm for the data integration and test it on the Napa earthquake. Geodetic data from MAI and POT are added in the processing chain and the GPS data interpolation is modified according to the specific phenomenon. Futhermore, the source modeling is performed by inversion of the obtained 3D displacement component. The best fit is obtained by simulating a fracture in the fault segment in agreement with previous works. Finally, in the last chapter we discuss about the advantages and disadvantages of the data integration and the future perspectives.

The interaction between earthquakes and crustal fluids is a very complex topic due to several mechanisms that are involved and which influence each other. Some phenomena, like the alterations of springs discharge rates and fluid flow, liquefaction and changing of the water levels in phreatic wells are largely documented in the literature, but their explanation is not yet fully clear. Furthermore, these phenomena can greatly change with the rock type, the earthquake magnitude and the observation distance from the fault. Within a distance of a few fault lengths from the epicenter, an earthquake can alter both the regional stress field and the hydraulic properties of the rocks, influencing the underground fluid distribution. In this thesis, I apply the numerical simulator TOUGH2 to represent the changes in water level of some wells after the ML 5.9 earthquake that took place in Italy in 2012. The model shows that the wells response to the seismic event can be represented imposing a static stress change and highlights the role of the soil stratigraphy. This zone is also well known for localized methane seepages associated with anomalous soil temperatures. I simulate the process and draw some conclusions on the nature of this phenomenon and on the possible interactions with the local seismicity. Finally, I study the earthquake-fluid interaction from the opposite point of view: looking at how fluids can promote seismicity. I present the results obtained by coupling the TOUGH2 geothermal simulator with a stochastic seed model of seismicity. The coupled simulation could capture the main characteristics of the seismicity induced by the fluid injection in a seismically active area. / L'interazione tra terremoti e fluidi crostali è un argomento molto complesso per via dei numerosi meccanismi che sono coinvolti e che si influenzano a vicenda. Alcuni fenomeni, come l'alterazione delle sorgenti e del flusso di fluidi, la liquefazione e il cambiamento del livello d'acqua nei pozzi freatici, sono largamente documentati in letteratura, tuttavia la loro spiegazione non è ancora del tutto chiara. Oltretutto, questi fenomeni possono cambiare sensibilmente in base al tipo di roccia, alla magnitudo del terremoto e alla distanza dalla faglia. Entro una distanza di poche lunghezze di faglia dall'epicentro, un terremoto può modificare sia il campo di sforzo regionale che le proprietà idrauliche della roccia, influenzando la distribuzione dei fluidi nel sottosuolo. In questa tesi utilizzo il simulatore numerico TOUGH2 per rappresentare la variazione del livello d'acqua di alcuni pozzi successivamente al terremoto di magnitudo ML5.9 che avvenne in Italia nel 2012. Il modello mostra che la risposta dei pozzi al terremoto può essere rappresentata imponendo una variazione di stress statico ed evidenzia l'importanza della stratigrafia del sottosuolo. Questa zona è ben nota anche per emissioni di metano localizzate, associate a riscaldamenti anomali del sottosuolo. In questa tesi presento delle simulazioni per rappresentare questo processo e traggo alcune conclusioni circa la natura di questo fenomeno e sulle sue possibili interazioni con la sismicità locale. In ultimo, studio la relazione tra fluidi e terremoto dal punto di vista opposto: come I fluidi possono facilitare la sismicità. Presento i risultati ottenuti accoppiando il simulatore geotermico TOUGH2 con un modello sismico, stocastico, a “seed”. La simulazione accoppiata è in grado di catturare le caratteristiche principali della sismicità indotta dall'iniezione di fluidi in un'area sismicamente attiva.

No description available.

In recent years, thanks to the technological advances, electromagnetic methods for non-invasive shallow subsurface characterization have been increasingly used in many areas of environmental and geoscience applications. Among all the geophysical electromagnetic methods, the Ground Penetrating Radar (GPR) has received unprecedented attention over the last few decades due to its capability to obtain, spatially and temporally, high-resolution electromagnetic parameter information thanks to its versatility, its handling, its non-invasive nature, its high resolving power, and its fast implementation. The main focus of this thesis is to perform a dielectric site characterization in an efficient and accurate way studying in-depth a physical phenomenon behind a recent developed GPR approach, the so-called early-time technique, which infers the electrical properties of the soil in the proximity of the antennas. In particular, the early-time approach is based on the amplitude analysis of the early-time portion of the GPR waveform using a fixed-offset ground-coupled antenna configuration where the separation between the transmitting and receiving antenna is on the order of the dominant pulse-wavelength. Amplitude information can be extracted from the early-time signal through complex trace analysis, computing the instantaneous-amplitude attributes over a selected time-duration of the early-time signal. Basically, if the acquired GPR signals are considered to represent the real part of a complex trace, and the imaginary part is the quadrature component obtained by applying a Hilbert transform to the GPR trace, the amplitude envelope is the absolute value of the resulting complex trace (also known as the instantaneous-amplitude). Analysing laboratory information, numerical simulations and natural field conditions, and summarising the overall results embodied in this thesis, it is possible to suggest the early-time GPR technique as an effective method to estimate physical properties of the soil in a fast and non-invasive way.

The thesis deals with the Dynamo Theories of the Earth’s Magnetic Field and mainly deepens the turbulence phenomena in the fluid Earth’s core. Indeed, we think that these phenomena are very important to understand the recent decay of the geomagnetic field. The thesis concerns also the dynamics of the outer core and some very rapid changes of the geomagnetic field observed in the Earth’s surface and some aspects regarding the (likely) isotropic turbulence in the Magnetohydrodynamics. These topics are related to the Dynamo Theories and could be useful to investigate the geomagnetic field trends.

Aim of this work is the study of the stress field in the Campi Flegrei caldera during the bradyseismic crisis of 1982-1984. n the first part of the work has been analysed old cretaceous and digital seismic datasets relative to 70th years, and the bradyseismic crisis of 1982-1984 where has been recorded the earthquakes linked to uplifts that interested Campi flegrei caldera during 1969-72 and 1982-84. The seismicity dataset has been used to made some analysis as location and focal mechanisms generation. The focal mechanisms are than analysed using two software to determine the principal state of stress that was predominant in that period. Then, starting from ground deformation data, relative to 1100 optical levelling measure done during the bradyseismic crisis, has been use the inversion method to modelling the source of the deformation. Has been used many model as the Mogi model, the penny shaped-crack, and the rectangular crack of Okada. Consequently, a joint inversion was applicate on ground deformation data and seismicity together to better understand the dynamic of the stress in the area.In the last part of the work, has been determined the excess of pore pressure in the Flegrean area, using focal mechanisms to study the influence of fluid pore pressure on change in the Coulomb stress of the area. Has been used the Coulomb-Navier criterion and Terakawa method (2010) to estimate the excess of pore pressure. Finally, in order to evaluate the reliability of the calculated pore pressures, was done thermo-fluid dynamic simulation and analysed the hydrothermal system of Campi Flegrei caldera. So, has been performed a series of simulation thermo-fluid dynamic injecting a flow in the system varying temperature, pressure and injection rate to model the Campi Flegrei caldera during the unrest.

Cette thèse se compose de trois chapitres indépendants abordant différentes questions de l’économie de l’information. Le premier chapitre étudie des stratégies optimales des entreprises qui sont présentes sur les marchés en ligne et hors ligne. Nous étudions des stratégies de prix optimales des détaillants en présence de showrooming et leurs décisions sur des canaux de distribution. Le showrooming est une situation où les consommateurs essayent des produits dans des magasins classiques avant de les acheter en ligne à un prix inférieur. Une manière d’empêcher le showrooming est d’utiliser des prix identiques dans le magasin physique et en ligne. Nous montrons que dans l’optique de recherche de prix bas, le choix de prix identiques est, en effet, un choix optimal. Cependant concernant des prix plus élevés, les prix identiques sont suboptimals, et les achats en ligne et en magasins classiques coexistent avec le showrooming. Une entreprise qui fait face à la concurrence en ligne d’un détaillant multicanaux étranger a une incitation au geo-blocking, c.-à-d. qu’elle refuse de servir les clients étrangers, bien que cela amène à une diminution de la demande. Le geo-blocking modère la concurrence en ligne et mène à des prix plus élevés aussi bien en ligne que dans les magasins physiques. L’exigence juridique des prix identiques, aide à éliminer les incitations au geo-blocking et reconstitue ainsi la concurrence en ligne. Le deuxième chapitre analyse la diffusion de l’information dans les réseaux de la communication où les interactions sociales sont coûteuses. Nous proposons un modèle dynamique avec les agents stratégiques qui décident combien d’effort mettre dans la stratégie publicitaire d’un produit pour une période donnée. Nous montrons que le niveau d’équilibre de l’effort individuel de la communication est convexe avec la proportion des agents avertis, et inférieur le niveau socialement optimal au cause de l’effet substantiel de free-riding. Nous prouvons que pour des coûts de recommandation suffisamment élevées c’est socialement optimal que les agents symétriques exercent le même effort de communication tandis que pour des coûts de recommandation basses ceci n’est pas vrai. Dans le cadre de notre modèle nous analysons la stratégie de la publicité de l’entreprise lançant un nouveau produit avec des extériorités de réseau positives pour des consommateurs. Les expositions d’analyse montrent que les résultats de la publicité diminuent rapidement en proportion de consommateurs avertis de l’effet de free-riding. Ainsi, de façon optimale l’entreprise doit ajuster et réduire le niveau de la publicité par intermittence. Le troisième chapitre est un papier co-écrit avec Maarten Janssen et Alexei Parakhonyak. Dans cet article nous proposons un nouveau concept d’équilibre “Non-reservation price equilibria” (Non-RPE). “Reservation price equilibria” (RPE) n’évaluent pas exactement la puissance du marché dans les marchés de recherche du consommateur. Sur la plupart des marchés de recherche, les consommateurs ne connaissent pas les éléments importants de l’environnement dans lequel ils font des recherches (comme, pour exemple, le coût pour les entreprises). Nous discutons que RPE souffrent de questions théoriques, telles que la non-existence et la dépendance critique des croyances spécifiques hors-de-équilibre, quand les consommateurs apprennent en faisant des recherches. Nous définissons équilibrée, la situation où les consommateurs choisissent rationnellement des stratégies de recherche qui ne sont pas caractérisées par un prix de réservation. Non-RPE existent toujours et ne dépendent pas des croyances spécifiques hors-deéquilibre. Non-RPE ont pour objectif la recherche active du consommateur et sont compatibles avec les résultats empiriques récents. / This thesis consists of three independent chapters addressing different questions of information economics. The first chapter studies optimal strategies of firms which are present in both offline and online markets. We study optimal pricing strategies of retailers in presence of showrooming and their decisions on distribution channels. Showrooming is a situation where consumers try products at brick-and-mortar stores before purchasing them online at a lower price. One way to prevent showrooming is to use a price matching policy, whereby price is the same in both the physical store and the online channel. We show that for small search costs, a price matching policy is indeed optimal. However for higher search costs price matching is suboptimal, and online and offline purchases coexist with showrooming. A firm which faces online competition from a foreign multichannel retailer has an incentive to geo-block, i.e. refuse to serve foreign customers, even though it leads to a decrease in potential demand. Geo-blocking relaxes online competition and leads to higher prices both online and in brick-and-mortar stores. A legal price parity requirement helps to eliminate incentives to geo-block and thus restores online competition. The second chapter analyzes information diffusion process in communication networks where social interactions are costly. We provide a dynamic model with strategic agents who decide how much effort to put into the propagation of information about a product in each period. We show that the equilibrium level of the individual communication effort is convex in the proportion of informed agents, and lower than the socially optimal level due to the substantial free-riding effect. We show that for sufficiently high recommendation cost it is socially optimal that symmetric agents exert the same communication effort while for low recommendation cost this is not true. In the context of our model we analyze the advertising strategy of the firm launching a new product with positive network externalities for consumers. The analysis shows that the outcome of advertisement is decreasing fast with the proportion of informed consumers due to the free-riding effect. Thus, optimally the firm has to adjust and reduce the level of advertising in each period. The third chapter is a co-authored paper with Maarten Janssen and Alexei Parakhonyak. In this paper we propose a new equilibrium concept of Non-reservation price equilibria (Non-RPE). Reservation price equilibria (RPE) do not accurately assess market power in consumer search markets. In most search markets, consumers do not know important elements of the environment in which they search (such as, for example, firms’ cost). We argue that when consumers learn when searching, RPE suffer from theoretical issues, such as non-existence and critical dependence on specific out-of-equilibrium beliefs. We characterize equilibria where consumers rationally choose search strategies that are not characterized by a reservation price. Non-RPE always exist and do not depend on specific out-of-equilibrium beliefs. Non-RPE have active consumer search and are consistent with recent empirical findings.

Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 2010

Decades after 1602, Taiwan was an unique stage for continual showing of power struggles of various great powers. Three ancient concepts, including strategy, political order and history are precisely the main axles connecting these historical events. Each one of these domains would have significant and profound influence interweaved with others. Geographically, Taiwan is not only the center of the first island chain out of the continent, it is also located at the top of this so call ¡§Asiatic Mediterranean¡¨ triangle. The geographical location of Taiwan thus unpreventable made it revolving in the struggles among international powers. The action of a state definitely will aim at its national interest. The foreign policy of a nation would be set according to a guided rule which included the geopolitical code. To be more precise, the geopolitical code is one of the important criteria to identify national interest as well as adversary and to react against them. This research is based on three geological levels, including local level of Taiwan, regional level of Southeast Asia and the global level to analyze the geopolitics of Taiwan and to examine various powers which had ruled Taiwan in the history. In terms of the geography matters, the maritime power disposition, the geopolitics and the geo-economy are factors to shape up the destiny of Taiwan for some 400 years by different powers from the world. In the final analysis, based on a principle that political order would be changed following the changes of stratagem, it shows that the consideration and planning of foreign strategy would have great impact in the domestic political order and administrative policy. In one word, the geological location of Taiwan put it in the cross road of the ocean while geopolitical and economical factors confine Taiwan to be ruled by invasion powers for the last four hundred years.