We carry out non-invasive ambient noise investigation of rock structures in Bohemian Paradise (Bohemian Cretaceous Basin, Czech Republic). The study is focused on two key topics: 1) An in-situ elastic moduli estimate of competent, horizontally deposited sandstone layers. This is done by performing an ambient noise array measurement. The recording is processed with f-k array analysis, from which frequency-dependent Love and Rayleigh wave dispersion curves as well as the Rayleigh wave ellipticity are retrieved. The data are inverted for P- and S-wave velocity profiles, from which the Young's and shear modulus are successfully estimated. 2) Study of local response of Kapelník rock tower. We analyse a dataset of ambient noise recordings from the top of the tower and from its foot. Information about tower oscillation frequencies and directions, together with amplification ratios, are retrieved from particle motion polarisation analysis and from site-to-reference spectral ratios. The Euler-Bernoulli beam theory is finally used to interpret the measured data using the elastic moduli estimated from the noise array measurement. Keywords: Bohemian Paradise, rock tower, seismic ambient noise, seismic surface waves

Background noise is ubiquitous and can impair acoustic communication and influence signaling behavior in animals. Despite evidence demonstrating myriad effects of anthropogenic noise on animal communication, precisely how natural background noise influences communication and behavior remains unclear. Yet, natural sources of background noise, such as rushing rivers or crashing ocean surf, share similar power spectra to sources of anthropogenic noise and can occur at high amplitudes, potentially masking acoustic signals. To investigate the effects of water-generated noise on songbird behavior, we experimentally broadcast landscape-level playbacks of ocean surf and river noise in coastal California, USA, and riparian habitat in Idaho, USA, respectively. In Chapter 1, we conducted a conspecific playback experiment examining how territorial defense behaviors of lazuli buntings (Passerina amoena) and spotted towhees (Pipilo maculatus) vary in response to broadcast water noise. We also incorporated cicada noise from a serendipitous Okanagana spp. emergence as a biotic source influencing lazuli bunting behavior. Both species produce songs that share substantial spectral overlap with low-frequency, water-generated noise, and lazuli bunting song shares an additional high-frequency overlap with cicada calls. Thus, there is potential for background acoustic conditions to mask conspecific signals. We found that detection and discrimination of conspecific playback occurred more slowly for both species as sound level increased. Lazuli buntings also exhibited divergent flight behaviors in response to high- and low-frequency acoustic sources, both dependent and independent of sound level. In Chapter 2, we investigated how amplitude and frequency of water-generated noise influences spectral and temporal song characteristics in six songbird species. We recorded individuals defending territories across 37 sites, with each site representing one of four acoustic environments: naturally quiet ‘controls’, naturally noisy ‘positive controls’ adjacent to the ocean or a whitewater river, ‘phantom’ playback sites with continuous broadcast of low-frequency water noise, and ‘shifted’ playback sites with continuous broadcast of high-frequency water noise. We predicted that all individuals exposed to ‘positive control’, ‘phantom’, or ‘shifted’ noise would adjust song structure, but the magnitude of signal modification would be larger in noisier locations and the type of modification would depend on the spectral profile of the acoustic environment. No two species altered songs in precisely the same way. However, song structure of all six species varied with amplitude and/or frequency of background noise. Together our results demonstrate that natural noise can impair agonistic behaviors and influence vocal structure. These findings suggest that the natural acoustic environment shapes acoustic communication, highlighting natural soundscapes as an under-appreciated axis of the environment.

L'objet de cette thèse est l'étude des possibles mécanismes élastiques expliquant l'amplification du bruit ambiant au droit de certains réservoirs multi-phasiques. Trois jeux de données sont traités. La signature spectrale observée d'un réservoir de vapeur géothermique est différente de celle d'un stockage de gaz. Dans une approche empirique, un algorithme de classification permet d'extraire et de cartographier les anomalies que l'on présume liées au réservoir. Un travail de modélisation est effectué pour tenter d'expliquer les anomalies mesurées. Dans les données réelles, une forte présence de modes supérieurs d'ondes de Rayleigh est détectée. On modélise numériquement en 2D la propagation de ces modes à travers un réservoir placé au sein d'une structure géologique réaliste. La réponse simulée du réservoir se révèle trop faible par rapport aux observations de terrain. Néanmoins, on parvient à inverser les faibles perturbations d'amplitude synthétiques pour la position du réservoir, dans des modèles de référence simples. Cette méthode pourrait être utilisable pour l'imagerie à partir de faibles variations d'amplitudes dans le cadre du monitoring. Pour ce qui est de fortes anomalies observées sur le terrain , il est à noter que les effets visco-élastiques, les effets 3D, et les effets liés à un éventuel champ incident diffus n'ont pas été pris en compte dans la modélisation. Ainsi ce travail n'exclut pas la possibilité de telles anomalies liées à la présence d'un réservoir. / This PhD work investigates the possible elastic mechanisms behind the ambient noise amplification above multi-phase fluid reservoirs. Three datasets are analysed above different reservoirs. The observed spectral signature is different in the gas storage and geothermal contexts. A non-supervised algorithm for amplitude spectrum classification is developed, allowing to extract and map the relevant attributes of a multi-phase fluid presence. As a first modelling step, a wavefield characterisation methodology is applied to determine the composition of the ambient noise. It reveals the presence of strong Rayleigh overtones. Numerical 2D elastic modelling is used to simulate the propagation of overtones across a reservoir within a realistic geological structure. The modelled reservoir response is too small compared to the real data. However, the small amplitude perturbations arising in the numerical simulations are successfully inverted for the position of the reservoir, in simple background models. The developed method could in theory be used for imaging small time-lapse amplitude variations (monitoring), despite the obstacles remaining to be overcome before a real-data application. Neither visco-elastic nor 3D effects are adressed. Thus this work does not exclude the possibility of strong reservoir-specific spectral anomalies.

Les effets de site peuvent augmenter fortement la durée et l’amplitude des sollicitations sismiques imposées aux structures. Les effets de site 2D-3D induisent des amplifications sur une large bande de fréquence qui ne peuvent pas être simulées numériquement jusqu’à haute fréquence (>2-4 Hz) du fait de la limite de résolution des connaissances géologiques, géophysiques et/ou géotechniques du sous-sol. Les évaluations empiriques des effets de site sont donc indispensables pour pouvoir observer ce phénomène complexe de façon fiable jusqu’à haute fréquence. De telles évaluations nécessitent l'enregistrement de bonne qualité de nombreux séismes ce qui rend leur obtention rapide difficile dans les régions faiblement actives.Ce travail présente une analyse comparative de ces évaluations empiriques sur deux sites très différents, l’un en contexte sismique modéré (Provence, France) et l’autre en contexte très actif (Céphalonie, Grèce). Sur le site provençal, 500 séismes ont pu être enregistrés en l’espace de 2½ ans grâce à l’utilisation de vélocimètres. Une mesure du paramètre d’atténuation de site k_0 a ainsi pu être réalisée via l’analyse des spectres en accélération (k_(0_AS)) et en déplacement (k_(0_DS)). La mesure de k_0 n’est relativement fiable que sur les sites au rocher du fait des amplifications de site au sédiment. La méthode des rapports spectraux sismique (SSR) permet l’évaluation des effets de site relatif à partir des nombreux enregistrements de mouvement faible. Les résultats montrent une forte variabilité épistémique attribuable à l’éclairage induit par la position de la source sismique vis-à-vis du bassin. Ainsi, une estimation fiable de la réponse des sites est possible à partir de quelques évènements seulement dans le cas 1D, mais nécessite un nombre beaucoup plus important de séismes répartis de façon homogène autour du site dans les cas 2D-3D. Les résultats SSR moyens sont ensuite comparés à ceux issus des méthodes utilisant le bruit ambiant. Conformément aux attentes, la méthode des rapports spectraux H/V (HVSR) ne permet que de caractériser la fréquence fondamentale pour certains sites. À l’inverse, la méthode SSR appliquée au bruit ambiant (SSRn) montre des résultats très comparables à ceux de la méthode SSR jusqu’à haute fréquence à la condition que le site de référence soit pris dans le bassin sédimentaire. Les approches par corrélation de bruit (cohérence et ANIRF) révèlent qu’une estimation de la fonction de transfert relative à un site de référence au rocher est possible au moins jusqu’à basse fréquence (<4 Hz). L’utilisation du bruit ambiant permet ainsi d’envisager l’évaluation rapide de la réponse des sites et de sa variabilité spatiale (microzonage), même lorsque la sismicité est faible. Partout, les méthodes empiriques d’évaluation des effets de site apportent un complément essentiel aux approches numériques qui reste indispensables.Ces résultats permettent de proposer une méthodologie d’évaluation de l’aléa sismique site-spécifique qui se décompose en trois étapes principales : (i) ajustement des équations de prédictions de mouvement du sol (GMPEs) sur le site de référence au rocher au moyen, entre autres, de k_(0_DS) ; (ii) évaluation empirique fiable de la réponse d’au moins un site dans le bassin relativement au site de référence (pour lequel les GMPEs ont été ajustées) par la méthode SSR; (iii) réalisation de cette évaluation à partir de l’ANIRF dans les régions les moins actives sismiquement et/ou extension à toute la zone d’étude à partir du SSRn. Cette méthodologie permet d’envisager une bien meilleure prise en compte des effets de site (en particulier 2D-3D) et une réduction importante des incertitudes dans les évaluations de l’aléa sismique spécifique à un site. Elle nécessite simplement l’enregistrement simultané de séismes sur au moins deux sites équipé de vélocimètres sensibles, et la réalisation de campagnes de mesure temporaire du bruit ambiant, si nécessaire. / Site effects can greatly increase both the duration and the amplitude of the seismic solicitation imposed on structures. 2D-3D site effects induce broadband amplifications that cannot be simulated up to high frequency (>2-4 Hz) due to the limited resolution of the geological, geophysical and/or geotechnical information. Empirical site effect assessment is therefore essential for reliable observations of this complex phenomenon up to high frequency. However, such assessments often require good quality records from many earthquakes that cannot be rapidly obtained in low seismicity areas.This work presents a comparative analysis of these empirical evaluations on two very different sites, the first in a moderate seismicity context (Provence, France) and the second in a very active context (Kefalonia, Greece). For the Provençal site, nearly 500 earthquakes were recorded in only 2½ years thanks to the use of velocimeters. The site attenuation parameter κ_0 could thus be measured both on the acceleration (κ_(0_AS)) and displacement (κ_(0_DS)) spectra. Our results show that the measurement of κ_0 is relatively reliable on rock sites only, mainly due to the too great disturbance by the amplification for sedimentary sites, even for those that are quite stiff. The standard spectral ratio (SSR) approach provides the relative site effects from the numerous weak motion recordings available at sites located in Provence and Kefalonia. The results show a strong epistemic variability due to the lighting induced by the position of the seismic source with respect to the basin. Thus, while a reliable site response estimation is possible from only a few events for 1D geometries, it requires much more earthquakes evenly distributed around the site when the geometry is 2D-3D. The mean SSR results are then compared with those obtained from methods using the ambient noise. As expected, the H/V spectral ratio approach (HVSR) provides only the fundamental frequency for some sites. Conversely, SSR applied to ambient noise (SSRn) shows very similar results to the SSR method up to high frequency, provided that the reference site is taken in the sedimentary basin. Approaches using the noise correlation (coherence and ANIRF) reveal that the transfer function relative to a rock reference site can be estimated at least up to low frequency (<4 Hz). Methods using ambient noise are promising for a rapid evaluation of the site response and its spatial variability (microzoning), even when seismicity is low. Empirical site effects methods are therefore applicable everywhere. They provide an essential complement to numerical approaches, which remain inevitable when the coverage of available earthquakes is not homogeneous or when soils are likely to present non-linear behaviors.These results led us to propose a methodology for the evaluation of the site-specific seismic hazard, which consists of three main stages: (i) adjustment to the rock reference site of the ground motion prediction equations (GMPEs) using, among others, κ_(0_DS); (ii) Reliable evaluation of the SSR transfer function between at least one site in the basin and the reference site (for which the GMPEs were adjusted); (iii) carrying out this assessment from the ANIRF in the less seismically active regions and/or extension to the entire study area with the SSRn. This methodology allows a much better consideration of the site effects (especially 2D-3D) and a significant reduction of the uncertainties in the evaluations of the site-specific seismic hazard. It only required, simultaneous recording of earthquakes on at least two sites equipped with sensible velocimeters, and to carrying out temporary campaign of ambient noise measurements, if necessary.

Three-fifths of the Earth’s crust has been built at oceanic spreading centres in the last 160 million years. To explore crustal extension processes and the architecture of these constructive plate boundaries I have studied the oceanic rift in Iceland. Here the Mid Atlantic Ridge is anomalously elevated above sea level and thus easier to instrument. I have deployed and operated a dense network of seismometers in the remote volcanic highlands in central Iceland, and used the passive seismic data collected from this network to explore crustal structure and volcanic processes in the extensional rift zones. My analysis of persistent seismicity located in an intervening region between individual spreading segments, uniquely records the segmentation of plate spreading on the scale of individual volcanic systems. Precise location and characterisation of micro-earthquakes identifies a series of faults subparallel to the rift fabric, and source mechanisms define left-lateral strike-slip motion on these faults. This extremely high quality microseismic data reveals transform motion being accommodated by bookshelf faulting in a concentrated region between two such volcanic systems, providing evidence for the localisation of spreading in the discrete volcanic systems. While transform motion between spreading centres appears to be accommodated on a continuous basis, the extension of the brittle upper crust within the spreading centres occurs episodically during rifting events. Our local seismic network fortuitously recorded such a rifting episode in August 2014, during which the opening of a 5 metre wide dyke triggered a huge increase in seismicity across large areas of the rift zone. Stress-seismicity-rate modelling of this triggered seismicity, along with geodetic constraints on the deformation, provided a remarkable opportunity with which it was possible to prove the existence of stress-shadowing, a challenge which has eluded earthquake seismologists for decades. Using the excellent coverage of our extended seismic network I have also generated a new high resolution image of the regional crustal seismic structure using surface waves extracted from ambient seismic noise. The structure reveals low seismic velocities which are closely correlated with the volcanic rift zones, and faster wavespeeds in the older and non-volcanically active Tertiary crust. The strongest anomalies are seen in the north-west of the Vatnajökull icecap, at the location of thickest crust and inferred centre of the underlying mantle plume. Inversion for shear wave velocity structure shows high velocity-gradients in the top 10 km, defining a thickened extrusive upper crust in Iceland compared to standard oceanic crust, where it is normally 2–3 km thick. Below this, the shear wave velocity structure reveals a distinct low-velocity zone in the mid crust between 14–20 km depth, which is widespread across Iceland and shallows into the active volcanic rifts. This extensive feature suggests high mid-crustal temperatures and a high temperature-gradient between the extrusives of the upper crust and the intrusive mid-to-lower crust in Iceland.

Les processus volcaniques et tectoniques sont à l'origine de la création de la croûte océanique et de la sismicité des dorsales, mais sont rarement détectés par les stations sismologiques. Les réseaux d'hydrophones, immergés dans la colonne d'eau océanique, sont capables d'enregistrer les phases acoustiques produites par les séismes sous-marins, les ondes T. Dans l'océan Indien, il y a trois dorsales à taux d'expansion contrastés, les dorsales Sud-Ouest Indienne, Centrale Indienne et Sud-Est Indienne; c'est donc le lieu idéal pour examiner les relations entre sismicité et taux d'expansion. À cet effet, le réseau OHASISBIO, a permis la détection de plus de 1400 séismes en un an le long de ces trois dorsales, soit cinq fois plus que les stations sismologiques.Nonobstant leur taux d'expansion contrastés, le taux de sismicité moyen des dorsales est similaire, montrant qu'il n'y a pas de relation directe entre taux d'expansion et de sismicité. La distribution des séismes le long de l'axe de chaque dorsale est contrastée et révèle des modes d'accrétion différents. Le long de la dorsale Sud-Ouest Indienne, la sismicité est peu abondante mais régulièrement distribuée le long de l'axe à l'est de la zone de fracture de Melville. Au contraire, le long des dorsales Sud-est et Centrale indiennes, la sismicité est bien corrélée avec la segmentation. Les séismes sont concentrés aux extrémités des segments et autour des discontinuités; les centres de segments sont majoritairement asismiques à l'exception des sites hydrothermaux de la dorsale Centrale Indienne et d'un segment actif de la dorsale Sud-Est Indienne. Les variations de la sismicité à l'échelle du segment reflètent l'état thermique de la croûte sous les dorsales Centrale et Sud-Est Indienne cependant que les variations à grande échelle expriment des phénomènes plus profonds sous la dorsale Sud-Ouest Indienne. / Volcanic and tectonic events are responsible for the seismicity associated with sea floor spreading. They are yet poorly detected by land-based seismological networks. Arrays of hydrophones, moored into the SOFAR channel, are capable of recording the seismo-acoustic phase generated by low-magnitude submarine earthquakes, the T waves. In the Indian Ocean, there are three mid-oceanic ridges with contrasted spreading rates, the Southwest, Central and Southeast indian ridges; it is thus the ideal place for examining the relationships between seismicity and spreading rate. To this effect, the OHASISBIO network of hydrophones, detected more than 1400 earthquakes in a year along the three mid-oceanic ridges in the Indian Ocean, which is about five times more events than land-based networks.Although the ridges have contrasted spreading rates, their mean seismicity rates are similar, suggesting that there is no direct relationship between seismicity and spreading rates. The along axis distribution of the seismicity, however, is contrasted and reveals fundamentally different modes of accretion. Along the Southwest Indian Ridge, events are sparse but regularly distributed along the axis, especially east of the Melville fracture zone and in good agreement with tectonic extension. On the contrary, along the Central and Southeast indian ridges, the seismicity is well correlated with the segmentation. Earthquakes cluster at segment ends and discontinuities whereas segment centres are mostly aseismic, except at hydrothermal sites on the Central Indian Ridge and one active segment on the Southeast Indian Ridge. Overall, segment-scale variations in the seismicity reflect the thermal state of the crust beneath the Central and Southeast Indian ridges whereas larger scale variations reveal changes in the mantle temperature under the Southwest Indian Ridge.

It is estimated that 10% of the global population is impaired to a significant degree by a decrease in hearing sensitivity. With the greatest proportion of these persons residing in developing countries where communities are grossly underserved, it is incumbent on hearing healthcare professionals to seek means of offering equitable hearing health care services to these communities. The delivery of conventional diagnostic hearing services to these population groups is challenged by limitations in human resources, financial constraints and by the dearth of audiometric testing facilities that are compliant with permissible ambient noise levels for reliable testing. Valid diagnostic hearing assessment without an audiometric test booth will allow greater mobility of services and could extend hearing healthcare service delivery in underserved areas. The purpose of this study was to investigate the validity of diagnostic pure tone audiometry in a natural environment, outside a sound treated room, using a computer-operated audiometer with insert earphones covered by circumaural earcups incorporating real-time monitoring of environmental noise. A within-subject repeated measures research design was employed to assess elderly adults with diagnostic air (250 to 8000 Hz) and bone (250 to 4000 Hz) conduction pure tone audiometry. The study was of a quantitative nature and the required data was collected by testing subjects initially in a natural environment and subsequently in a sound booth environment to compare the threshold measurements. One experienced audiologist used audiometric KUDUwave test equipment to evaluate subjects in both environments. A total of 147 adults with an average age of 76 (± 5.7) years were tested. Ears had pure tone averages (500, 1000, 2000 and 4000 Hz) of ≥ 25 dB in 59%, >40 dB in 23% and ˃ 55 dB in 6% of cases. Analysis of collected data showed air conduction thresholds (n = 2259) corresponding within 0 to 5 dB in 95% of all comparisons between testing in the natural and sound booth environments. Bone conduction thresholds (n = 1669) corresponded within 0 to 5 dB in 86% of comparisons and within 10 dB or less in 97% of cases. Average threshold differences (–0.6 to 1.1) and standard deviations (3.3 to 5.9) were within typical test-retest reliability limits. Recorded thresholds showed no statistically significant differences with a paired samples t-test (p ˃ 0.01) except at 8000 Hz in the left ear. Overall the correlation between the air-conduction thresholds recorded in the sound booth environment and the natural environment was very high (˃ 0.92) across all frequencies while for bone conduction threshold correlation for the two environments fell between 0.63 and 0.97. This study demonstrates that valid diagnostic pure tone audiometry in an elderly population can be performed in a natural environment using an audiometer employing insert earphones covered by circumaural earcups with real-time monitoring of ambient noise levels. Mobile diagnostic audiometry performed outside of an audiometric sound booth may extend current hearing healthcare services to remote underserved communities where booths are scarce or inaccessible. In combination with Telehealth applications this technology could offer a powerful and viable alternate diagnostic service to persons unable to attend conventional testing facilities for whatever reasons. / Dissertation (MCommunication Pathology)--University of Pretoria, 2013. / gm2014 / Speech-Language Pathology and Audiology / Unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21950号 / 理博第4528号 / 新制||理||1650(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 釜井 俊孝, 教授 千木良 雅弘 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

In this study, ambient noise wavefield was used for the first time to image spatial and temporal upper crustal seismic structures in NW-Bohemia/Vogtland region. The data come from 111 stations and were collected from continuous recordings of the permanent station networks of Germany and Czech Academy of Sciences as well as temporary stations of the BOHEMA and PASSEQ experiments. Rayleigh and Love waves travelling between each station-pair are extracted by cross-correlating long time series of ambient noise data recorded at the stations. Group velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions between 0.1 and 1 Hz, and are tomographically inverted to provide 2-D group velocity maps. At shorter periods Rayleigh wave group velocity maps are in good agreement with surface geology where low velocity anomalies appear along Mariánské Lázně Fault and Eger rift. A low velocity zone is observed at the northern edge of Mariánské Lázně Fault which shifts slightly to the south with increasing period and correlates well with the main focal zone of the earthquake swarms at 5 s period. We invert the 2-D group velocity maps into a 3-D shear wave velocity model. In this step Love waves were excluded from further analysis because of their high level of misfit to modelled dispersion curves. Horizontal and vertical sections through the model reveal a clear low velocity zone above the Nový Kostel seismic focal zone which narrows towards the top of the seismic activity and ends above the shallowest hypocenters at 7 km depth. We investigate temporal variation of seismic velocity within and around the Nový Kostel associated with 2008 and 2011 earthquake swarms by employing Passive Image Interferometry method using 7 continuous seismograms recorded by the WEBNET network. The results reveals stable seismic velocities without a clear post seismic velocity change during earthquake swarms in the Nový Kostel area.

Ce travail vise à améliorer la compréhension des signaux sismiques dérivés des fonctions de corrélation inter-récepteur du bruit sismique, ce qui est critique pour une imagerie fiable de la Terre profonde basée sur le bruit. La thèse comprend sept chapitres. Le chapitre 1 introduit les connaissances de base sur le bruit sismique, de la terminologie à ses origines diverses. Le chapitre 2 fournit une vue d'ensemble de la littérature sur l'historique et le développement de la méthode récente de corrélation de bruit, et passe en revue diverses techniques pour le prétraitement des données de bruit sismique et le post-traitement des fonctions de corrélation de bruit. Des méthodes de traitement du bruit basées sur les statistiques et un schéma modifié pour calculer la fonction de corrélation sont développés dans ce chapitre. Le chapitre 3 propose plusieurs techniques basées sur la transformée de Radon pour mesurer les lenteurs des champs d'ondes corrélés et analyser en termes de phases sismiques les signaux dérivés du bruit. Le chapitre 4 montre que les ondes de volume sondant la Terre profonde peuvent être extraites des corrélations de bruit à des distances télésismiques, avec des enregistrements de bruit provenant de deux réseaux sismiques régionaux. Le chapitre 5 applique les techniques proposées au chapitre 3 aux corrélations de bruit entre deux réseaux calculées au chapitre 4, et permet de comprendre l’origine de la phase précoce non-physique observée dans les données. Le chapitre 6 discute des conditions dans lesquelles apparaissent des phases sans correspondance dans la réponse physique de la Terre qui peuvent fausser les analyses des structures profondes basées sur le bruit.. Le dernier chapitre fournit un résumé sur les contributions de cette thèse et une perspective de plusieurs travaux soit en cours soit envisagés pour le futur. / This work aims toward an improved understanding of the seismic signals derived from the inter-receiver correlation functions of seismic noise, which is valuable and critical for a reliable noise-based deep Earth imaging. The thesis consists of seven chapters. Chapter 1 introduces background knowledge on seismic noise, from its classifications to various origins. Chapter 2 provides a literature overview on the history and development of the emerging noise correlation method, and reviews various techniques for the pre-processing of seismic noise data and post-processing of noise correlation functions. Statistics-based noise processing methods and a modified scheme for computing correlation function are developed in this chapter. Chapter 3 proposes several Radon-based techniques to analyze the slownesses of correlated wavefields and to unveil the origin of noise-derived seismic signals. Chapter 4 shows that body waves penetrating into deep Earth can be extracted from noise correlations at teleseismic distances, with noise records from two regional seismic networks. Chapter 5 applies the techniques proposed in chapter 3 to the double-array nose correlations computed in chapter 4, and accordingly reveals the origin of an early spurious phase observed in chapter 4. Chapter 6 discusses several situations that bring ambiguities into the noise-derived seismic signals and can potentially bias the noise-based imaging of subsurface structure. The last chapter provides a summarization over the contributions of this thesis and an outlook of several ongoing and prospected works.