There currently exists no reliable, non-destructive method for measuring stress in railroads and other similar structures without the need for a calibration measurement. Major limitations which have hindered previous techniques include sensitivity to boundary conditions, insensitivity to stress, and intolerance for material and geometry uncertainty. In this work, a technique is developed which seeks to solve these challenges by extracting the spectrum relation, or dispersion curve, of a waveguide from dispersive wave propagation meaasurements. The technique is based on spectral analysis of waves in structures modeled as beams, and as such is based on relatively low frequency vibrations, as opposed to other techniques which use nonlinear elastic modeling of structures at ultrasonic frequencies. The major contribution of this work is the development of a frequency-domain based signal processing technique which is capable of compensating for the dispersive, long wavelength reflections which have limited the ability of previous techniques to go low enough in frequency to achieve high stress sensitivity. By compensating for reflections, the present work is able to automate the process of analyzing wave propagation signals such that the entire dispersion curve can be extracted, enabling the identification of various parameters including stress, stiffness, density, and other material and geometry properties. This in turn enables measuring stress, performing model-updating for material and geometry uncertainty, and being indifferent to boundary conditions. The theory and algorithmic implementation is presented, along with simulations and experimental validation on a rectangular beam. / Master of Science / The ability to detect damage or the potential for damage in structures is highly desirable, especially in industries such as civil infrastructure in which failure can be incredibly costly and dangerous. In particular, non-destructive techniques which can predict failure without interfering with the operations of a structure are particularly sought after. In this work, a technique for non-intrusively and non-destructively measuring stress is developed, with the primary application being for measuring stress in railroads. The technique seeks to advance the state-of-the-art in wave-propagation-based techniques by adding the capability to automatically identify reflected waves. With this new capability, the method is able to quickly and efficiently analyze a large set of vibration measurements to extract information about the structure's material, geometry, and loading characteristics which enables solving for stress even when the structures material, geometry, and boundary conditions are not precisely known. The technique is demonstrated on both simulated and experimental data, in which a rectangular beam is tensioned and the stress is then identified.

La problématique récente de la conception de métamatériaux a renouvelé l'intérêt dans les théories de l'homogénéisation en régime dynamique. En particulier, la théorie de l'homogénéisation élastodynamique initiée par J.R. Willis a reçu une attention particulière suite à des travaux sur l'invisibilité élastique. La présente thèse reformule la théorie de Willis dans le cas des milieux périodiques, examine ses implications et évalue sa pertinence physique au sens de quelques ``conditions d'homogénéisabilité'' qui sont suggérées. En se basant sur les résultats de cette première partie, des développements asymptotiques approximatifs de la théorie de Willis sont explorés en relation avec les théories à gradient. Une condition nécessaire de convergence montre alors que toutes les branches optiques de la courbe de dispersion sont omises quand des développements asymptotiques de Taylor de basse fréquence et de longue longueur d'onde sont déployés. Enfin, une nouvelle théorie de l'homogénéisation est proposée. On montre qu'elle généralise la théorie de Willis et qu'elle l'améliore en moyenne fréquence de sorte qu'on retrouve certaines branches optiques omises auparavant. On montre également que le milieu homogène effectif défini par la nouvelle théorie est un milieu généralisé dont les champs satisfont une version élastodynamique généralisée du lemme de Hill-Mandel / The recent issue of metamaterials design has renewed the interest in homogenization theories under dynamic loadings. In particular, the elastodynamic homogenization theory initiated by J.R. Willis has gained special attention while studying elastic cloaking. The present thesis reformulates Willis theory for periodic media, investigates its outcome and assesses its physical suitability in the sense of a few suggested ``homogenizability conditions''. Based on the results of this first part, approximate asymptotic expansions of Willis theory are explored in connection with strain-gradient media. A necessary convergence condition then shows that all optical dispersion branches are lost when long-wavelength low-frequency Taylor asymptotic expansions are carried out. Finally, a new homogenization theory is proposed to generalize Willis theory and improve it at finite frequencies in such a way that selected optical branches, formerly lost, are recovered. It is also proven that the outcome of the new theory is an effective homogeneous generalized continuum satisfying a generalized elastodynamic version of Hill-Mandel lemma

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23861号 / 工博第4948号 / 新制||工||1773(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 清野 純史, 教授 三村 衛, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs has been used to construct models of FZ structure. However, the depth extent of the waveguide and the uniqueness of deep structure in the models have been debated. Elastic finite-difference synthetic seismograms were generated for FZ models that include an increase in seismic velocity with depth both inside and outside the FZ. Strong GWs were created from sources both in and out of the waveguide, in contrast with previous homogenous-FZ studies that required an in-fault source to create GW. This is because the frequency-dependent trapping efficiency of the waveguide changes with depth. The near-surface fault structure efficiently guides waves at lower frequencies than the deeper fault. Fault structure at seismogenic depth requires the analysis of data at higher frequencies than the GWs that dominate at the surface. Adapting a two-station technique from surface wave studies, dispersive differential group arrival times between two earthquakes can be used to solve for FZ structures between the earthquakes. This method was tested with synthetic data and shallow events recorded in the SAFOD borehole in the San Andreas Fault. A pair of deep earthquakes recorded in the SAFOD borehole indicate a ~150 m wide San Andreas Fault waveguide with >20% velocity contrast at 10-12 km depth. With additional earthquakes, the full FZ structure at seismogenic depth could be imaged. Subsurface FZ structure can also be derived from a surface source and receiver array analogous to a body-wave refraction survey. Synthetic seismograms for such source-receiver geometry were generated and verified that FZGWs are refracted by the increase in velocity with depth. Synthetic data from a surface array were successfully inverted to derive FZ structure in the subsurface. The new methods presented in this dissertation extend the potential of FZGWs to image deeper FZ structure than has been uniquely constrained in the past. / Ph. D.

Os métodos de ondas superficiais com ênfase nas ondas Rayleigh foram utilizados como o núcleo desse trabalho de Doutorado. Inicialmente, as ondas Rayleigh foram modeladas permitindo o estudo de sensibilidade de suas curvas de dispersão sob diferentes configurações de parâmetros físicos representando diversos modelos de camadas, em que pôde ser observado parâmetros com maior e menor sensibilidade e também alguns efeitos provocados por baixas razões de Poisson. Além disso, na fase de inversão dos dados a modelagem das ondas Rayleigh foi utilizada para a construção da função objeto, que agregada ao método de mínimos quadrados, a partir do método de Levenberg-Marquardt, permitiu a implementação de um algoritmo de busca local responsável pela inversão de dados das ondas superficiais. Por se tratar de um procedimento de busca local, o algoritmo de inversão foi complementado por uma etapa de pré-inversão com a geração de um modelo inicial para que o procedimento de inversão fosse mais rápido e eficiente. Visando uma eficiência ainda maior do procedimento de inversão, principalmente em modelos de camadas com inversão de velocidades, foi implementado um algoritmo de pós-inversão baseado em um procedimento de tentativa e erro minimizando os valores relativos da raiz quadrada do erro quadrático médio (REQMr) da inversão dos dados. Mais de 50 modelos de camadas foram utilizados para testar a modelagem, a pré-inversão, inversão e pós-inversão dos dados permitindo o ajuste preciso de parâmetros matemáticos e físicos presentes nos diversos scripts implementados em Matlab. Antes de inverter os dados adquiridos em campo, os mesmos precisaram ser tratados na etapa de processamento de dados, cujo objetivo principal é a extração da curva de dispersão originada devido às ondas superficiais. Para isso, foram implementadas, também em Matlab, três metodologias de processamento com abordagens matemáticas distintas. Essas metodologias foram testadas e avaliadas com dados sintéticos e reais em que foi possível constatar as virtudes e deficiências de cada metodologia estudada, bem como as limitações provocadas pela discretização dos dados de campo. Por último, as etapas de processamento, pré-inversão, inversão e pós-inversão dos dados foram unificadas para formar um programa de tratamento de dados de ondas superficiais (Rayleigh). Ele foi utilizado em dados reais originados pelo estudo de um problema geológico na Bacia de Taubaté em que foi possível mapear os contatos geológicos ao longo dos pontos de aquisição sísmica e compará-los a um modelo inicial existente baseado em observações geomorfológicas da área de estudos, mapa geológico da região e informações geológicas globais e locais dos movimentos tectônicos na região. As informações geofísicas associadas às geológicas permitiram a geração de um perfil analítico da região de estudos com duas interpretações geológicas confirmando a suspeita de neotectônica na região em que os contatos geológicos entre os depósitos Terciários e Quaternários foram identificados e se encaixaram no modelo inicial de hemi-graben com mergulho para Sudeste. / The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical information associated with geological information allowed the generation of an analytical profile of the study region with two geological interpretation confirming the suspect of neotectonic movements in the region wherein the geological contacts between the quaternary and tertiary deposits were identified and they agreed with the initial model of a hemi-graben with dip to Southeast.

A recent shallow earthquake in the Corinth Gulf, Greece (Mw 5.3) generated unusual long-period waves (periods > 5 seconds) between the P- and S-wave arrival. The 5-second period, being significantly longer than the source duration, indicates a structural effect. Observed seismograms were examined by methods of the frequency-time analysis. Disper- sion curves of the fast long-period (FLP) waves indicated group velocities ranging from 3 to 5.5 km/s for periods between 4 and 10 s, respectively, with large variations among the stations. The generalized dispersion curve splits into two major strips, probably related to lateral variations of the crustal structure. Forward simulations for several existing crustal models were made. A few partially successful models served for a sensitivity study, which showed that the FLP wave seemed to be mainly due to the low-velocity layers in the uppermost 4 kilometers of the crust. Finally the shallow crustal structure was retrieved by inverting observed seismograms by Neighborhood algorithm. The inversion confirmed that the FLP wave in seismograms at more than a single station cannot be explained with a 1-D crustal model. The path-dependent models provided a partial explanation for the strips revealed in the experimental dispersion curves. An alternative explanation is by...

Os métodos de ondas superficiais com ênfase nas ondas Rayleigh foram utilizados como o núcleo desse trabalho de Doutorado. Inicialmente, as ondas Rayleigh foram modeladas permitindo o estudo de sensibilidade de suas curvas de dispersão sob diferentes configurações de parâmetros físicos representando diversos modelos de camadas, em que pôde ser observado parâmetros com maior e menor sensibilidade e também alguns efeitos provocados por baixas razões de Poisson. Além disso, na fase de inversão dos dados a modelagem das ondas Rayleigh foi utilizada para a construção da função objeto, que agregada ao método de mínimos quadrados, a partir do método de Levenberg-Marquardt, permitiu a implementação de um algoritmo de busca local responsável pela inversão de dados das ondas superficiais. Por se tratar de um procedimento de busca local, o algoritmo de inversão foi complementado por uma etapa de pré-inversão com a geração de um modelo inicial para que o procedimento de inversão fosse mais rápido e eficiente. Visando uma eficiência ainda maior do procedimento de inversão, principalmente em modelos de camadas com inversão de velocidades, foi implementado um algoritmo de pós-inversão baseado em um procedimento de tentativa e erro minimizando os valores relativos da raiz quadrada do erro quadrático médio (REQMr) da inversão dos dados. Mais de 50 modelos de camadas foram utilizados para testar a modelagem, a pré-inversão, inversão e pós-inversão dos dados permitindo o ajuste preciso de parâmetros matemáticos e físicos presentes nos diversos scripts implementados em Matlab. Antes de inverter os dados adquiridos em campo, os mesmos precisaram ser tratados na etapa de processamento de dados, cujo objetivo principal é a extração da curva de dispersão originada devido às ondas superficiais. Para isso, foram implementadas, também em Matlab, três metodologias de processamento com abordagens matemáticas distintas. Essas metodologias foram testadas e avaliadas com dados sintéticos e reais em que foi possível constatar as virtudes e deficiências de cada metodologia estudada, bem como as limitações provocadas pela discretização dos dados de campo. Por último, as etapas de processamento, pré-inversão, inversão e pós-inversão dos dados foram unificadas para formar um programa de tratamento de dados de ondas superficiais (Rayleigh). Ele foi utilizado em dados reais originados pelo estudo de um problema geológico na Bacia de Taubaté em que foi possível mapear os contatos geológicos ao longo dos pontos de aquisição sísmica e compará-los a um modelo inicial existente baseado em observações geomorfológicas da área de estudos, mapa geológico da região e informações geológicas globais e locais dos movimentos tectônicos na região. As informações geofísicas associadas às geológicas permitiram a geração de um perfil analítico da região de estudos com duas interpretações geológicas confirmando a suspeita de neotectônica na região em que os contatos geológicos entre os depósitos Terciários e Quaternários foram identificados e se encaixaram no modelo inicial de hemi-graben com mergulho para Sudeste. / The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical information associated with geological information allowed the generation of an analytical profile of the study region with two geological interpretation confirming the suspect of neotectonic movements in the region wherein the geological contacts between the quaternary and tertiary deposits were identified and they agreed with the initial model of a hemi-graben with dip to Southeast.

A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final. / The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.

A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final. / The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.

Submitted Ph.D. thesis is concerning the application and interpretation of seismic surface waves in a broad range of frequencies and scales. Using surface waves as a supplement to the methods dealing with body waves seems to be worth the effort. Surface wave interpretation can be used to obtain new information about the studied medium and simultaneously it can overcome, in some cases, the limitations of other seismic techniques. Moreover, surface waves are usually present on measured records and hence for its usage it is not necessary to modify the standard measuring procedures. One of the results of this thesis is an original algorithm for dispersive waveform calculation. The program works in an arbitrary range of frequencies and scales. The input parameter for the calculation is the dispersion curve. In this point the algorithm differs from all other approaches used so far. Algorithm is based on a summation of frequency components with shifts corresponding to the velocity dispersion and distance. The resulting waveform only contains an individual dispersive wave of the selected mode, thus being particularly suitable for testing of methodologies for dispersive wave analysis. The algorithm was implemented into the program DISECA. Furthermore, a new procedure was designed to calculate the dispersion...