Previous work has shown that the strongest concentrations of lunar crustal magnetic anomalies are located antipodal to four large, similarly aged impact basins (Orientale, Serenitatis, Imbrium, and Crisium). Here, we report results of a correlation study between magnetic anomaly clusters and geology in areas antipodal to Imbrium, Orientale, and Crisium. Unusual geologic terranes, interpreted to be of seismic or ejecta origin associated with the antipodal basins, have been mapped antipodal to both Orientale and Imbrium. All three antipode regions have many high-albedo swirl markings. Results indicate that both of the unusual antipode terranes and Mare Ingenii (antipodal to Imbrium) show a correlation with high-magnitude crustal magnetic anomalies. A statistical correlation between all geologic units and regions of medium to high magnetization when high-albedo features are present (antipodal to Orientale) may suggest a deep, possibly seismic origin to the anomalies. However, previous studies have provided strong evidence that basin ejecta units are the most likely sources of lunar crustal anomalies, and there is currently insufficient evidence to differentiate between an ejecta or seismic origin for the antipodal anomalies. Results indicate a strong correlation between the high-albedo markings and regions of high magnetization for the Imbrium, Orientale, and Crisium antipodes. Combined with growing evidence for an Imbrian age to the magnetic anomalies, this supports a solar wind deflection origin for the lunar swirls.

Este trabalho apresenta um procedimento de inversão magnética de três etapas no qual quantidades invariantes em relação à fonte magnética são sequencialmente invertidas para recuperar i) a geometria da fonte no substrato, ii) sua intensidade de magnetização e iii) a inclinação da magnetização da fonte. A primeira quantidade invertida (chamada função geométrica) é obtida pela razão entre a intensidade do gradiente da anomalia magnética e a intensidade do campo magnético anômalo. Para fontes homogêneas, a função geométrica depende apenas da geometria da fonte, o que permite a reconstrução da forma do corpo usando valores arbitrários para a magnetização. Na segunda etapa, a forma da fonte é fixa e a intensidade de magnetização é estimada ajustando o módulo do gradiente da anomalia magnética, uma quantidade invariante com a direção da magnetização e equivalente à amplitude do sinal analítico. Na última etapa, a forma da fonte e a intensidade da magnetização são fixas e a inclinação da magnetização é determinada ajustando a anomalia magnética. Além de recuperar a forma e a magnetização de fontes homogêneas, esta técnica permite, em alguns casos, verificar se as fontes magnéticas são homogêneas. Isto é possível pois a função geométrica de fontes heterogêneas pode ser ajustada por um modelo homogêneo, mas o modelo assim obtido não permite o ajuste da amplitude do sinal analítico nem da anomalia magnética. Esse é um critério que parece efetivo no reconhecimento de fontes fortemente heterogêneas. O método de inversão por etapas é testado em experimentos numéricos de computador e utilizado para interpretar uma anomalia magnética gerada por rochas básicas intrusivas da Bacia do Paraná. / This work presents a three step magnetic inversion procedure in which invariant quantities related to source parameters are sequentially inverted to provide i) cross-section of two-dimensional sources; ii)intensity of source magnetization, and iii) inclination of source magnetization. The first inverted quantity (called geometrical function) is obtained by rationing intensity gradient of total field anomaly and intensity of vector anomalous field. For homogenous sources, geometrical function depends only on source geometry thus allowing shape reconstruction by using arbitrary values for source magnetization. In the second step, source shape is fixed and magnetization intensity is estimated by fitting intensity gradient of total field anomaly, an invariant quantity with magnetization direction and equivalent to amplitude of the analytical signal. In the last step, source shape and magnetization intensity are fixed and magnetization inclination is determined by fitting magnetic anomaly. Besides furnishing shape and magnetization of homogeneous two-dimensional sources, this technique allows to check in some cases if causative sources are homogeneous. It is possible because geometrical function from inhomogeneous sources can be fitted by a homogeneous model but a model thus obtained does not fit the amplitude of analytical signal nor magnetic anomaly itself. This is a criterion that seems efective in recognizing strongly inhomogeneous sources. The proposed technique is tested with numerical experiments, and used to model a magnetic anomaly from intrusive basic rocks of Paraná Basin, Brazil.

Este trabalho apresenta um procedimento de inversão magnética de três etapas no qual quantidades invariantes em relação à fonte magnética são sequencialmente invertidas para recuperar i) a geometria da fonte no substrato, ii) sua intensidade de magnetização e iii) a inclinação da magnetização da fonte. A primeira quantidade invertida (chamada função geométrica) é obtida pela razão entre a intensidade do gradiente da anomalia magnética e a intensidade do campo magnético anômalo. Para fontes homogêneas, a função geométrica depende apenas da geometria da fonte, o que permite a reconstrução da forma do corpo usando valores arbitrários para a magnetização. Na segunda etapa, a forma da fonte é fixa e a intensidade de magnetização é estimada ajustando o módulo do gradiente da anomalia magnética, uma quantidade invariante com a direção da magnetização e equivalente à amplitude do sinal analítico. Na última etapa, a forma da fonte e a intensidade da magnetização são fixas e a inclinação da magnetização é determinada ajustando a anomalia magnética. Além de recuperar a forma e a magnetização de fontes homogêneas, esta técnica permite, em alguns casos, verificar se as fontes magnéticas são homogêneas. Isto é possível pois a função geométrica de fontes heterogêneas pode ser ajustada por um modelo homogêneo, mas o modelo assim obtido não permite o ajuste da amplitude do sinal analítico nem da anomalia magnética. Esse é um critério que parece efetivo no reconhecimento de fontes fortemente heterogêneas. O método de inversão por etapas é testado em experimentos numéricos de computador e utilizado para interpretar uma anomalia magnética gerada por rochas básicas intrusivas da Bacia do Paraná. / This work presents a three step magnetic inversion procedure in which invariant quantities related to source parameters are sequentially inverted to provide i) cross-section of two-dimensional sources; ii)intensity of source magnetization, and iii) inclination of source magnetization. The first inverted quantity (called geometrical function) is obtained by rationing intensity gradient of total field anomaly and intensity of vector anomalous field. For homogenous sources, geometrical function depends only on source geometry thus allowing shape reconstruction by using arbitrary values for source magnetization. In the second step, source shape is fixed and magnetization intensity is estimated by fitting intensity gradient of total field anomaly, an invariant quantity with magnetization direction and equivalent to amplitude of the analytical signal. In the last step, source shape and magnetization intensity are fixed and magnetization inclination is determined by fitting magnetic anomaly. Besides furnishing shape and magnetization of homogeneous two-dimensional sources, this technique allows to check in some cases if causative sources are homogeneous. It is possible because geometrical function from inhomogeneous sources can be fitted by a homogeneous model but a model thus obtained does not fit the amplitude of analytical signal nor magnetic anomaly itself. This is a criterion that seems efective in recognizing strongly inhomogeneous sources. The proposed technique is tested with numerical experiments, and used to model a magnetic anomaly from intrusive basic rocks of Paraná Basin, Brazil.

Este trabalho tem por objetivo descrever a Anomalia Magnética do Atlântico Sul (SAMA) utilizando os modelos para o período histórico (1600–1890) e também os modelos para o último século (DGRF e IGRF). Como a SAMA apresenta características de baixa intensidade do campo total e coincide com a região de intenso fluxo de partículas cósmicas, muitos problemas com objetos que orbitam a Terra (por exemplo, satélites) são detectados nessa região. São descritos os efeitos provocados pela SAMA em fenômenos espaciais. Através da análise dos modelos na forma de mapas, foram extraídos os dados de mínima intensidade para o centro da SAMA e a posição destes pontos, possibilitando conhecer a trajetória e as taxas de deriva. Os modelos foram testados na interface manto-núcleo através da componente vertical, para encontrar correlação com anomalias em superfície. Os resultados mostraram deriva para Oeste constante e variações em latitude. Foi observado que as intensidades acompanham a diminuição de todo o campo, embora a SAMA apresente caráter predominantemente não-dipolar, evidenciada pela razão entre o campo não-dipolar e o campo total no Atlântico Sul. A comparação de intensidades da SAMA com as medidas de intensidade realizadas pelos observatórios mostrou que a influência da SAMA aparece na forma de sobreposição ou amplificação de fenômenos com menor comprimento de onda, como os impulsos de variação secular (jerks geomagnéticos). A continuação para baixo dos modelos se mostrou satisfatória quando comparada com o método de inversão estocástica. A comparação da SAMA com outras anomalias em superfície mostrou independência na trajetória, porém, quando comparadas com os lóbulos principais na interface manto-núcleo, indicam que estas anomalias possam estar interligadas. Os lóbulos do núcleo foram interpretados com base nos mecanismos de geração, sugerindo que a SAMA possa ser originada através de movimentos combinados entre duas colunas de convecção e regiões de fluxo reverso no núcleo externo. / The object of this dissertation is to describe the South Atlantic Magnetic Anomaly (SAMA) using geomagnetic models for the historical period from 1600 to 1890 and also the IGRF and DGRF models for the past century. Since the SAMA presents low intensities of the total geomagnetic field that correspond to a region of intense cosmic ray particle flux, many problems with objects that orbit along this region (eg. Satelites) have been detected. The SAMA effects on space vehicles are described. The field models led to the definition of the SAMA center as the locus of minimum total field intensity and how the anomaly drifted and varied in intensity for the past four centuries. The vertical component at the Core Mantle Boundary (CMB) was used to find correlations with anomalies at the surface the Earth surface. Results have shown a rather constant westward drift and also latitude variations. It was observed that intensities follow the general decrease of the total field although the SAMA displays a predominantly non-dipolar character that is evident in the non-dipolar/total field ratios for the South Atlantic. The comparison of geomagnetic measurements by nearby Southamerican Observatories show that the SAMA influence appears as a superposition or amplification of lower wavelength phenomena such as the secular variation impulses (jerks). A downward continuation of the models was found satisfactory when compared to the stochastic inversion method. The comparison of the SAMA with other surface anomalies showed a rather independent behavior however, a comparison with the main radial component lobes at the CMB showed that all these anomalies may be interconnected. The nucleus lobes have been interpreted under the light of field generation processes, suggesting that the SAMA may originate from the combined motion of two convection columns and reverse flux regions in the outer core.

Este trabalho tem por objetivo descrever a Anomalia Magnética do Atlântico Sul (SAMA) utilizando os modelos para o período histórico (1600–1890) e também os modelos para o último século (DGRF e IGRF). Como a SAMA apresenta características de baixa intensidade do campo total e coincide com a região de intenso fluxo de partículas cósmicas, muitos problemas com objetos que orbitam a Terra (por exemplo, satélites) são detectados nessa região. São descritos os efeitos provocados pela SAMA em fenômenos espaciais. Através da análise dos modelos na forma de mapas, foram extraídos os dados de mínima intensidade para o centro da SAMA e a posição destes pontos, possibilitando conhecer a trajetória e as taxas de deriva. Os modelos foram testados na interface manto-núcleo através da componente vertical, para encontrar correlação com anomalias em superfície. Os resultados mostraram deriva para Oeste constante e variações em latitude. Foi observado que as intensidades acompanham a diminuição de todo o campo, embora a SAMA apresente caráter predominantemente não-dipolar, evidenciada pela razão entre o campo não-dipolar e o campo total no Atlântico Sul. A comparação de intensidades da SAMA com as medidas de intensidade realizadas pelos observatórios mostrou que a influência da SAMA aparece na forma de sobreposição ou amplificação de fenômenos com menor comprimento de onda, como os impulsos de variação secular (jerks geomagnéticos). A continuação para baixo dos modelos se mostrou satisfatória quando comparada com o método de inversão estocástica. A comparação da SAMA com outras anomalias em superfície mostrou independência na trajetória, porém, quando comparadas com os lóbulos principais na interface manto-núcleo, indicam que estas anomalias possam estar interligadas. Os lóbulos do núcleo foram interpretados com base nos mecanismos de geração, sugerindo que a SAMA possa ser originada através de movimentos combinados entre duas colunas de convecção e regiões de fluxo reverso no núcleo externo. / The object of this dissertation is to describe the South Atlantic Magnetic Anomaly (SAMA) using geomagnetic models for the historical period from 1600 to 1890 and also the IGRF and DGRF models for the past century. Since the SAMA presents low intensities of the total geomagnetic field that correspond to a region of intense cosmic ray particle flux, many problems with objects that orbit along this region (eg. Satelites) have been detected. The SAMA effects on space vehicles are described. The field models led to the definition of the SAMA center as the locus of minimum total field intensity and how the anomaly drifted and varied in intensity for the past four centuries. The vertical component at the Core Mantle Boundary (CMB) was used to find correlations with anomalies at the surface the Earth surface. Results have shown a rather constant westward drift and also latitude variations. It was observed that intensities follow the general decrease of the total field although the SAMA displays a predominantly non-dipolar character that is evident in the non-dipolar/total field ratios for the South Atlantic. The comparison of geomagnetic measurements by nearby Southamerican Observatories show that the SAMA influence appears as a superposition or amplification of lower wavelength phenomena such as the secular variation impulses (jerks). A downward continuation of the models was found satisfactory when compared to the stochastic inversion method. The comparison of the SAMA with other surface anomalies showed a rather independent behavior however, a comparison with the main radial component lobes at the CMB showed that all these anomalies may be interconnected. The nucleus lobes have been interpreted under the light of field generation processes, suggesting that the SAMA may originate from the combined motion of two convection columns and reverse flux regions in the outer core.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18084号 / 理博第3962号 / 新制||理||1571(附属図書館) / 30942 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 齊藤 昭則, 教授 余田 成男, 准教授 藤 浩明 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Wide arrays of applications exist for sensing systems capable of magnetic field detection. A broad range of sensors are already used in this capacity, but future sensors need to increase sensitivity while remaining economical. A promising sensor system to meet these requirements is that of magnetoelectric (ME) laminates. ME sensors produce an electric field when a magnetic field is applied. While this ME effect exists to a limited degree in single phase materials, it is more easily achieved by laminating a magnetostrictive material, which deforms when exposed to a magnetic field, to a piezoelectric material. The transfer of strain from the magnetostrictive material to the piezoelectric material results in an electric field proportional to the induced magnetic field. Other fabrication techniques may impart the directionality needed to classify the ME sensor as a vector magnetometer. ME laminate sensors are more affordable to fabricate than competing vector magnetometers and with recent increases in sensitivity, have potential for use in arrays and gradiometer configurations. However, little is known about their total field detection, the effects of multiple sensors in close proximity and the signal processing needed for target localization. The goal for this project is to closely examine the single axis ME sensor response in different orientations with a moving magnetic dipole to assess the field detection capabilities. Multiple sensors were tested together to determine if the response characteristics are altered by the DC magnetic bias of ME sensors in close proximity. And finally, the ME sensor characteristics were compared to alternate vector magnetometers. / Master of Science

Magnetic survey is a common geophysical exploration technique. By measuring the magnetic field strength at specific area, the characteristics and physical meaning of the target can be obtained through the analysis of the Earth's magnetic field anomalies within a stratigraphic zone or archaeological sites. In recent years, the marine magnetometer is employed to conduct underwater archaeological expedition at surrounding waters of Taiwan for ancient shipwrecks researching. The purpose of this study is to understand the relationship between the magnetic anomalies with the magnetic object via the various signal processing methods, included the calculation horizontal and vertical derivatives using fast Fourier transform (FFT) to eliminate the regional magnetic influence and gain the anomalies characteristics of the target itself, as well as highlight the location and boundaries of the magnetic source through the analytical signal. In addition, the Euler deconvolution implements as a tool for magnetic source inversion. The theory of Euler deconvolution was first proposed by Thompson (1982), this method is able to detect the magnetic source and estimate its locations by choosing the suitable structural index. Hsu (2002) proposed the enhanced Euler deconvolution, which is a combined inversion for structural index and source location through the use of the vertical derivative of measured data.In this study, we first generate various anomalies as testing models which are correspond with different geometric shape of magnetic source, the position and structural index for model is inversed by enhanced Euler deconvolution in both 2D and 3D.Moreover, the experiment was planned at offshore of Dalinpu in Kaohsiung, we took the CPC's pipelines as investigation objects which were buried under the seabed, than compare with sub-bottom profiler data to assess the feasibility of this method for underwater exploring applications.The most estimated results in 2D are correspond to the theory, but it does not have significant results in 3D due to the lack of observed data for the whole surface.In general, this method is concise and fast, it is fit for interpreting the magnetic data for exploring the underwater object.

Title from PDF of title page. / Document formatted into pages; contains 105 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Relative plate motion history since 30 Ma between the Pacific and the southern portion of the Nazca (Farallon) plates is examined. The history is constrained by available seafloor magnetic anomaly data and a two-minute grid of predicted bathymetry derived from satellite altimetry and shipboard sensors. These data are used to create a new plate motion reconstruction based on new magnetic anomaly identifications and finite poles of motion. The new identified magnetic isochrons and tectonic reconstruction provides greater resolution to the tectonic history between chrons 7y (24.73 Ma) and 3 (4.18 Ma) than previous interpretations. Shipboard magnetics and aeromagnetic data from over 250 expeditions were plotted and used to extrapolate magnetic anomalies picked from 2D magnetic modeling from selected cruises. Magnetic anomalies were further constrained by tectonic features evident in the predicted bathymetry. / ABSTRACT: Previously published magnetic anomaly locations consistent with this work were used where interpretation could not be constrained by 2D modeling and map extrapolation. Point locations for anomalies were used as input for calculation of finite poles of motion for chrons 10y, 7y, 6c, 5d, 5b, 5aa, 5o, 4a and 3a. An iterative process of anomaly mapping, pole calculation and anomaly point rotations was used to refine the finite poles of motion. Eleven stage poles were calculated from the nine finite poles from this study and two published instantaneous Euler vectors. Tectonic reconstructions indicate a history dominated by two major southward ridge propagation events, the first starting by 28 Ma and completed by 18 Ma. The second event initiated in association with breakup of the Farallon plate around 24 Ma and ceased by about 11 Ma. Lithosphere was transferred from Nazca to Pacific during the first event and in the opposite sense during the second. / ABSTRACT: Development of the Mendoza microplate east of the later propagator occurred at about 20 Ma and this dual spreading process appears to have lasted until about 15 Ma. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Relative plate motion history since 30 Ma between the Pacific and the southern portion of the Nazca (Farallon) plates is examined. The history is constrained by available seafloor magnetic anomaly data and a two-minute grid of predicted bathymetry derived from satellite altimetry and shipboard sensors. These data are used to create a new plate motion reconstruction based on new magnetic anomaly identifications and finite poles of motion. The new identified magnetic isochrons and tectonic reconstruction provides greater resolution to the tectonic history between chrons 7y (24.73 Ma) and 3 (4.18 Ma) than previous interpretations. Shipboard magnetics and aeromagnetic data from over 250 expeditions were plotted and used to extrapolate magnetic anomalies picked from 2D magnetic modeling from selected cruises. Magnetic anomalies were further constrained by tectonic features evident in the predicted bathymetry. Previously published magnetic anomaly locations consistent with this work were used where interpretation could not be constrained by 2D modeling and map extrapolation. Point locations for anomalies were used as input for calculation of finite poles of motion for chrons 10y, 7y, 6c, 5d, 5b, 5aa, 5o, 4a and 3a. An iterative process of anomaly mapping, pole calculation and anomaly point rotations was used to refine the finite poles of motion. Eleven stage poles were calculated from the nine finite poles from this study and two published instantaneous Euler vectors. Tectonic reconstructions indicate a history dominated by two major southward ridge propagation events, the first starting by 28 Ma and completed by 18 Ma. The second event initiated in association with breakup of the Farallon plate around 24 Ma and ceased by about 11 Ma. Lithosphere was transferred from Nazca to Pacific during the first event and in the opposite sense during the second. Development of the Mendoza microplate east of the later propagator occurred at about 20 Ma and this dual spreading process appears to have lasted until about 15 Ma.