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5th International Congress of the Brazilian Geophysical Society
- Conference date: 28 Sep 1997 - 03 Oct 1997
- Location: São Paulo, Brazil
- Published: 07 November 1997
341 - 360 of 416 results
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Tropospheric and Stratospheric Conductivity Measurements in Brazil
Authors M.M.F. Saba, O. Pintor Jr., I.R.C.A. Pinto and O. Mendes Jr.Conductivity measurements were carried out during a balloon flight launched from Cachoeira Paulista, Brazil (22°44' S, 44°56' W) on Jan 26, 1994. For the first time negative and positive conductivity profiles with altitude were obtained in Brazil. Along its trajectory the balloon passed over three thunderstorms, as identified by video on-board images. The data give an unique opportunity to study the stratospheric conductivity variations.
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The Solar Cycle and Cosmic Ray Particles Have Direct Influence on Stratospheric Ozone Variation?
We analyze in this work three available sets of stratospheric ozone measurements obtained by ground UV sun spectrophotometer type Dobson and low energy stratospheric cosmic rays in the period from 1957 until 1995. By the analysis of these sets of ozone data, we can see a decreasing intensity at all these latitudes (Belsk, Tbilisi and C. Paulista), given a global mean rate - 10 % during the last three solar cycles. We saw also correlations with cosmic rays measurements in the stratosphere, ozone variations and sunspot number.
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Influęncia da Radiaçăo Solar no Ser Humano
By H.A. PonzioAs radiaçőes năo ionizantes, que compreendem as ultravioleta (UV), o espectro visível (EV) e as infravermelhas (IV), săo as principais responsáveis pelos efeitos fotobiológicos provocados pelas emissőes solares nos seres vivos. As UV-B tem limitada capacidade de penetraçăo na pele e exercem seus efeitos na camada basal e acima dela; săo eritematógenas e, a longo prazo, as principais responsaveis pelo câncer de pele.
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Heat Transport Estimates in the Surface Layer of the Antarctic Polar Front Using a Satellite Tracked Drifter - First Results
Authors M. Kampel, M.R. Stevenson and A.R. AssireuThe oceans play an essential role in the dynamic climate system, via 3 distinct mechanisms: 1) they absorb and exchange carbon dioxide with the atmosphere; 2) they exchange heat, water vapor and momentum with the atmosphere. The ocean circulation redistribute heat, fresh water and dissolved chemicals around the globe; and 3) they capture heat, absorbed at the surface, in the deepest regions for periods of a thousand years or more through vertical circulation and convective mixing.
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Latitude Dependence of the QBO and QTO Characteristics of Total Ozone Measured by Toms
Authors R.P. Kane, Y. Sahai and C. CasicciaThe 12-month moving averages of TOMS total ozone data for 14 years (1979-1992) were examined for QBO and QTO (quasibiennial and quasi-triennial oscillations) and compared with stratospheric low latitude zonal wind and equatorial eastern Pacific seasurface temperature (SST). The equatorial ozone had a strong QBO of period -30 months and its maxima tallied with westerly wind maxima. At other latitudes, the ozone maxima spacings were often different from 30 months, more so in the northern hemisphere. A spectral analysis showed that both hemispheres had one peak at -20 months and another at -30 months, only up to -50° latitude. At higher latitudes, these peaks shifted to -23 months and -36 months. For 0-50°, the -30 month periodicity was symmetric in the northern and southern latitudes and showed a gradual phase shift. The northern hemisphere had an additional periodicity at -4 years, roughly matching the SST.
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Observations of Atmospheric Ozone and UV -B Radiation in Brazil
Authors Y. Sahai, V.W.J.H. Kirchhoff and N.M. Paes LemeDuring recent years atmospheric ozone has become a topic of great concern. This stems from the fact that there are serious implications of the anthropogenic sources depleting the stratospheric ozone layer. Observations of atmospheric ozone started in Brazil on a routine basis in May 1974, when Dobson spectrophotometer (n° 114) was installed at Cachoeira Paulista (23° S, 45° W), Sao Paulo.
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Alteraciones de la Columna de Ozono en Punta Arenas (Chile) y la Influencia del "Agujero de Ozono
Authors C. Casiccia and V.W.J.H. KirchhoffDesde agosto de 1992 está operando en Punta Arenas (53,2°S;70,9°W) un espectrofotómetro Brewer, modelo MK-IV (serie 068). Este es el primer instrumento instalado en Chile para observaciones sistemáticas a largo plazo, con el propósito de estudiar el comportamiento y la evolución de la capa de ozono, en la zona poblada más cerca de la Antártica, donde desde hace unos ańos, a comienzo de la primavera Austral se manifiesta el fenómeno de la formación del "Agujero de Ozono Antártico" (AOA). En este trabajo se presenta un análisis de practicamente cinco ańos de mediciones hechas con el espectrofotómetro Brewer, como también un análisis de los meses de septiembre y octubre (1992-1996), de la evolución de la capa de ozono. Se muestran las mayores disminuciones detectadas hasta este momenta sobre Punta Arenas, como por ejemplo el día 17 de octubre de 1994 cuando se midieron 145,8UD (Unidades Dobson), que es el valor más bajo medido, en cinco ańos, equivalente aproxirnado a casi el 60% abajo de la media normal. Se muestra además los resultados de los primeros sondajes de ozono realizados con sondas ECC, realizados en Punta Arenas en octubre de 1995, para analisis de la distribuici6n de ozono con la altura.
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Mapeamento Geoeletrico do Aterro da Lamenha Pequena (Curitiba - PR)
Authors A. Rigoti, V. Pinheiro Jr. and J.R. de GóisO Aterro da Lamenha Pequena é formado por duas áreas de deposiçăo de lixo, denominadas vertente suI (VS) e vertente norte (VN) localizadas na divisa dos municípios de Curitiba e Almirante Tamandaré (Fig. la). A disposiçăo dos resíduos na área se deu inicialmente na VS na decada de 1960, sendo o ate rro desativado definitivamente em 1989. Com superfície de cerca de 30.000 m2 , a VS concentra em torno de 335.000 m3 de residuos, enquanto que a VN com 70.000 m2 , aloja urn volume próximo de 475.000 m3.
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Estudio Geofísico - Geotécnico en la Ruta Nacional 150 Ischigualasto - Bermejo
Authors N.A. Ponti, A.L. Imhof, S.A. Pastore, A.E. Guell and G.O. FantonSe sintetizan tareas, resultados y conclusiones del estudio geofísico-geotécnico llevado a cabo sobre la traza de la Ruta Nacional 150, tramo Ischigualasto - Bermejo, de 36.000 metros de extensión, que une los Departamentos de Valle Fertil y Jachal, al N.E de la provincia de San Juan, Republica Argentina.- Se efectuó un relevamiento geológico, sondeos eléctricos verticales y lineas de refracción sísmica a lo largo de la traza proyectada.
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Aplicaciones Prácticas del Método de Resistividad en Arqueología - Santa Fe - Republica Argentina
More LessEl estudio de investigación geofísica fué realizado en dos solares pertenecientes a familias de conquistadores que habitaron la ciudad de Sta. Fé La Vieja, entre 1576 - 1660. Dicha ciudad está situada 80 Km al Noreste de la ciudad capital de la Provincia de Santa Fé - Rep. Argentina -. Con ese objeto aplicó el metodo de prospección geoeléctrica, el que permitió aportar datos geofísicos de gran importancia para el logro de los siguientes objetivos : - Delimitación de las ruinas (tejas de techo, partes de muros, maderas, etc.). En síntesis materiales que se emplearon en la construcción de las viviendas. - Situación y ubicación de los muros laterales y frontales de las edificaciones.
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Estudio Integrado del Area de Pato, Norte de Oficina, Cuenca Oriental de Venezuela
Authors J. Delgado, A. Ramos, E. Roa and L. HernandezEI área de estudio esta localizada en la zona de Pato, ubicada al norte del Area Mayor de Oficina, donde la Formación Oficina y la parte superior de la Formación Merecure, presentan prospectos limitados por fallas, conformando trampas estructurales similares a las encontradas en los campos tradicionales al sur de la zona de Pato y otros con características estratigráficas, como los definidos en este estudio, los cuales pertenecen a sistemas de cuńas progradantes de bajo nivel (Lowstand Wedge).
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Recent Results of UV -B Measurements in Brazil
More LessA network of UV-B meters has been organized and distributed in Brazil in association with studies of the stratospheric ozone layer and in an effort to increase public awareness of excess UV-B radiation on the human skin. In order to make UV-B measurements more accessible to the people, the UV Index has been calculated in specific cases. Three different kinds of UV-B meters are used. The most sofisticated instruments can measure very narrow spectral ranges, and they can do it almost unattended by operators. Simultaneously they measure stratospheric ozone, Sulfur dioxide and Nitrogen dioxide; these are the Brewer spectrophotometers, six of which are presently part of the network. A second class of instruments is simpler but can also make spectral measurements at different wavelengths; the network has now three GUV meters in this category. And in the third class of instruments there are the UV-Biometers, which are UV-B integrating instruments, less expensive and very convenient for different applications and interpolation purposes. There are presently 8 such instruments in operation. The whole network has recently also expanded to neighbor collaborating countries, Chile and Bolivia. Southern Chile is very interesting for observations of the Antarctic Ozone Hole, and its consequences in terms of increased UV-B; and in Bolivia, the high Andes mountains receive high doses of UV-B and UV-A, because of the altitude above sea level. We will show some of these UV results, and show differences in various regions of Brazil.
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Disturbed Days
More LessDisturbed days characterized by the geomagnetic index AA * are considered. According to the present results, the intensity of the most disturbed days will increase during the next solar cycles.
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Levantamentos Geofísicos ao Largo de 16 Praias do Litoral de 8 Estados Brasileiros
Authors M.A. Gorini, C.G. Silva, E.A. Souza, F.Z. Oliver and M.N. PrazeresEntre os meses de abril e agosto de 1995 a G.G.G. Consultoria Ltda. executou uma série de levantamentos geofísicos de alta resoluçăo em 16 praias do litoral de 8 estados brasileiros, visando a instalaçăo de urn cabo submarino de fibra ótica. Estes estudos proporcionaram urn conhecimento das características geomorfológicas do fundo submarino da plataforma continental mais interna entre os estados do Rio de Janeiro e Rio Grande do Norte.
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WIPEOUTS A Resposta Acústica da Presença de Gás nos Sedimentos do Fundo Marinho da Bacia de Campos
Authors C.Y. Murakami, D.J. Miller and W. de Almeida JúniorA Petrobras através da equipe da Geręncia de Geologia Marinha da E&P-BC com o objetivo de conhecer e elaborar modelos para auxiliar a exploraçăo de petróleo e instalaçăo de equipamentos de perfuraçăo e produçăo, tern realizado mapeamentos do fundo marinho com os dados de sonar de varredura lateral e sísmica monocanal de alta resoluçăo de 3,5kHz (SBP - subbottom profile) na Bacia de Campos.
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Interference Slow Wave in Poro-Acoustic Biot Layer and Its Potential for the Detection of Subtle Traps
Authors Pavel Krauldis and Marco A. Barsottelli BotelhoThis work proves the existence of an Interference Slow Wave (ISW) in Biot porous acoustic media. The presence of ISW is theoretically established by solving the Biot equation considering a model of one horizontal layer surrounded by two elastic half spaces. The low attenuation of ISW on lower seismic frequencies and its polarizibility in the direction of the layer makes this wave potentially useful for detecting reservoirs consisting of a saturated sandstone layer inside shale in cross-hole surveys.
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Acquisition and In-Field Processing on Bottom Cable 3-D Seismic Surveys
Authors E. Bargaud, M. Denis, J. Meunier and J.J. PostelTwo 3-D seismic surveys located off the north coast of Java between Jakarta and Cirebon, were acquired by CGG for ARCO Indonesia in conjunction with PERT AMINA.One covered 105 square kilometers in the transition zone near Cilamaya. For operational and accessibility reasons, hydrophone bottom cables were used. Geophones in marsh cases on shore and in very shallow water provided 3-D coverage beneath the shoreline from shallow marine sources. The other survey covered 189 square kilometers in a producing oil field 35 kilometers north of Pamanukan in water depths of 35 to 45 meters. The presence of many platforms, tankers, and moorings made the dual-sensor bottom cable technique ideal for this area. A patch acquisition geometry was chosen for both surveys because of its ability to provide shallow coverage and the desired data distributions under obstacles, and for its operational simplicity among the obstructions. Bottom cables were used to allow deployment near the platforms and for their low noise characteristics. Acoustic positioning provided accurate receiver positions, while minimizing surface buoys, a major source of noise. Finally, extensive QC procedures, including DGPS monitoring, positioning control, attribute mapping, and seismic processing were used to provide feedback to the crew, allowing them to optimize operations. During one survey, two field-processed, 3-D migrated data blocks were delivered to the interpreter for preliminary mapping within a week after recording the last shots on each of those blocks.
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The Challenge of Acquisition and Processing in Mountainous Thrust Areas
Authors E. Bargaud, M. Denis, J. Meunier and J.J. PostelThe issues involved in this difficult problem can be divided into 3 categories: - Adapted field parameters - Adapted logistics with lightweight equipment - Adapted processing with special techniques
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Estimativa do Fator Q em A" guas Profundas: Implicacoes nos Parametres de Aquisicao
Os dados sísmicos de superfície registrados em áreas de águas profundas na bacia sedimentar focalizada neste trabalho possuem urn 'conteúdo de freqüęncies geralmente inferior a dados equivalentes provenientes de outras áreas, inclusive áreas terrestres. Em consequęncia disto, a escolha dos parâmetres de aquisiçăo para estas áreas depende de uma avaliaçăo das propriedades dissipativas dos sedimentos sobrepostos aos reservatórios af presentes. Neste trabalho, essas propriedades da subsuperfície sao avaliadas de uma forma simples, onde o fator Q é estimado a partir da curva de drift proveniente de dados de poço. Comparaçőes nos domínios da freqüęncia e do tempo entre formas de onda geradas pela modelagem direta e suas eqüivalentes estimadas a partir de dados sísmicos de superfície propiciaram a validaçăo das estimativas obtidas. Săo, tarnbém, discutidas as implicaçőes que os efeitos dissipativos estimados tęm sobre a aquisiçăo de dados nesta área.
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Seismic Crosswell Tomography: A Gauss-Newton Type Method Based on B-splines for Velocity Field Parametrization. 2nd Part: Applications
More LessTwo applications of the Gauss-Newton type method introduced in the companion paper (Soares Filho, 1997) are presented. The first one aims to exhibit its robustness in terms of different starting points. Speciffically, the target model ("Z model") is effectively reconstructed from three very different initial models. The second application shows a straightforward consequence of small condition numbers. The stability of the method is confirmed using contaminated traveltimes with Gaussian modulated additive errors.
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