74 resultados para Ruído sísmico
Resumo:
This study presents the Environmental Sensibility Mapping to oil spillings on the Potengi estuary - RN and neighboring coastline through remote sensing data, collecting, treatment and integration of the geomorphologic, oceanographic (temperature, salinity, density, direction and intensity), meteorological (wind speed and direction) and high resolution seismic (bathymetry and sonography) data. The Potengi river estuary is located on the eastern coastline of the Rio Grande do Norte State, being inserted in the geological context for the coastal Pernambuco-Paraíba basin and spreading over 18 km; it shelters the Natal harbor zone and an oil terminal, centralizing, therefore, important oil transport operations that can cause accidental spillings. Under the oceanographic point of view, the Potengi estuary is characterized by the absence of any expressive thermic stratification, being classified as partially mixed, B type according to Pritchard (1955), and 2 type in conformity to the stratification-circulation diagram by Hansen & Rattray (1966). Two main wind systems are responsable for the formation of wave sets that occur in the area. The dynamic tide presents, in the Natal Harbor, mean amplitude in spring and quadrature tides, with around 2.8 and 2m, respectively. The mechanism of saline tide mixing was defined through the salinity which is the main parameter for the identification of this mechanism. Important variations of the salinity mean values (36.32 psu), temperature (28.11ºC) and density (22.96 kg/m3) in the estuarine waters presented features belonging to low latitude regions. The water temperature follows the air temperature variations, in the region, with expressive daily amplitudes. In this study, the identification of the estuarine bed morphology through bathymetric and sonographic analysis, had the purpose to evaluate the influence of the superficial and bottom currents for the bottom shaping. In this way, the use of the side scan sonar showed, to be very useful in the identification of the bottom morphology and its relationship with the predominant action of the tidal currents in the Potengi estuary. Besides, it showed how the sonograms can be a support to the comparison of the several patterns derived from the local hydrodynamic variations. The holocene sediments, which fill the estuarine channel, are predominantly sandy, varying from selected, sometimes silty. The sedimentation is controlled by the environmental hydrodynamic conditions, being recognized two important textural facies: Muddy Facies and Sandy Facies. The distribution of these textural facies apparently oscillates owing to the tidal cycle and flow intensity. Each one of the above mentioned data was integrated in a Geographic Information System (GIS), from which was produced the Environmental Sensibility Map to oil spillings with Coastal Sensibility Index (CSI) to the Potengi estuary. The integrated analysis of these data is essential to oil spilling contingency plans, in order to reduce the spilling environmental consequences and to make efficient the endeavours of contention and cleaning up/removal on the Natal Harbor. This study has the aim to collaborate for the increase of informations about the estuarine environment and contribute to a better management of the question: environment/polluting loads
Resumo:
On the modern Continental Shelf to the north of Rio Grande do Norte state (NE Brazil) is located a paleo-valley, submerged during the last glacial sea-level lowstand, that marks continuation of the most important river of this area (Açu River). Despite the high level of exploration activity of oil industry, there is few information about shallow stratigraphy. Aiming to fill this gap, situated on the Neogene, was worked a marine seismic investigation, the development of a processing flow for high resolution data seismic, and the recognition of the main feature morphology of the study area: the incised valley of the River Açu. The acquisition of shallow seismic data was undertaken in conjunction with the laboratory of Marine Geology/Geophysics and Environmental Monitoring - GGEMMA of Federal University of Rio Grande do Norte UFRN, in SISPLAT project, where the geomorphological structure of the Rio paleovale Açu was the target of the investigation survey. The acquisition of geophysical data has been over the longitudinal and transverse sections, which were subsequently submitted to the processing, hitherto little-used and / or few addressed in the literature, which provided a much higher quality result with the raw data. Once proposed for the flow data was developed and applied to the data of X-Star (acoustic sensor), using available resources of the program ReflexW 4.5 A surface fluvial architecture has been constructed from the bathymetric data and remote sensing image fused and draped over Digital Elevation Models to create three-dimensional (3D) perspective views that are used to analyze the 3D geometry geological features and provide the mapping morphologically defined. The results are expressed in the analysis of seismic sections that extend over the region of the continental shelf and upper slope from mouth of the Açu River to the shelf edge, providing the identification / quantification of geometrical features such as depth, thickness, horizons and units seismic stratigraphyc area, with emphasis has been placed on the palaeoenvironmental interpretation of discordance limit and fill sediment of the incised valley, control by structural elements, and marked by the influence of changes in the sea level. The interpretation of the evolution of this river is worth can bring information to enable more precise descriptions and interpretations, which describes the palaeoenvironmental controls influencing incised valley evolution and preservation to provide a better comprehensive understanding of this reservoir analog system
Resumo:
In this dissertation it was studied the rupture characteristic of earthquakes of the Town of Cascavel CE, Northeastern Brazil. Located on the border of the Potiguar Basin, the Town of Cascavel is one of the most seismically active intraplate areas in the country. In this town, on November 20th, 1980 a 5,2mb earthquake occurred. This was the largest earthquake ever reported in Northeast Brazil. Studies of this region using instruments were possible after 1989, with several campaigns being done using seismographic networks. From the beginning of the monitoring to April 2008 more than 55,000 events were recorded. With the data collected by a network with six 3-components digital seismographic stations during the campaigns done from September 29th, 1997 to March 5th, 1998, estimates of source parameters were found fitting the displacement spectra in the frequency domain for each event. From the fitting of the displacement spectra it was possible to obtain the corner frequency ( ) c f and long period amplitude ( ) W0 . Source parameters were determined following Brune (1970) and Madariaga (1976) models. Twenty-one seismic events were analyzed (0.7 £ £ 2.1) b m in order to estimate the source dimension (r ), seismic moment ( ) M0 , static stress drop (Ds ), apparent stress ( ) a s , seismic energy ( ) S E and moment magnitude ( ) W M for each of the events. It was observed that the ratio between radiated seismic energy and moment seismic (apparent stress) increases with increasing moment and hence magnitude at the observed range. As suggested by Abercrombie (1995), also in this work there is a breakdown in the scaling for earthquakes with magnitudes smaller than three ( < 3.0) W M , so that the rupture physics is different for larger events. If this assumption is valid, the earthquakes analyzed in this work are not selfsimilar. Thus, larger events tend to radiated more energy per unit area than smaller ones.
Resumo:
The Rio do Peixe Basin is located in the border of Paraíba and Ceará states, immediately to the north of the Patos shear zone, encompassing an area of 1,315 km2. This is one of the main basins of eocretaceous age in Northeast Brazil, associated to the rifting event that shaped the present continental margin. The basin can be divided into four sub-basins, corresponding to Pombal, Sousa, Brejo das Freiras and Icozinho half-grabens. This dissertation was based on the analysis and interpretation of remote sensing products, field stratigraphic and structural data, and seismic sections and gravity data. Field work detailed the lithofacies characterization of the three formations previously recognised in the basin, Antenor Navarro, Sousa and Rio Piranhas. Unlike the classical vertical stacking, field relations and seismostratigraphic analysis highlighted the interdigitation and lateral equivalency between these units. On bio/chrono-stratigraphic and tectonic grounds, they correlate with the Rift Tectonosequence of neocomian age. The Antenor Navarro Formation rests overlies the crystalline basement in non conformity. It comprises lithofacies originated by a braided fluvial system system, dominated by immature, coarse and conglomeratic sandstones, and polymict conglomerates at the base. Its exposures occur in the different halfgrabens, along its flexural margins. Paleocurrent data indicate source areas in the basement to the north/NW, or input along strike ramps. The Sousa Formation is composed by fine-grained sandstones, siltites and reddish, locally grey-greenish to reddish laminated shales presenting wavy marks, mudcracks and, sometimes, carbonate beds. This formation shows major influence of a fluvial, floodplain system, with seismostratigraphic evidence of lacustrine facies at subsurface. Its distribution occupies the central part of the Sousa and Brejo das Freiras half-grabens, which constitute the main depocenters of the basin. Paleocurrent analysis shows that sediment transport was also from north/NW to south/SE
Resumo:
Due to its high resolution, Ground Penetrating Radar (GPR) has been used to image subsurface sedimentary deposits. Because GPR and Seismic methods share some principles of image construction, the classic seismostratigraphic interpretation method has been also applied as an attempt to interpret GPR data. Nonetheless some advances in few particular contexts, the adaptations from seismic to GPR of seismostratigraphic tools and concepts unsuitable because the meaning given to the termination criteria in seismic stratigraphy do not represent the adequate geologic record in the GPR scale. Essentially, the open question relies in proposing a interpretation method for GPR data which allow not only relating product and sedimentary process in the GPR scale but also identifying or proposing depositional environments and correlating these results with the well known Sequence Stratigraphy cornerstones. The goal of this dissertation is to propose an interpretation methodology of GPR data able to perform this task at least for siliciclastic deposits. In order to do so, the proposed GPR interpretation method is based both on seismostratigraphic concepts and on the bounding surface hierarchy tool from Miall (1988). As consequence of this joint use, the results of GPR interpretation can be associated to the sedimentary facies in a genetic context, so that it is possible to: (i) individualize radar facies and correlate them to the sedimentary facies by using depositional models; (ii) characterize a given depositional system, and (iii) determine its stratigraphic framework highligthing how it evolved through geologic time. To illustrate its use the proposed methodology was applied in a GPR data set from Galos area which is part of the Galinhos spit, located in Rio Grande do Norte state, Northeastern Brazil. This spit presents high lateral sedimentary facies variation, containing in its sedimentary record from 4th to 6th cicles caused by high frequency sea level oscillation. The interpretation process was done throughout the following phases: (i) identification of a vertical facies succession, (ii) characterization of radar facies and its associated sedimentary products, (iii) recognition of the associated sedimentary process in a genetic context, and finally (iv) proposal of an evolutionay model for the Galinhos spit. This model proposes that the Galinhos spit is a barrier island constituted, from base to top, of the following sedimentary facies: tidal channel facies, tidal flat facies, shore facies, and aeolic facies (dunes). The tidal channel facies, in the base, is constituted of lateral accretion bars and filling deposits of the channels. The base facies is laterally truncated by the tidal flat facies. In the foreshore zone, the tidal flat facies is covered by the shore facies which is the register of a sea transgression. Finally, on the top of the stratigraphic column, aeolic dunes are deposited due to areal exposition caused by a sea regression
Correlação entre contexto morfoestrutural e sismicidade nas regiões de João Câmara e São Rafael (RN)
Resumo:
This MSc thesis describes brittle deformation in two seismic zones located in north-eastern Brazil: João Câmara and São Rafael, Rio Grande do Norte State. Both areas show seismogenic faults, Samambaia and São Rafael, indicated by narrow zones of epicentres with a strike of 040o, a lenght of 30 km and 4 km, and a depth of 1-12 and 0,5-4 km, respectively. The first seismological and geological studies suggested blind faults or faults that were still in the beginning of the nucleation process. The region is under E-W-oriented compression and is underlain by Precambrian terrains, deformed by one or more orogenic cycles, which generated shear zones generally marked by strong pervasive foliation and sigmoidal shapes. The crystalline basement is capped by the Cretaceous Potiguar basin, which is also locally capped by Pliocene continental siliciclastic deposits (Barreiras Formation), and Quaternary alluvium. The main aim of this study was to map epicentral areas and find whether there are any surface geological or morphotectonic expression related to the seismogenic faults. A detailed geological map was carried out in both seismic areas in order to identify brittle structures and fault-related drainage/topographic features. Geological and morphotectonic evidence indicate that both seismogenic faults take place along dormant structures. They either cut Cenozoic rocks or show topographic expression, i.e., are related to topographic heights or depressions and straight river channels. Faults rocks in the Samambaia and São Rafael faults are cataclasite, fault breccia, fault gouge, pseudotachylyte, and quartz veins, which point to reactivation processes in different crustal levels. The age of the first Samambaia and the São Rafael faulting movement possibly ranges from late Precambrian to late Cretaceous. Both fault cut across Precambrian fabric. They also show evidence of brittle processes which took place between 4 and 12 km deep, which probably have not occurred in Cenozoic times. The findings are of great importance for regional seismic hazard. They indicate that fault zones are longer than previously suggested by seismogenic studies. According to the results, the methodology used during this thesis may also be useful in other neotectonic investigation in intraplate areas
Resumo:
The increasing use of shallow seismic methods of high resolution, for investigations of geological problems, environmental or industrial, has impelled the development of techniques, flows and computational algorithms. The practice of applying techniques for processing this data, until recently it wasn t used and the interpretation of the data was made as they were acquired. In order to facilitate and contribute to the improvement of the practices adopted, was developed a free graphical application and open source, called OpenSeismic which is based on free software Seismic Un*x, widely used in the treatment of conventional seismic data used in the exploration of hydrocarbon reservoirs. The data used to validate the initiative were marine seismic data of high resolution, acquired by the laboratory of Geology and Marine Geophysics and Environmental Monitoring - GGEMMA, of the Federal University of Rio Grande do Norte UFRN, for the SISPLAT Project, located at the region of paleo-valley of the Rio Acu. These data were submitted to the processing flow developed by Gomes (2009), using the free software developed in this work, the OpenSeismic, as well other free software, the Seismic Un*x and the commercial software ProMAX, where despite its peculiarities has presented similar results
Resumo:
The Baixa grande fault is located on the edge of the S-SW Potiguar Rift. It limits the south part of Umbuzeiro Graben and the Apodi Graben. Although a number of studies have associated the complex deformation styles in the hanging wall of the Baixa Grande Fault with geometry and displacement variations, none have applied the modern computational techniques such as geometrical and kinematic validations to address this problem. This work proposes a geometric analysis of the Baixa Fault using seismic interpretation. The interpretation was made on 3D seismic data of the Baixa Grande fault using the software OpendTect (dGB Earth Sciences). It was also used direct structural modeling, such as Analog Direct Modeling know as Folding Vectors and, 2D and 3D Direct Computational Modeling. The Folding Vectors Modeling presented great similarity with the conventional structural seismic interpretations of the Baixa Grande Fault, thus, the conventional interpretation was validated geometrically. The 2D direct computational modeling was made on some sections of the 3D data of the Baixa Grande Fault on software Move (Midland Valley Ltd) using the horizon modeling tool. The modeling confirms the influence of fault geometry on the hanging wall. The Baixa Grande Fault ramp-flat-ramp geometry generates synform on the concave segments of the fault and antiform in the convex segments. On the fault region that does not have segments angle change, the beds are dislocated without deformation, and on the listric faults occur rollover. On the direct 3D computational modeling, structural attributes were obtained as horizons on the hanging wall of the main fault, after the simulation of several levels of deformation along the fault. The occurrence of structures that indicates shortening in this modeling, also indicates that the antiforms on the Baixa Grande Fault were influenced by fault geometry
Resumo:
The gravity inversion method is a mathematic process that can be used to estimate the basement relief of a sedimentary basin. However, the inverse problem in potential-field methods has neither a unique nor a stable solution, so additional information (other than gravity measurements) must be supplied by the interpreter to transform this problem into a well-posed one. This dissertation presents the application of a gravity inversion method to estimate the basement relief of the onshore Potiguar Basin. The density contrast between sediments and basament is assumed to be known and constant. The proposed methodology consists of discretizing the sedimentary layer into a grid of rectangular juxtaposed prisms whose thicknesses correspond to the depth to basement which is the parameter to be estimated. To stabilize the inversion I introduce constraints in accordance with the known geologic information. The method minimizes an objective function of the model that requires not only the model to be smooth and close to the seismic-derived model, which is used as a reference model, but also to honor well-log constraints. The latter are introduced through the use of logarithmic barrier terms in the objective function. The inversion process was applied in order to simulate different phases during the exploration development of a basin. The methodology consisted in applying the gravity inversion in distinct scenarios: the first one used only gravity data and a plain reference model; the second scenario was divided in two cases, we incorporated either borehole logs information or seismic model into the process. Finally I incorporated the basement depth generated by seismic interpretation into the inversion as a reference model and imposed depth constraint from boreholes using the primal logarithmic barrier method. As a result, the estimation of the basement relief in every scenario has satisfactorily reproduced the basin framework, and the incorporation of the constraints led to improve depth basement definition. The joint use of surface gravity data, seismic imaging and borehole logging information makes the process more robust and allows an improvement in the estimate, providing a result closer to the actual basement relief. In addition, I would like to remark that the result obtained in the first scenario already has provided a very coherent basement relief when compared to the known basin framework. This is significant information, when comparing the differences in the costs and environment impact related to gravimetric and seismic surveys and also the well drillings
Resumo:
The seismic reflection is used on a large scale in oil exploration. In case of marine acquisition the presence of high impedance contrast at the interfaces water/air generates multiple reflections events. Such multiple events can mask primary events; thus from the interpretational viewpoint it is necessary to mitigate the multiples. In this manuscript we compare two methods of multiple attenuation: the predictive multichannel deconvolution (DPM) and the F-K filtering (FKF). DPM is based in the periodicity of the multiples while FKF is based in multiples and primaries splitting in F-K domain. DPM and FKF were applied in common-offset and CDP gathers, respectively. DPM is quite sensible to the correct identification of the period and size of the filter while FKF is quite sensible to an adequate choice of the velocity in order to split multiples and primaries events in the F-K domain. DPM is a method that is designed to act over a specific event. So, when the parameters are well selected, DPM is very efficient in removing the specified multiple. Then DPM can be optimized by applying it several times, each time with a different parameterization. A deficiency of DPM occurs when a multiple is superposed to a primary event: in this situation, DPM can attenuate also the primary event. On the other hand, FKF presents almost the same performance to all multiples that are localized in the same sector of the F-K domain. The two methods can be combined in order to take advantage of their associated potentials. In this situation, DPM is firstly applied, with a focus in the sea bed multiples. Then FKF is applied in order to attenuate the remaining multiples
Resumo:
The Camorim Oilfield, discovered in 1970 in the shallow water domain of the Sergipe Sub-basin, produces hydrocarbons from the Carmópolis Member of the Muribeca Formation, the main reservoir interval, interpreted as siliciclastics deposited in an alluvial-fluvial-deltaic context during a late rifting phase of Neoaptian age, in the Sergipe-Alagoas Basin. The structural setting of the field defines different production blocks, being associated to the evolution of the Atalaia High during the rift stage and subsequent reactivations, encompassing NE-SW trending major normal faults and NWEW trending secondary faults. The complexity of this field is related to the strong facies variation due to the interaction between continental and coastal depositional environments, coupled with strata juxtaposition along fault blocks. This study aims to geologically characterize its reservoirs, to provide new insights to well drilling locations in order to increase the recovery factor of the field. Facies analysis based on drill cores and geophysical logs and the 3D interpretation of a seismic volume, provide a high resolution stratigraphic analysis approach to be applied in this geodynamic transitional context between the rift and drift evolutionary stages of the basin. The objective was to define spatial and time relations between production zones and the preferential directions of fluid flow, using isochore maps that represent the external geometry of the deposits and facies distribution maps to characterize the internal heterogeneities of these intervals, identified in a 4th order stratigraphic zoning. This work methodology, integrated in a 3D geological modelling process, will help to optimize well drilling and hydrocarbons production. This methodology may be applied in other reservoirs in tectonic and depositional contexts similar to the one observed at Camorim, for example, the oil fields in the Aracaju High, Sergipe Sub-basin, which together represent the largest volume of oil in place in onshore Brazilian basins
Resumo:
Microseisms are continuous vibrations pervasively recorded in the mili Hertz to 1 Hz frequency range. These vibrations are mostly composed of Rayleigh waves and are strongest in the 0.04 to 1 Hz frequency band. Their precise source mechanisms are still a matter of debate but it is agreed that they are related to atmospheric perturbations and ocean gravity waves. The Saint Peter Saint Paul Archipelago (SPSPA) is located in the equatorial region of the Atlantic Ocean about 1,100 km distant from the Brazilian northeastern coast. The SPSPA is composed by a set of several small rocky formations with a total area of approximately 17,000 m². Due to its remote distance from the continent and the lack of cultural noise, this location is a unique location for measuring microseismic noise and to investigate its relation with some climate and oceanographic variables. In the SPSPA we have recorded both primary microseisms (PM) at 0.04 – 0.12 Hz and the secondary microseisms (SM) at 0.12 – 0.4 Hz during 10 months in 2012 and 2013. Our analysis indicates a good correlation between the microseismic noise in the region and a seasonal dependency. In particular, the winter in the northern hemisphere. We have also shown that most of the PM is generated in the SPSPA itself. The SM source location depends with the seasonal climatic and oceanographic variables in the northern hemisphere
Resumo:
The Brazilian Environmental Data Collecting System (SBCDA) collects and broadcasts meteorological and environmental data, to be handled by dozens of institutions and organizations. The system space segment, composed by the data collecting satellites, plays an important role for the system operation. To ensure the continuity and quality of these services, efforts are being made to the development of new satellite architectures. Aiming a reduction of size and power consumption, the design of an integrated circuit containing a receiver front-end is proposed, to be embedded in the next SBCDA satellite generations. The circuit will also operate under the requirements of the international data collecting standard ARGOS. This work focuses on the design of an UHF low noise amplifier and mixers in a CMOS standard technology. The specifi- cations are firstly described and the circuit topologies presented. Then the circuit conception is discussed and the design variables derived. Finally, the layout is designed and the final results are commented. The chip will be fabricated in a 130 nm technology from ST Microelectronics.
Resumo:
Inside the Borborema Province the Northwestern Ceará (NC) is one of the most seismic active regions. There are reports of an earthquake occurred in 1810 in the Granja town. On January, 2008 the seismic activity in NC has increased and it was deployed a seismographic network with 11 digital stations. In 2009, another earthquake sequence began and it was deployed another seismographic network in the Santana do Acaraú town with 6 stations. This thesis presents the results obtained by analyzing the data recorded in these two networks. The epicentral areas are located near the northeastern part of the Transbrasiliano Lineament, a shear zone with NE-SW-trending that cuts the study area. The hypocenters are located between 1km and 8km. The strike-slip focal mechanisms were found, which is predominant in the Borborema Province. An integration of seismological, geological and geophysical data was performed and it show that the seismogenic faults found are oriented in the same direction to the local brittle structures observed in field and magnetic lineaments. The SHmax (maximum compressional stress) direction in NC was estimated using an inversion of seven focal mechanisms. The horizontal maximum compression stress (σ1 = 300°) with orientation NW-SE and extension (σ3 = 210°) with NE-SW and σ2 vertical. These results are consistent with results of previous studies. The seismic activity recorded in NC is not related to a possible reactivation of the Transbrasiliano Lineament, by now.
Resumo:
The reverse time migration algorithm (RTM) has been widely used in the seismic industry to generate images of the underground and thus reduce the risk of oil and gas exploration. Its widespread use is due to its high quality in underground imaging. The RTM is also known for its high computational cost. Therefore, parallel computing techniques have been used in their implementations. In general, parallel approaches for RTM use a coarse granularity by distributing the processing of a subset of seismic shots among nodes of distributed systems. Parallel approaches with coarse granularity for RTM have been shown to be very efficient since the processing of each seismic shot can be performed independently. For this reason, RTM algorithm performance can be considerably improved by using a parallel approach with finer granularity for the processing assigned to each node. This work presents an efficient parallel algorithm for 3D reverse time migration with fine granularity using OpenMP. The propagation algorithm of 3D acoustic wave makes up much of the RTM. Different load balancing were analyzed in order to minimize possible losses parallel performance at this stage. The results served as a basis for the implementation of other phases RTM: backpropagation and imaging condition. The proposed algorithm was tested with synthetic data representing some of the possible underground structures. Metrics such as speedup and efficiency were used to analyze its parallel performance. The migrated sections show that the algorithm obtained satisfactory performance in identifying subsurface structures. As for the parallel performance, the analysis clearly demonstrate the scalability of the algorithm achieving a speedup of 22.46 for the propagation of the wave and 16.95 for the RTM, both with 24 threads.