A recently identified 30 km by 7.2 km subsurface stratigraphic uplift, called the Charleston uplift, exhibits 36 m offset of Paleogene-Quaternary unconformity based on shallow borehole data. Two seismic soundings demonstrated relief in Paleozoic and Cretaceous reflectors across the northern boundary of the uplift, suggesting a structural origin rather than an erosional origin. This study collected and analyzed 18 additional shallow seismic soundings to confirm Paleozoic and Cretaceous offset across the boundaries of the uplift, to better constrain the surface trace of the uplift, and to examine potential extension into western Kentucky. One ground penetrating radar profile was taken in western Kentucky to image recent deformation. Results confirm Paleozoic and Cretaceous offset along the boundaries of the uplift and indicate extension of the uplift into western Kentucky, although recent deformation was unconfirmed by the radar profile. These data support a structural origin. The N46°E trend of the uplift as well as its coincidence with contemporary microseismicity suggest that this feature may be related to the New Madrid seismic zone, specifically the New Madrid North fault, which may have implications for hazard assessment, as well as possible a reevaluation of the epicenters for the 23 January 1812 Mw ≥ 7.0 event.

Orientador: Martin Tygel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Cientifica / Made available in DSpace on 2018-08-22T06:13:33Z (GMT). No. of bitstreams: 1 CostaFilho_CarlosAlbertoda_M.pdf: 3131395 bytes, checksum: f8687abfc7e346fdd8e6dc40746526e8 (MD5) Previous issue date: 2013 / Resumo: As reflexões de ondas sísmicas na subsuperfície terrestre podem ser colocadas em duas categorias disjuntas: reflexões primárias e múltiplas. Reflexões primárias carregam informações pontuais sobre um refletor específico, enquanto reflexões múltiplas carregam informações sobre interfaces e pontos de reflexão variados. Consequentemente é usual tentar atenuar reflexões múltiplas e trabalhar somente com reflexões primárias. Neste trabalho, a teoria de ondas acústicas é desenvolvida somente a partir da equação da onda. Um resultado que demonstra como a propagação de ondas acústicas pode ser descrita somente com uma única multiplicação por matriz é exposta. Este resultado permite que um algoritmo seja desenvolvido que, em teoria, pode ser usado para remover todas as reflexões múltiplas que refletiram na superfície pelo menos uma vez. Uma implementação prática deste algoritmo é mostrada. Por conseguinte, a teoria de análise de componentes independentes é apresentada. Suas considerações teóricas e práticas são abordadas. Finalmente, ela é usada em conjunção com o método de eliminação de múltiplas de superfície para atenuar múltiplas de quatro dados diferentes. Estes resultados são então analisados e a eficácia do método é avaliada / Abstract: The reflections of seismic waves in the subsurface of the Earth can be placed under two disjoint categories: primary and multiple reflections. Primary reflections carry pointwise information about a specific reflector while multiple reflections carry informations about various interfaces and reflection points. Consequently, it is customary to attempt to attenuate multiple reflections and work solely with primary reflections. In this work, the theory of acoustic waves is developed solely from the wave equation. A result that shows how acoustic wave propagation can be described as a single matrix multiplication is exposed. This result enables one to develop an algorithm that, in theory, can be used to remove all multiple reflections that have reflected on the surface at least once. The practical implementation of this algorithm is shown. Thereafter, the theory of independent component analysis is presented. Its theoretical and practical considerations are addressed. Finally, it is used in conjunction with the surface-related multiple elimination method to attenuate multiples in four different datasets. These results are then analyzed and the efficacy of the method is evaluated / Mestrado / Matematica Aplicada / Mestre em Matemática Aplicada

La bordure septentrionale du Vénézuela (bordure méridionale de la Plaque Caraïbe) correspond pour l’essentiel à un relais de grandes failles décrochantes actives, génératrice d’une marge escarpée et accidentée (Sud de la Mer Caraïbe, Fosse et Golfe de Cariaco, Fig. 1). Cette région est donc exposée à trois sources d’aléas naturels : 1) séismes et effets directs, 2) tsunamis (liés à ces failles, à l’activité plus lointaine des Arcs Antillais, ou à des glissements sous-marins), 3) glissements et coulées aériens, parfois liés à des événements climatiques brutaux (cf. flash flood de Vargas, Décembre 1999). Le deuxième et le troisième type de phénomènes affectent directement la sédimentation soit marine (littoral et plateforme) soit lagunaire ou lacustre. Par ailleurs, les dernières variations globales (rapides) du niveau marin ont subdivisé et structuré l’empilement sédimentaire.La partie récente de ces dépôts (env. 150 000 à 200 000 ans) a fait l’objet de deux campagnes préliminaires d’imagerie sismique à haute résolution, la première consacrée à la partie orientale (Golfe de Cariaco; Audemard et al., 2007 ; Van Daele et al., 2010) et la seconde au littoral central (entre Cabo Codera et la Golfe Triste, Fig. 2). Cette seconde mission sera complétée par une nouvelle acquisition d’imagerie et la prise de carottes courtes en mer et dans les lagunes côtières. L'interprétation des sections sismiques et l'analyse sédimentologique des carottes sera utilisé pour ce travail de thèse avec un double but : 1) reconstituer l’évolution générale de la sédimentation sur la marge, et l’influence des changements environnementaux globaux, 2) connaître la distribution géographique et dans le temps (pour une période d’au moins 100 000 ans) des phénomènes catastrophiques majeurs (séismes, tsunamis, flash floods) qui se sont intercalés dans cette sédimentation. L’impact possible de la superposition de phénomènes externes et sismo-tectoniques (cf. récent séismes de Tucacas pendant un épisode pluvieux) et la localisation des zones à risques pour les tsunamis, seront modélisés et discutés. / The northern border of Venezuela (southern border of the Caribbean Plate) corresponds essentially to a relay of large active strike-slip faults, generating a steep and rugged margin (South of the Caribbean Sea, Pit and Gulf of Cariaco, Fig. 1). This region is therefore exposed to three sources of natural hazards: 1) earthquakes and direct effects, 2) tsunamis (related to these faults, to the more distant activity of the West Indies bows, or to submarine landslides), 3) slips and airflows, sometimes linked to sudden climatic events (see Vargas flash flood, December 1999). The second and third types of phenomena directly affect sedimentation, whether marine (littoral and platform), lagoon or lacustrine. In addition, the latest global (fast) changes in the sea level have subdivided and structured the sedimentary stack.The recent part of these deposits (about 150 000 to 200 000 years ago) was the subject of two preliminary high resolution seismic imaging campaigns, the first devoted to the eastern part (Gulf of Cariaco, Audemard et al. 2007, Van Daele et al., 2010) and the second at the central coast (between Cabo Codera and the Sad Gulf, Fig. 2). This second mission will be complemented by a new imaging acquisition and the taking of short cores at sea and in coastal lagoons. The interpretation of the seismic sections and the sedimentological analysis of the cores will be used for this work of thesis with a double aim: 1) to reconstruct the general evolution of the sedimentation on the margin, and the influence of the global environmental changes, 2) to know the geographical distribution and over time (for a period of at least 100,000 years) major catastrophic phenomena (earthquakes, tsunamis, flash floods) that have interbedded in this sedimentation. The possible impact of the superposition of external and seismo-tectonic phenomena (see the recent Tucacas earthquakes during a rainy episode) and the location of tsunami risk areas will be modeled and discussed.

A vast area of the northeastern Great Basin of the western USA was inundated by a succession of Plio-Pleistocene lakes, including Lake Bonneville (28 ka to 12 ka). The Pilot Valley playa, located just east of the Utah-Nevada border near Wendover, Utah, within the eastern Basin and Range Province, represents an 8 to 16 km wide and ~50 km long remnant of these lakes. The playa corresponds to the upper surface of a closed basin that is delimited by two mountain ranges, which are mantled by recent alluvial fans over which the playa sediments have prograded. In order to investigate the interaction of Plio- Pleistocene lake sedimentation and alluvial fan development, high-resolution seismic reflection profiles have been acquired near the base of both the west-bounding and the east-bounding ranges. On the western side of the basin, the seismic profiles provide images of sub-horizontal playa sediments prograding over the inclined alluvial fans. Theboundary between the playa and fan sediments is marked by a prominent angular unconformity. Seismic images from the eastern side of the basin reveal a markedly different structural and stratigraphic style with down-to-the-basin normal faulting of relatively shallow Paleozoic bedrock overlain by alluvial fan deposits, which are in turn on-lapped by a thin veneer of playa sediments. The results contained herein reveal for the first time the stratigraphic relationships between Quaternary pluvial sediments as a shoreline depositional facies and the adjacent bounding fan deposits. Post-stack reprocessing of lower-resolution but deeper penetration seismic data located in an analogous basin to the southwest, provides a likely context for the Pilot Valley seismic data. The new geophysical images, when integrated with available geologic mapping and limited well control, aid in constraining how deep aquifers are locally recharged from an adjacent range. The results also clearly demonstrate the strong structural asymmetry of the range and playa system, which is consistent with a classic half-graben structure. Lastly, this study demonstrates the utility of the shallow seismic reflection method as a tool to provide high-resolution sub-surface images in the geophysically challenging environment of Basin and Range geology.

No description available.

Complex trace attribute analysis has been applied to 24-fold VIBROSEIS reflection data acquired on the Atlantic Coastal Plain near Charleston, S. C., to yield an expanded interpretation of a Mesozoic basin concealed beneath Coastal Plain sediments. Complex trace attributes express the seismic trace in terms of a complex variable and emphasize different components of the original seismogram. Attributes derived from synthetic seismograms of thin beds are used to interpret the patterns observed on the real data. Complex trace attributes derived from the original seismic trace complement the interpretation of a Mesozoic basin originally imaged by conventional data. The combination of single-sweep recording and use of complex trace attributes is believed to support an interpretation of a transition from basin border conglomerates into finer-grained siltstones nearer to the center of the basin. / Master of Science / incomplete_metadata

An extensive multi-channel seismic dataset acquired between 1970 and 1990 by Oljeprospektering AB (OPAB) has recently been made available by the Geological Survey of Sweden (SGU). This thesis summarizes four papers, which utilize this largely unpublished dataset to improve our understanding of the geology and CO2 storage capacity of the Baltic and Hanö Bay basins in southern Sweden. A range of new processing workflows were developed, which typically provide an improvement in the final stacked seismic image, when compared to the result obtained with the original processing. A method was developed to convert scanned images of seismic sections into SEGY files, which allows large amounts of the OPAB dataset to be imported and interpreted using modern software. A new method for joint imaging of multiples and primaries was developed, which is shown to provide an improvement in signal to noise for some of the seismic lines within the OPAB dataset. For the first time, five interpreted regional seismic profiles detailing the entire sedimentary sequence within these basins, are presented. Depth structure maps detailing the Outer Hanö Bay area and the deeper parts of the Baltic Basin were also generated. Although the overall structure and stratigraphy of the basins inferred from the reprocessed OPAB dataset are consistent with previous studies, some new observations have been made, which improve the understanding of the tectonic history of these basins and provide insight into how the depositional environments have changed throughout time. The effective CO2 storage potential within structural and stratigraphic traps is assessed for the Cambrian Viklau, När and Faludden sandstone reservoirs. A probabilistic methodology is utilized, which allows a robust assessment of the storage capacity as well as the associated uncertainty. The most favourable storage option in the Swedish sector of the Baltic Basin is assessed to be the Faludden stratigraphic trap, which is estimated to have a mid case (P50) storage capacity of 3390 Mt in the deeper part of the basin, where CO2 can be stored in a supercritical phase.

The morphology of Lake Sibaya is a product of an ancient fluvial system that drained a coastal landscape dominated by aeolian processes. The sedimentary processes within the lake are driven by wind generated currents. The dominant sedimentary process is one of lake segmentation, whereby prograding bedforms isolate the lake into smaller water bodies. The prograding bedforms include cuspate forelands and sand spits. The size and mobility of these bedforms is a function of sediment availability and current regime. The bathymetry of Lake Sibaya is discussed, with emphasis on geomorphic features derived from the ancient aeolian landscape as well as features related to modern sedimentary processes. The presence of underwater knickpoints and terraces indicate that lake level fluctuations have been common in Lake Sibaya. It is during lake highstands that large volumes of sand are eroded from aeolian dunes which surround the lake and made available for shoreline progradation. Ancient dune topography is preserved to depths of 20 m below water-level within the lake. Surface sediment distribution maps were compiled from 515 grab samples and thirteen core samples. Fine grained, well sorted, coarse skewed quartz sand comprises the majority of the surface area of the lake floor. Gyttja is the other dominant sediment type and accumulates in palaeovalleys and depressions on the lake floor. Sediment distribution in Lake Sibaya is discussed in terms of modern lacustrine processes as well as inherited sedimentary characteristics. The stratigraphy of the sediments underlying Lake Sibaya was investigated using a Uni-Boom seismic profiling system. Seismic profiles were compiled by identifying acoustically reflective surfaces that show regional development. Thirteen seismic overlays were prepared, and are illustrated as west - east and north - south seismic profiles. Five sequences ranging in age from late Cretaceous to Holocene were identified from the seismic profiles, and are described in terms of sequence stratigraphic principles. The seismic sequences were interpreted within a lithostratigraphic framework and are presented as a series of idealised geological sections. Thirteen sediment cores were collected from the Lake Sibaya area in order to ascertain the accuracy of the stratigraphic interpretation of the seismic records, to investigate reflective horizons identified from seismic records and to collect dateable material. Interpretation of the sediment cores reveals that a proto Lake Sibaya existed on drowned dune topography, during the period ± 43500 BP to ± 25500 BP prior to the Last Glacial Maximum. During the early to mid Holocene the Lake Sibaya site was occupied by a saline lagoon which underwent isolation from the sea ± 5030 BP. Since the mid-Holocene the lake has evolved to totally freshwater conditions and has undergone little sedimentation. The geological evolution of the Lake Sibaya area is discussed in terms of the geometry of the identified seismic sequences, the sedimentary characteristics of these sequences and the radiocarbon dates provided from the sediment cores. Palaeo-environmental conditions during the accumulation of the sedimentary sequences is discussed where fossil remains permit. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

This study integrates sequence stratigraphy of the Late Permian Toolachee Formation in the non-marine intracratonic Permian-Triassic Cooper Basin, Australia with 3-D seismic attribute analysis to predict the extent of depositional environments identified on wireline and well core data. The low resolution seismic data (tuning thickness 23 - 31 m) comprised of six seismic horizons allowed the successful testing of sequence stratigraphic interpretations of the productive Toolachee Formation that were based on wireline data. The analysis of 29 well logs and three 20 m core intervals resulted in the identification of eleven parasequences that comprise the building blocks of an overall transitional systems tract, characterised by a gradual increase in accommodation. The parasequences reflect cyclic transitions between braided and meandering fluvial systems as a result of fluctuations in sediment flux, possibly driven by Milankovitch climatic-forcing. The seismic horizon attribute maps image mostly the meandering fluvial bodies within the upper parts of the parasequences, but some maps image the lower amalgamated sand sheets and show no channel structures. Categorisation of the fluvial bodies in the overbank successions reflects a gradual decrease in sinuosity, channel width, and channel belt width up-section, supporting the overall increase in accommodation up-section. Similar acoustic impedance values for shales and sands do not suggest successful seismic forward modelling between the two lithologies. Geological interpretations suggest most imaged channel fill to be made up predominantly of fine sediments, as channel avulsion and abandonment is common and increases with time. Seismic forward modelling resulted in the interpretation of carbonaceous shale as a possible channel fill, supporting the geological interpretations. The three major identified fluvial styles; braided, meanders, and distributaries are potential targets for future exploration. Extensive sand sheets deposited from braided fluvial systems require structural traps for closure. Meandering and anastomosing channel systems represent excellent stratigraphic traps, such as the basal sands/gravels of laterally accreted point bars.

The use of seismic methods in hard rock environments in Western Australia for mineral exploration is a new and burgeoning technology. Traditionally, mineral exploration has relied upon potential field methods and surface prospecting to reveal shallow targets for economic exploitation. These methods have been and will continue to be effective but lack lateral and depth resolution needed to image deeper mineral deposits for targeted mining. With global need for minerals, and gold in particular, increasing in demand, and with shallower targets harder to find, new methods to uncover deeper mineral reserves are needed. Seismic reflection imaging, hard rock borehole data analysis, seismic inversion and seismic attribute analysis all give the spatial and volumetric exploration techniques the mineral industry can use to reveal high value deeper mineral targets. / In 2002, two high resolution seismic lines, the East Victory and Intrepid, were acquired along with sonic logging, to assess the feasibility of seismic imaging and rock characterisation at the St. Ives gold camp in Western Australia. An innovative research project was undertaken combining seismic processing, rock characterization, reflection calibration, seismic inversion and seismic attribute analysis to show that volumetric predictions of rock type and gold-content may be viable in hard rock environments. Accurate seismic imaging and reflection identification proved to be challenging but achievable task in the all-out hard rock environment of the Yilgarn craton. Accurate results were confounded by crocked seismic line acquisition, low signal-to-noise ratio, regolith distortions, small elastic property variations in the rock, and a limited volume of sonic logging. Each of these challenges, however, did have a systematic solution which allowed for accurate results to be achieved. / Seismic imaging was successfully completed on both the East Victory and Intrepid data sets revealing complex structures in the Earth as shallow as 100 metres to as deep as 3000 metres. The successful imaging required homogenization of the regolith to eliminate regolith travel-time distortions and accurate constant velocity analysis for reflection focusing using migration. Verification of the high amplitude reflections within each image was achieved through integration of surface geological and underground mine data as well as calibration with log derived synthetic seismograms. The most accurate imaging results were ultimately achieved on the East Victory line which had good signal-to-noise ratio and close-to-straight data acquisition direction compared to the more crooked Intrepid seismic line. / The sonic logs from both the East Victory and Intrepid seismic lines were comprehensively analysed by re-sampling and separating the data based on rock type, structure type, alteration type, and Au assay. Cross plotting of the log data revealed statistically accurate separation between harder and softer rocks, as well as sheared and un-sheared rock, were possible based solely on compressional-wave, shear-wave, density, acoustic and elastic impedance. These results were used successfully to derive empirical relationships between seismic attributes and geology. Calibrations of the logs and seismic data provided proof that reflections, especially high-amplitude reflections, correlated well with certain rock properties as expected from the sonic data, including high gold content sheared zones. The correlation value, however, varied with signal-to-noise ratio and crookedness of the seismic line. Subsequent numerical modelling confirmed that separating soft from hard rocks can be based on both general reflectivity pattern and impedance contrasts. / Indeed impedance inversions on the calibrated seismic and sonic data produced reliable volumetric separations between harder rocks (basalt and dolerite) and softer rock (intermediate intrusive, mafic, and volcaniclastic). Acoustic impedance inversions produced the most statistically valid volumetric predictions with the simultaneous use of acoustic and elastic inversions producing stable separation of softer and harder rocks zones. Similarly, Lambda-Mu-Rho inversions showed good separations between softer and harder rock zones. With high gold content rock associated more with “softer” hard rocks and sheared zones, these volumetric inversion provide valuable information for targeted mining. The geostatistical method applied to attribute analysis, however, was highly ambiguous due to low correlations and thus produced overly generalized predictions. Overall reliability of the seismic inversion results were based on quality and quantity of sonic data leaving the East Victory data set, again with superior results as compared to the Intrepid data set. / In general, detailed processing and analysis of the 2D seismic data and the study of the relationship between the recorded wave-field and rock properties measured from borehole logs, core samples and open cut mining, revealed that positive correlations can be developed between the two. The results of rigorous research show that rock characterization using seismic methodology will greatly benefit the mineral industry.