2013 IEEE/OES Acoustics in Underwater Geosciences Symposium最新文献

{"title":"Seismic echo-characters and sedimentary distribution on the South Shetland Islands continental margin, Antarctica","authors":"F. Magrani, Arthur Ayres Neto","doi":"10.1109/RIOACOUSTICS.2013.6684010","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684010","url":null,"abstract":"The present work consists in characterizing the sedimentary distribution on the South Shetland Islands continental margin, Antarctica Peninsula, through the interpretation and correlation of high-resolution seismic profiles and geological samples. The characterization was made through echo-characters, maps of seismic amplitudes and its correlation with the collected samples, filling the gap in scientific research about echo-characters at this location. Five different echo types have been identified and classified. Echo types I and II have good seismic resolution and are characterized by continuous sharp bottom echoes with sub-parallel reflections. Echoes III and IV are characterized by difuse and very prolonged bottom echoes with no sub-bottom reflectors. Echo V is associated to glacial deposits on the upper slope in response to deglaciation and the transport of coarse grains in a muddy matrix and is characterized by diffraction hyperbolae. The echo-characters showed good correlation with geological samples collected along the Bransfield Strait and bays of the King George Island, but not completely with the amplitudes map. Echo I has medium-high amplitudes and the samples within its area of occurrence (AM-02 and AM-14) indicates silty sand and sandy silt, respectively. Echo II presents the lowest seismic amplitudes and the sample within its area (AM-17) shows a content of approximately 90% mud. Echos III and IV, located on the shallowest portions of South Shetland's continental margin, demonstrate medium-low amplitude values, and are related to samples AM-01 and AM-04, both classified as sandy-silt with approximately 35% of sand.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"1111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122925151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research on acoustic vector properties in shallow water for geoacoustic parameters inversion","authors":"Han-hao Zhu, S. Piao, W. Liu, Haigang Zhang","doi":"10.1109/RIOACOUSTICS.2013.6684013","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684013","url":null,"abstract":"This paper focuses on using the acoustic vector field physical properties for ocean bottom geoacoustic inversion. The vector acoustic field characteristics of a shallow water waveguide with elastic bottom are described according to the Fast Field Models (FFM) at first. The intensity and propagation direction of power fluxes I in underwater acoustic field is numerically investigated, and the correlation of sound pressure and particle velocity is analyzed. For the vertical velocity contains more information from bottom, a sensitivity test for the vertical component of the correlation coefficient to geoacoustic parameters is presented and the benefit brought to better resolve the coupling effect of the two parameters are also discussed in this paper.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126649945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seabed features characterization of Barra Norte by multibeam survey: Furrows evidence at the outermost river branch of the Amazon River","authors":"F. M. Pinheiro, S. Vinzón","doi":"10.1109/RIOACOUSTICS.2013.6683978","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6683978","url":null,"abstract":"Barra Norte is a highly energetic environment that constitutes the main navigational route between Atlantic Ocean and the world's major fluvial system, the Amazon. The recent geomorphology of the actual navigational channel was investigated by a multibeam system installed at the Brazilian navy's hydro-oceanographic vessel Garnier Sampaio (H-37). These data were collected between September and October of 2011 resulting in the survey of a corridor of 150m × 62km long at Curua Channel (close to highly dynamic sand banks, referred as area A) and 50m × 57km at an outer region of the Amazon River inner continental shelf, where fluid mud accumulate (area B). Data processing was realized at Caris HIPS and SIPS considering water level obtained from a calibrated hydrodynamic model, based on Environmental Fluids Dynamical Code, to account for spatial tidal variability. Bathymetry, gradient and backscatter maps were created with 1 meter resolution. The seafloor showed constantly decreasing depths from area A to B (SW-NE), resulting in a 1:6500 gradient, where major changes were locally associated to bedforms. Five seabed types were identified according to bedform occurrence: (1) predominantly flat; (2) transition (any two or more types); (3) small to large dunes; (4) furrows; and (5) mega dunes. Types 2, 3 and 4 showed nonuniform distribution, occurring mainly at Curua Channel. Ebboriented mega-dunes occurred at the extreme SW of the transect, the deepest surveyed area, close to the most restricted transverse section, indicating strong NE residual currents. Furrows where observed just at area A, being closer to sandy seafloor than to the fluid mud banks of area B. They are slightly aligned to the main currents direction and their high backscatter intensity indicates the presence of a more consolidated sediment, possibly a mixture of sand and cohesive sediments, what makes them slightly irregular in plan. According to furrows classification they can be described as type 1C, being of variable shape and very steep walls, reaching 30°. Type 1C furrows develop under directionally stable flows where sedimentation and erosion balances each other, what can be supported by its spatial distribution, close to significant sand banks or at bathymetric depressions of Curua Channel. At area B, after a small segment of small dunes and high backscatter at its extreme SW, a slowly increasing weak signal was observed from longitude 49.5W on. It covered about 85% of the surveyed area B and is related to Amazon River fine sediments that tend to deposit as fluid mud at the inner continental shelf. Sediment samples corroborate these findings.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131918787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Passive localization techniques of a vector hydrophone based on time-reversal method","authors":"Yu Chen, Shuqing Ma, Liufang Fu, Z. Meng","doi":"10.1109/RIOACOUSTICS.2013.6684004","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684004","url":null,"abstract":"The pressure and horizontal velocity signals of a vector hydrophone are adopted together in the time-reversal (TR) processing, which can be used in the passive localization of the underwater target. In order to model the replica field, an improved cost function of the Bartlett estimator is offered. Based on the single floor seabed model, the sensitivities of the geoacoustic parameters are analyzed. It was found that, the bottom density and bottom attenuation are insensitive to the proposed Bartlett estimator, and the sound speed of the seabed and depth of the ocean are sensitive parameters. Further, the performance of TR localization shows robustness to the mismatch of the insensitive parameters. Hence, only the sensitive parameters need to be calculated in the geoacoustic inversion. In order to demonstrate the proposed geoacoustic inversion method and the passive TR localization technology, an experiment of a vector hydrophone was carried out in the lake. Using the optimized parameters obtained from the inversion, the passive TR localization of the target was successfully realized.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"163 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133845551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multi-sensor approach for remotely modeling and mapping sediment properties","authors":"K. Siemes, J. Hermand, M. Snellen, D. Simons","doi":"10.1109/RIOACOUSTICS.2013.6684018","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684018","url":null,"abstract":"Detailed information about the oceanic environment is essential for many applications in the field of marine geology, marine biology, coastal engineering, and marine operations. Especially, knowledge of the sediment properties is often required. Acoustic remote sensing techniques have become highly attractive for classifying the sea bottom and mapping the distribution of sediment properties, due to their high coverage capabilities and low costs compared to common sampling methods. In 2007, the Maritime Rapid Environmental Assessment / Blue Planet trial (MREA/BP'07) was carried out in a shallow water environment with fine-grained sediments in the Mediterranean Sea, in order to investigate means of efficiently obtaining a detailed picture of the underwater environment [1]. Measurements were taken by a large set of sensors, including echosounders, seismic systems, and dedicated array configurations, thereby providing all information required to fully describe the environment. Since these systems operate at different frequencies, they provide information on the sea bottom at different depths. This gave reason for a combination of the acoustic data as taken by the different sensors. Especially, the combination of the classification of the upper sediment layer achieved by the hydrographic surveying and the sediment layering obtained from the seismic systems resulted in a well-described three-dimensional picture of the distribution of the underwater sediments [2]. In this paper we present this environmental picture in the context of geoacoustic inversion. Geoacoustic inversion techniques are an attractive means for estimating a variety of physical properties of underwater environments, such as sound speed, density, and attenuation in each sediment layer, as well as layer thicknesses. Geoacoustic inversion, however, comes at the price of high computational efforts. Especially, in cases in which large numbers of parameters need to be inverted for, finding those parameters that provide the best fit between the measurements and model predictions requires hundreds of iterations. Efficient global optimization tools can reduce these efforts. We propose that both the surveying and inversion efforts can be reduced further by carrying out geoacoustic inversion at a small number of selected sites, only. In this paper it is investigated whether a combination of hydrographic and seismic surveying is suitable for selecting areas for sub-seafloor sediment classification by geoacoustic inversion techniques.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132555295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Attenuation of underwater sound through stationary arrays of large tethered encapsulated bubbles","authors":"Kevin M. Lee, P. Wilson, M. Wochner","doi":"10.1109/RIOACOUSTICS.2013.6684002","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684002","url":null,"abstract":"The ultimate goal of this work was to accurately predict attenuation from large tethered encapsulated bubbles used in an underwater noise abatement system. Measurements of underwater sound attenuation were obtained during a set of lake experiments, where a low-frequency sound source was surrounded by different arrays of encapsulated bubbles with various individual bubbles sizes and void fractions, and compared with an existing predictive model by Church [J. Acoust. Soc. Am. vol. 7, 1510-521 (1995)] for the dispersion relation in liquid containing encapsulated bubbles. Although Church's model was originally intended to describe ultrasound contrast agents, it was evaluated here for large bubbles (on the order of 10 cm) and fairly good quantitative agreement between the data and the model was observed. A modification of Church's model was made by combining it with Kargl's model [J. Acoust. Soc. Am. vol. 111, 168-173 (2002)], attempting to incorporate multiple scattering effects, which may be important at high void fractions. However, a comparison with the data indicates that the Church-Kargl hybrid as implemented here may overcompensate for these effects. These results indicate that Church's model is sufficient for use as a design tool for tethered encapsulated bubble screens with void fractions less than 2%.","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134008252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acoustical database dedicated to fish stock assessment being optimized to generate seafloor information and integrate biological, environmental and geomorphological studies","authors":"L. Madureira, M. Pinho, P. L. Costa, S. Weigert, G. Griep, L. Calliari","doi":"10.1109/RIOACOUSTICS.2013.6684024","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684024","url":null,"abstract":"The Fisheries Technology and Hydroacoustics Laboratory (TECPESQ-Institute of Oceanography, University of Rio Grande-IO-FURG-Brazil) has traditionally dedicated its working group to fish stock assessments using hydroacoustics. This technique allows the remote detection of organisms throughout the transmission of acoustic energy and the evaluation of the echoes. In order to attend different projects, we have prospected the Brazilian coast on board the R.V. AtlanticoSul, along more than 47,000 nautical miles. Acoustic data have been collected with scientific echo sounders SIMRAD EK 500 or SIMRAD EK 60. Complementary data have also been obtained, sampling organisms in the water column and bottom, as well as gathering environmental data. The large acoustic database was, at a certain moment, in contrast with the shortage of bathymetric and geomorphological data available, to be incorporated in the biological and environmental studies. This situation forced the group to start filtering and validating bathymetric and Bottom Surface Backscattering Strength (BSBS) data, collected along all cruises but not used previously and considered as secondary information. In 2004, part of the BSBS data base were analyzed and correlated to substrate composition and particle size which allowed to refine and detail the overall characteristics of the of the Southeast and South sectors of the Brazilian continental shelf and shelf break. In the same year, acoustic seafloor data were used to map three pockmarks, at a depth of 700 m, in the Santos Basin. In 2005, bathymetric data from seven surveys were integrated with satellite altimetry to generate three-dimensional maps of the Brazilian continental margin, which allowed a more detailed analysis of geological features, such as the Cone and the Plato do Rio Grande, Plato de Sao Paulo and the Vitoria Trindade Chain. In 2007, distinct seabed features were identified and entered in a GIS after the analysis of data collected in the Brazilian continental margin. In 2009, data from four cruises on the southern most part of the continental shelf were used to map the Albardao paleochannel, a vestige of ancient drainage of the La Plata River. BSBS values inside of this channel were significantly lower than from the external surrounding area, indicative of the presence of muddy sediments. In 2011, BSBS data were entered in a 3D GIS and integrated to bathymetric, environmental and sedimentological data, which allowed the identification of areas with acoustic features typical of phosphorite deposits, a mineral of great strategic and economical importance. Recently, in 2013, a map of the bottom reflectivity of the Pelotas Basin was finished, generated from 1,507,823 BSBS values, which allowed the identification of four important sea bottom features. The TECPESQ acoustic database increases at every research cruise. The ship is now fitted with new transducers, increasing the number of frequencies which will lead to more detailed studies o","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114866612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the acoustic detection of flint blade in soft sediment","authors":"Rostand Tayong Boumda, J. Hermand","doi":"10.1109/RIOACOUSTICS.2013.6684001","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684001","url":null,"abstract":"A lot of Stone Age sites are known to be destroyed by the wave activity of risen and fallen sea level. A direct consequence of this destruction is a loss of environmental information about the relation of human culture and the changing environment. Even when this destruction occurs, there is still some remains of prehistoric landscapes which can provide useful information. With the relatively complex seawater environment, the use of acoustic methods to detect and map submerged Stone Age sites is of great importance for archaeological research. This paper presents a preliminary numerical study for the geoacoustic characterization of Stone Age cultural layers containing worked flints and blades in particular. Finite element modeling tools are used to investigate the feasibility of detecting acoustically a submerged flint. Since well preserved submerged settlement remains will often be related to areas with soft sediments, the acoustic response of a flint buried in soft sediment is here simulated. In classical environments, flints are also known to be submerged in a cultural layer surrounded by seawater, sand, mud and a substrate layer of Moraine. A theoretical calculation of flint resonance frequencies shows that depending on their characteristics, they can produce a wide range of frequencies beyond 2 kHz as it has been observed experimentally. In this study, a Ricker wavelet source is used to estimate the total and scattered pressure fields due to a flint blade sample. To detect the submerged flint, the source contains the determined fundamental resonance obtained at 10.6 kHz. Snapshots for different views around the flint are analyzed to detect the effect of the flint sample. In the frequency domain, it is observed a relatively detectable zone around the flint. The total pressure level is computed at a fixed distance of 5 cm above the flint blade buried inside 5 cm of a cultural layer environment. A sharp peak is noticed to appear for this latter result at the given resonance of about 18% the emitting signal for the flint. In this preliminary study, the case of the flint buried inside 15 cm of cultural layer overlying 100 cm of sand is also computed and presented. In the time domain, the total pressure fields at the indicated fixed distance for both cases with and without the flint blade are compared in the case of an environment composed of 15 cm of cultural layer overlying 100 cm of sand layer. The result shows that although the sound pressure response amplitude is slightly increased for the case with the flint blade sample, the difference between these responses is about 10% of the incidence source amplitude. This first step modeling suggests a possibility to use an acoustic method to detect and localize worked flints buried inside soft sediment environment. The other results obtained are analyzed and discussed. The study support the development of a geoacoustic inverse method to characterize submerged flints cores and blades but also the accu","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"186 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124751931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sonar for engineering","authors":"I. Florence, J. H. Kristensen, C. Wallace","doi":"10.1109/RIOACOUSTICS.2013.6683983","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6683983","url":null,"abstract":"The history of this Project can trace its roots back to 2004 when Hurricane Ivan's 165mph winds caused damage to various oil pipelines and offshore structures in the Gulf of Mexico. In later years, after Rita and Katrina hit the area, we truly started to see the detrimental effects of hurricanes to the offshore oil and gas industry. The effects highlighted the need for proactive risk assessments. Hurricane Katrina itself damaged 113 offshore oil and gas platforms and 457 oil and gas pipelines, encompassing many thousands of miles. Reports were anything from completely destroyed platforms to dented pipes or in some cases completely fractured. Many of these destroyed platforms resulted in either gas or oil leaks for several weeks before the wells could be successfully blanked. In order to close the well the engineers will first need to assess the damage caused by the hurricane. If a platform jacket has collapsed is it obscuring the well head? Or has perhaps the debris damaged a pipeline further down?","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122470959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Some limitations of shallow water geophysical devices imposed by different oceanographic and geological conditions","authors":"C. A. Felix, Thiago S. Martins, C. H. C. Soares, Vanessa Guesser, Larissa F. Demarco, B. Suthard, R. Barletta, Jorge Souza, M. M. de Mahiques","doi":"10.1109/RIOACOUSTICS.2013.6684000","DOIUrl":"https://doi.org/10.1109/RIOACOUSTICS.2013.6684000","url":null,"abstract":"Applied shallow water seismic-reflection methods are an important component in designing engineering projects to address navigability, port construction and dredging activities, among others. The more these techniques are applied, the more that is known about the environment in question resulting in an increased potential to minimize costs. It is crucial to choose the correct techniques to get the desired responses, since each device has its own frequencies and operational requirements. When site-specific physical parameters and characteristics are taken into consideration when planning survey operations, high quality data can be acquired. However, this study presents some limitations of shallow water geophysical devices imposed by different oceanographic and geological conditions. Examples of a Side Scan Sonar and sub-bottom profilers were taken from four (4) survey sites along the Brazilian territory: (1) a ria-like coastal environment along the southern coast of Rio de Janeiro State; (2) the coast of Bahia State; (3) a rocky river in the central region of the country; and (4) a macro tide-dominated estuary in the Northeast. The equipment was selected and operated with specific project goals in mind including: definition of stratigraphy, depth to crystalline basement, and sediment thickness. The first site is an example of classic shallow sub-seafloor gas occurrences off the coast of Rio de Janeiro, where those gas accumulations were mapped with an integrated system consisting of a boomer (0.5 - 2.0), chirp (2.0 - 8.0) and a pinger (24 kHz), with the seismic signal being limited by strong reflections that caused phase inversions. In a similar situation, a boomer survey was conducted off the coast of Bahia State to define the depth of consolidated rock, although the signal penetration was limited by a layer of soft sediments. This layer was sampled with percussion cores and revealed very soft clay content that the cores easily penetrated. This layer also caused phase inversion in the seismic data, not very common in sediments without gas accumulations. The third site is a narrow river in which the boomer source was employed. The presence of solid rock, plus the characteristics of this impulsive source, resulted in a strong sideswipe effect, which can cause some confusion in the interpretation process. The last site is known to have high current speeds due to the tidal amplitude. The estuary was surveyed with a Side Scan Sonar operating with dual, simultaneous frequencies of 300 and 600 kHz. The high frequency swath was dispersed and attenuated within in the water column in a way that the signal could not reach the bottom, thus resulting in no acquisition at all. The 300 kHz was used without any issue; water samples (Niskin Bottle) were taken which demonstrated a high concentration of particulate material on the water column. Along with the Side Scan, a chirp survey was conducted operating in a frequency range of 0.5 - 8.0 kHz. The chirp signal p","PeriodicalId":245877,"journal":{"name":"2013 IEEE/OES Acoustics in Underwater Geosciences Symposium","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131717350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}