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The processing of multicomponent seismic data is already a challenge concerning the velocity analysis. When it is performed for offshore survey, the difficulty increases a lot more with the use of OBN (Ocean Bottom Nodes) technology. The ray tracing asymmetry generated by the wave conversion and the difference of datum between source and receptor are not the only factors which contribute for a strongly nonhyperbolic travel-time event. The layered subsurface models and the large offsets employed in the offshore surveys make the nonhyperbolicity even stronger. Aiming to solve this problem, eight approximations to perform the velocity analysis were tested for two models. The complexity analysis of each nonhyperbolic multiparametric approximation was also studied to understand their behaviors during the optimization process. The relative error between the observed curve and the calculated curve with each approximation was computed for PP and PS reflection events of two models. With these informations, it was possible to determine which approximation is the most reliable one for this kind of models. Keywords: multicomponent, OBN, nonhyperbolic, multiparametric. Resumo O processamento de dados sismicos multicomponentes ja e um desafio com relacao a analise de velocidades. Quando realizado para levantamentos maritimos, a dificuldade aumenta muito mais com o uso da tecnologia OBN (Ocean Bottom Nodes). A assimetria no tracado de raios gerada pela conversao de onda e pela diferenca de profundidade entre fonte e receptor nao sao os unicos fatores que contribuem para um evento de tempos de trânsito fortemente nao-hiperbolico. Os modelos estratificados de subsuperficie e os grandes afastamentos aplicados nos levantamentos maritimos tornam a nao-hiperbolicidade ainda mais forte. Visando resolver este problema, oito aproximacoes para realizar a analise de velocidades foram testadas para dois modelos. A analise de complexidade de cada aproximacao nao-hiperbolica multiparametrica tambem foi estudada para entender seus comportamentos durante o processo de otimizacao. Os erros relativos entre as curvas observadas e calculadas com cada aproximacao foram calculados para os eventos de reflexao PP e PS dos dois modelos. Com estas informacoes, foi possivel determinar qual aproximacao e a mais confiavel para estes tipos de modelos. Palavras-chave: multicomponente, OBN; nao-hiperbolico, multiparametrico.

brazilian journal of geophysics

Comparative analysis of nonhyperbolic multiparametric travel-time approximations of multicomponent seismic data considering difference of depth between source and receiver using OBN technology