In this paper, with the use of Larmor clock, the tunneling times of one-dimensional combined potential are calculated. According to the results, the characters of Larmor times which are defined by Larmor clock method are discussed. It was found that the equality τyT=τyR=τD does not hold in general. Whether the equality τyT=τyR holds is determined by the symmetry of the potential. The Larmor times τyT and τyR may offer definition for transmitted time τT and reflected time τR, but τxT,τxR,τyT and τyR cannot. In addition, τyT and τyR can satisfy the equality τD=TτyT+RτyR.

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Complex geology and deepwater presalt targets offshore Brazil lend themselves to seismic imaging challenges. The postsalt sections of the Santos and Campos Basins also featured thin-bed, high-impedance layers of volcanic material and other shallow velocity anomalies. These features were often near the top of salt (TOS) and produced areas of poor presalt focusing. Because accurately modeling the postsalt was imperative for imaging the presalt, we developed a new workflow for velocity model updating. Where previous top-down methods have failed, our method embraced the challenges of imaging beneath the volcanics by incorporating additional presalt information into the updates. Our method is interpretation-dependent but provides a robust and reliable workflow for updating the postsalt velocity model in the presence of complex geology. Using a narrow azimuth data set acquired with variable-depth streamers, we evaluated the effectiveness of our iterative workflow. The result was improved presalt imaging. IntroductionNumerous seismic imaging challenges exist in the basins offshore Brazil, mostly due to the region's complex geology and deepwater presalt targets. The postsalt sections of the Santos and Campos Basins also feature thin-bed, high-impedance layers of volcanic material and other shallow velocity anomalies. These features can produce areas of poor focusing beneath them due to the complex lateral velocity variation related to the movement of the volcanic layers. Because accurately modeling the postsalt is imperative for imaging the presalt, which is today's focus of exploration in the region, we present a new workflow for velocity model updating. Our method builds on the work of others and incorporates different methods into an iterative and holistic approach to velocity model building.

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