In this paper we define the theory and basic principles to move (redatum) the surface shots from a walk away VSP to be as if they had been located in the borehole. We will refer to this theory using several of the terms used in the literature including Time Reverse Acoustics (TRA), Seismic Interferometry (SI) and Virtual Source (VS) technology. Regardless of the name, the theory is built upon r...

Measuring reflection amplitude versus offset (AVO) has proved to be effective in reservoir characterization. Experience shows that AVO inversion methods based on amplitude-preserved prestack migration typically provides a more accurate lithology estimate than NMO-based AVO analysis. However, some artifacts may be introduced into the migration section due to an undersampled acquisition geometry,...

In this paper, I apply the migration deconvolution to synthetic seismic images that have been distorted by cable feathering, migration velocity errors and recording geometry variations. The results show that migration deconvolution is able to suppress the velocity and geometry errors and can noticeably improve the quality of the migration image for both 2-D poststack and 3-D prestack migration....

Aims: To provide baseline data regarding GPs’ knowledge, experience, and attitudes toward the management of PsychoStimulant Drug Misuse (PSDM) patients to inform future education and training initiatives. Methods: A structured cross-sectional postal questionnaire was developed following initial content setting interviews, piloted then sent to a sample of 250 GPs in north east Scotland. Findings...

A frequency domain tomographic inversion was developed to estimate frequency dependent energy attenuation by using prestack depth migration common image gathers (CIGs). The frequency dependent attenuation is estimated from the centroid frequency difference for reflections in CIGs. Migration stretch and ghost effects are taken into account to get correct measurements of frequency. This method ma...

Abstract We developed a modified topography prestack time migration (PSTM) scheme that can improve the imaging resolution by applying effective Q to migration. The computation of traveltime at each location in is based on floating datum smoothed rugged topography. Unlike common quality factor Q, only determines frequency-dependent amplitude and single location, which enables us establish model ...

In order to produce an accurate depth migration of a seismic line, one needs an accurate velocity model. This model should reflect the lithology and lithostatic load that the rocks have experienced through burial and deformation. If we understand the geometry of these rocks, and their behaviour upon deformation, we can produce a more accurate velocity model. Performing palinspastic restoration ...

The optimal checkpointing algorithm (Griewank and Walther, 2000) minimizes the computational complexity of the adjoint state method. Applied to reverse time migration, optimal checkpointing eliminates (or at least drastically reduces) the need for disk i/o, which is quite extensive in more straightforward implementations. This paper describes optimal checkpointing in a form which applies both t...