An approach to detect and image multiple damages in a platelike structure is presented. A structural health monitoring system (SHMS) with a linear array of actuators/sensors is proposed. The integrated actuators/sensors are used to activate/receive lowest-order antisymmetric A0 mode Lamb waves. A migration technique used in geophysical exploration and seismic prospecting is adopted to interpret...

Prestack migration methods based on data binning produce kinematic artifacts, i.e. coherent events not corresponding to actual reflectors, in the prestack image volume, when the medium is strongly refracting. Shot-geophone (“survey sinking”) migration, on the other hand, does not produce such artifacts when events to be migrated arrive in the data along non-turning rays. In contrast to prestack...

Poststack MD has been shown to be an effective method for attenuating migration noise, improving lateral resolution, and correcting for some migration amplitude distortion in 2-D and 3-D data (Hu and Schuster, 1998; and Hu and Valasek, 1999). In field data tests, poststack MD has successfully improved the 3-D poststack migration images (Hu and Valsek, 1999) obtained from both synthetic and fiel...

Velocity continuation is an imaginary continuous process of seismic image transformation in the postmigration domain. It generalizes the concepts of residual and cascaded migrations. Understanding the laws of velocity continuation is crucially important for a successful application of time-migration velocity analysis. These laws predict the changes in the geometry and intensity of reflection ev...

We show in this paper how the application of convex duality leads to various reformulations of the classical non optimizable least squares approach to waveform prestack inversion. These reformulations search all for i) a background velocity model and ii) a re-ectivity model deened in the time domain, and linked to the usual depth reeectivity model by prestack depth migration. We show that the d...

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...

Recent analysis and synthetic examples have shown that many prestack depth migration methods produce non-flat image gathers containing spurious events, even when provided with a kinematically correct migration velocity field, if this velocity field is highly refractive. This pathology occurs in all migration methods which produce partial images as independent migrations of data bins. Shot-geoph...

Reliable seismic depth migrations require an accurate input velocity model. Inaccurate velocity estimates will distort point diffractors into smiles or frowns on a depth section. For both poststack and prestack migrated sections, high velocities cause deep smiles while low velocities cause shallow frowns on migrated gathers. However, for prestack images in the offset domain, high velocities cau...

Seismic imaging based on single-scattering approximation is based on analysis of the match between the source and receiver wavefields at every image location. Wavefields at depth are functions of space and time and are reconstructed from surface data either by integral methods (Kirchhoff migration) or by differential methods (reverse-time or wavefield extrapolation migration). Different methods...

We present a simple method for computing angle-domain Common Image Gathers (CIGs) using prestack reverse time migration. The proposed method is an extension of the method proposed by Rickett and Sava (2001) to compute CIGs by downward-continuation shot-profile migration. We demonstrate with a synthetic example the use of the CIG gathers for migration velocity updating. A challenge for imaging b...