ZTK Kirchhoff PSTM & PSDM

Kirchhoff methods are widely recognized as one of the most comprehensive and flexible methods of imaging prestack 3-D seismic data. ZTK is Z-Terra’s implementation of three-dimensional Kirchhoff migration in depth and in time. ZTK images seismic data by approximately solving the wave equation with a boundary integral method. The acoustic reflectivity at every subsurface image point is computed by summing the recorded data on multidimensional surfaces; the shape of the summation surfaces and the summation weights are computed from Green’s functions of the single scattering wave propagation experiment. Though the theory behind 3-D Kirchhoff migration is quite straightforward, an efficient implementation of the algorithm poses many challenges, such as input data distribution among the computational units of a distributed system, optimization of network traffic and local data I/O, management of the processing nodes, the ability to add and subtract nodes during runtime, check-pointing, memory management, choice of anti-aliasing method, travel-time interpolation issues, and the effects of aperture and data acquisition geometry on efficiency. ZTK includes many integration features that enable the user to quickly set up and QC the job: a base map viewer, grid definition and input data geometry controls, a SEG Y viewer for the input data and trace header information, topography specification for land and OBC data, and 2-D and 3-D viewers for the velocity model, travel times, stacks, and gathers.