The recession in the oil industry, and in particular the exploration fields, has not deterred the industry from continued research into the improvement of its geophysical techniques. Latterly, there has been much emphasis on the interpretation of data, and on optimizing data processing systems. The new book series Advances in Exploration Geophysics will reflect the trends in both these areas as well as the new and important aspects of established subjects such as data acquisition, etc. The series will be edited by Professor Berkhout, who is also author of this first volume. In the last few years the role of wave theory in seismic processing has increased significantly; new wave theory solutions to old problems have been formulated with impressive success. In the near future the technology of seismic processing will be largely based on wave theory. This means that, in the coming years, emphasis will further shift from time series based techniques to wave theory based techniques. As a consequence, it is imperative that geophysicists have a thorough understanding of seismic wave theory in order to cope with the technology of tomorrow.