The most difficult and unwanted image is the non-migrated image - and the step "Migration" in the processing is the most sophisticated part, Migration can be simply described as "migrating" reflection events to their correct position in the subsurface, the non-migrated position results from the assumption that transmitted ray is equal to the reflected ray at any point in the subsurface , which is not the case if you have dipping reflectors or faults.

Different algorithms have been developed in the last four or five decades to correct for this , each is trying to reach the most accurate possible image, and most algorithms are dependent on interval and average velocities in the subsuraface so it requires very accurate and high density velocity picking from the pre-stack. you can go and do more research on that , its a very interresting topic, other processing aspects are of the same importance but not sophisticated as Migration.

Geophysical signal processing is an important field that deals with the analysis, interpretation, and modeling of various geophysical data, such as seismic, gravity, magnetic, and electromagnetic data. The application of signal processing techniques in geophysics has led to significant advances in various areas, such as earthquake detection and location, imaging of subsurface structures, and exploration of natural resources, among others.

Some of the problems that can be solved in the field of geophysical signal processing are:

Current research in geophysical signal processing is focused on developing advanced signal processing techniques that can handle large and complex geophysical datasets. Machine learning techniques, such as deep learning and neural networks, are being used to develop automatic signal processing algorithms that can improve the efficiency and accuracy of geophysical data processing. Other research areas include the development of 4D imaging techniques that can monitor changes in subsurface structures over time and the development of joint inversion techniques that can combine multiple geophysical datasets for improved imaging of subsurface structures.