An absorbing-layer method of 3-D seismic migration in an irregular acquisition geometry

3-D seismic migration for an irregular acquistion geometry usually needs zero-trace padding to form a regular geometry. The benefit of zero padding is easy to do 3-D migration, but it will reduce the computative efficiency and migrated quality. In this paper we use an additional absorbing thin layer surrounding the irregular geometry instead of zero padding. It has greatly decreases computative cost and improves the migrated seismic data quality. In order to form an absorbing layer, a damping factor is added to one-way wave equation. Since the wave-field attenuates quickly when the wave penetrates this thin layer, the reflection is very small when the wave-field at the outer boundary of the absorbing layer is taken as zero, Since the migration program with the zero-boundary condition is easy to be implemented, 3-D migration of seismic data for a irregular acquisition geometry can be done directly. The effectivity of this method is illustrated by processing the practical data.