Without exception, primaries are the only events that are ever migrated. Arranging for a more complete set of primaries will enhance imaging. The approximate image of an unrecorded primary can be realized by isolating and migrating a subevent primary of a multiple. A more complete set of images from recorded primaries and approximate images of unre­corded primaries, can enhance imaging.

We will show that if one could migrate with an accurate discontinuous velocity model, then for data consisting of primaries and multiples, that multiples will never contribute to ( i.e., they will neither help nor harm) the migrated result.  And when migrating with a smooth velocity model, that every single multiple will cause a false and misleading, injurious image in the migration.   Since our velocity models, in practice, are smooth , multiples must be removed before imaging. We will explicitly demonstrate that methods that use a multiple to extract an approximate image of an unrecorded primary, while they can be useful( and we will show positive examples) , are not migrating the multiple, and that this is a substantive, significant matter and not a question of quibbling or semantics. Also, care must be taken for creating inevita­ble false events ( called cross talk) in these methods  that provide approximate images of unrecorded primaries.

We will present a brief discussion on the recent advances and progress, and the very serious high priority open issues and pressing challenges in  multiple removal.

Dr. Arthur B. Weglein holds the Hugh Roy and Lillie Cranz Cullen Distinguished University Chair in Physics at the University of Houston. He is a professor in the Department of Physics and the Department of Earth and Atmospheric Sciences. Weglein is the Director of the Mission-Oriented Seismic Research Program, a research consortium supported by the major oil and service companies in the world. Dr. Weglein served as the SEG Distinguished Lecturer in 2003, and was awarded the SEG’s Reginald Fessenden Award in 2010. In 2008 he received the Distinguished Townsend Harris Medal from the City College of the City University of New York for his contributions to exploration seismology. He is the co-author ( with Bob Stolt) of a two volume graduate textbook on “Seismic Imaging and Inversion” published in 2012 by Cambridge University Press.