Research On Using Inverse Scattering Series To Attenuate Multiple

During seismic surveying, a seismic source is repeatedly actuated and seismic receivers, such as hydrophones in marine seismic surveying, receive energy direct from the sources and reflected from various boundaries or interfaces. In the case of marine seismic surveying, energy propagates into the earth and is reflected back to the hydrophones from subterranean boundaries or interfaces, for instance between strata of different types. The recorded seismic data can be processed to reveal information about the structure of the earth in the area being surveyed. However, such reflections are contaminated by other reflection paths. For instance, energy from the sources is reflected at the sea surface directly to the hydrophones. Also, energy can be reflected more than once between the sources and the receivers. Such multiple reflections can take place within the earth. Also, energy initially traveling downwards from the sources can be reflected upwardly and then downwardly again from the surface of the sea before arriving at the hydrophones. Reflections of this type are referred to as "free surface multiple reflections". Free surface multiple reflections can be classified according to their order, which is equal to the number of reflections from the free surface. Thus, fist order free surface reflections comprise energy initially traveling downwardly from the sources (as opposed to "ghosting" where travels upwardly and is reflected from the free surface), is reflected upwardly from the sea bed or a boundary below the sea bed, and is then reflected downwardly from the free surface to the hydrophones. Second order free surface multiple reflections undergo two downward reflections from the sea surface before being detected by the hydrophones, and so on. This determining method is also suitable to the case of internal multiples.A given order free surface multiple was generated by a term in the forward series and attenuated by another term in inverse series. The situation for internal multiple is quite different, generating internal multiples of a given order in forward series required an infinite series, it is these infinite series that we use to attenuate internal multiple in the inverse series. The particular inverse scattering subseries for attenuating internal multiple we describe here chooses only the leading and the most significant contributions from the inverse removal series of each order of each of multiple, forming a series that attenuate well rather than eliminate all the internal multiples.