Imaging Within Complex Velocity Structures with General Acquisition Geomtry
High frequency linearized inversion estimates a critical component of the earth's velocity field from measurements of scattered acoustic waves captured in various acquisition geometries. The method partitions the velocity field into two components: an assumed long scale velocity component and an unknown short scale velocity component. In strongly refacting (complex) velocity fields, several scattering paths (pairs of incident and reflected rays) with equal traveltimes produce artifacts in the short scale velocity's inverted image. This article explains how to determine whether images for certain acquisition geometries and long scale velocity fields will be artifact-free. To produce an artifact-free image in a complex velocity field, scattering paths must be reconstructable from two pieces of information: (a) The traveltime for the pair of rays and (b) The projection of the rays into the phase space of the source-receiver configuration. Numerical illustrations confirm that a point source can produce artifacts if a caustic develops in the incident ray field. A new acquisition geometry achieved by averaging several point source images adds information to (b) and thus removes these artifacts.
Citable link to this pagehttps://hdl.handle.net/1911/101874
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