Estimation of current profiles by inversion of tomographic data

Abstract

Pulse traveltime data contains information in combined and integrated form on both sound velocity and currents. Inversion methods can be generalized so as to yield estimates simultaneously of sound velocity and current vector components as functions of position. We are concerned with establishing bounds on the estimates derived from inversion procedures. One such procedure is described. In this approach, the estimate of one of the unknown functions may be interpreted as a weighted local average of the actual function with contamination by the other unknown functions. Statistical error may also be included in the analysis. The quality of the inversion is determined by the degree to which contamination is minimized; this is a function of the geometry of the tomographic configuration. Examples are presented for a horizontal ocean slice. The inversion may be performed with or without reciprocal transmissions (interchange of sources and receivers); however, their use dramatically improves isolation of sound velocity from the current vector.