Japan Marine Sci. and Technol. Ctr., 2-15 Natsushima-cho, Yokosuka 237, Japan
Two one-way transmission experiments (1989) and one reciprocal transmission experiment (1991) have been conducted by JAMSTEC. These experiments were in the 200--300 km range and were less than 4 days in duration. The data of mooring motions were not available in the experiments. This tomography method, which can work well with the limited data, is made up as follows. The reference data are constructed with the data supplied by JODC. The ray-tracing code based on the generalized ray theory [H. Weinberg, J. Acoust. Soc. Am. 58, 97--109 (1975)] is range independent. The identification of multipaths is accomplished by means of linear ray identification. The bias component in travel times is corrected using a linear tomography inversion. The covariance function of sound speed is a Gaussian [Chiu et al., J. Geophys. Res. 92, 6886--6902 (1987)]. The estimator is constructed by the simple stochastic inverse theory. The map is a 1-D and 2-D time series of a sound-speed anomaly and a temperature anomaly. The three-dimensional tomography method is now under consideration.