Rapid inversion in shallow water with a single receiver using modal time-frequency pattern extraction

This paper presents a new inversion method in shallow water (0–400 m) for impulsive low-frequency source (0–200 Hz) using a single static receiver. In this configuration, propagation is described by modal theory. The recorded pressure field can be decomposed into modes whose arrival times (which are frequency dependant) contain information about environment. However, modes share a common frequency band; and when the radial distance between source and receiver is smaller than 15 km, modes are also overlapped in time on the receiver. In this case, adaptive signal processing is required to identify them. First, modal propagation is quickly reviewed. Secondly, it is shown that environment information is embedded in the time-frequency structure of the modes. Then, a new inversion algorithm -simple and computationally light- using the modal arrival times is presented. Finally, it is applied on noisy simulated data.