Preliminary processing of physical modeling data from circular arrays

David C. Henley

Many novel transducer arrangements are possible for detecting and imaging targets in a physical modeling tank. We describe here some early developments in the processing used to extract useful target information from a physical model in which the acquisition geometry consists of a circular array of discrete receivers surrounding an unknown target, with sources regularly placed on the same circle as the receivers. Each source gather consists of recorded signals from all the receivers on the circular array accessible to that source, subject to the mechanical positioning limitations of the modeling system. Essentially, this experiment attempts to extract the 2-D shape of the object enclosed by the array, using principles of transit-time tomography and back-projection. Since target information in this experiment consists of variations of direct-arrival transit times from those expected for an empty circular array, our processing efforts are aimed at detecting those variations, projecting them as "shadows", and using various geometric processing tricks to combine the shadows in the processed source gathers to form a crude image of the target, for use as the starting point in an FWI procedure.