Three-dimensional seismic endoscopy. I. Design of apparatus and basic imaging algorithms

A method, called "seismic endoscopy," able to perform three-dimensional (3-D) acoustical imaging in a cylindrical volume around shallow-depth boreholes is described. The main characteristics of borehole tools designed and constructed in the authors' laboratory are presented. Several tests performed in an acoustical water tank are used to illustrate the basic imaging algorithms adapted to the particular acquisition geometry of the probes. In particular, both the filtering of borehole waves and azimuthal refocusing are discussed.