EFFECTS OF VERTICALLY ALIGNED SUBSURFACE FRACTURES ON SEISMIC REFLECTIONS - A PHYSICAL MODEL STUDY

We investigate the effects of subsurface fractures on moveout velocity and on reflection amplitudes by constructing a fractured model with t hree layers. The physical model was constructed by embedding a Phenoli tic disc within the intermediate layer, which acts as a zone of vertic al fractures. Survey lines were run along seven azimuthal directions b etween the strike direction and the transverse direction to the fractu res at an angle increment of 15 degrees. For our set of experimental c onditions, we observe that the horizontal moveout velocity decreases f rom the strike direction toward the transverse direction to the fractu res, and that the rate of decrease in amplitude variation with offset (AVO) increases from the strike direction toward the transverse direct ion to the fracture.