A DIRECT METHOD OF CALCULATING INTERVAL VELOCITIES AND LAYER THICKNESSES FROM WIDE-ANGLE SEISMIC-REFLECTION TIMES

Wide-angle reflections are now routinely recorded in high resolution e xplosion seismics to study the crustal structure. Use of Dir's hyperbo lic approximation to the nonhyperbolic wide-angle reflection travel ti mes causes major errors in the determination of interval velocities an d layer thicknesses of a stack of horizontal velocity layers. Here we propose a layer stripping method to directly calculate the interval ve locities and layer thicknesses in a vertically heterogeneous earth fro m the strong and reliable wide-angle reflected events. Synthetic refle ction travel times, at wide-angle range, for a given velocity model, c ontaminated by some random errors, have been used to demonstrate the r eliability of the algorithms to determine the interval velocities and thicknesses of various layers. The method has also been tested on two field examples along two deep seismic sounding (DSS) profiles with wel l identified wide-angle reflection travel times, which illustrates the practical feasibility of the proposed method.