The contribution of reflected, refracted and transmitted waves to seismic tomography: a turorial

Abstract

Introduetion Traveltime inversion usually treats only reftected and transmitted arrivals. This is due to two main reasons: first, in conventional hydrocarbon exploration, acquisition and processing parameters are optimized for these type of waves, whereas others (e.g. refracted or diffracted) are attenuated as an undesired noise; secondly, the most popular ray tracing techniques (based on Snell's law or on the eikonal equation) are not ab Ie to model refracted or diffracted waves. During the last few years, various techniques based on Fermat's principle have been proposed which enable us to exploit these events also (see among others Moser 1989, 1991; Saito 1989; Asakawa and Kanawaka 1993; Fisher and Lees 1993). The algorithm adopted here, in particular, allows us to trace the minimum time paths of refracted and diffracted waves in irregular grids (Vesnaver 1993).