Introduction

Abstract

The region of the earth down to about 100 km is called the lithosphere. Rigorously speaking, lithosphere refers to the solid portion of the earth that overlays the low velocity zone or the asthenosphere, and the thickness varies from place to place depending on the tectonic setting; however, we will use this term loosely for the upper 100 km of the earth that consists of the crust and the uppermost mantle. The structure of the earth’s crust has been investigated using layered models since the discovery of the Mohorovicic discontinuity or Moho at the base of the crust [Mohorovicic, 1909] and the Conrad discontinuity in the mid crust [Conrad, 1925]. The characterization of the earth as a random medium is complementary to the classical stratified medium characterization.