17 QUAL I TÉ GÉOPHYSIQUEAPPLIQUÉE 1 Wave propagation 3 J.-L. Mari Seismic prospecting consists of the generation of very low-amplitude artificial earthquakes at predetermined times and positions. The seismic disturbances generated by a seismic source are recorded by a seismic receiver spread. The acquisition geometry is defined by the distribution of the source spread and the receiver spread. The following elements are needed to observe the propagation of seismic, acoustic or elastic waves: 1. A source spread. The source is a device capable of producing a deformation in a medium. In land acquisition, it can be an explosive charge (dynamite), a weight dropper or a vibrator. In marine acquisition, it can be an air gun, a sparker or a vibrator. Seismic energy radiated by the source is split between body waves (compressional and shear waves) and surface waves. 2. A physical medium defined by its geometric and mechanical characteristics. Here we consider the geological formations defined by the following mechanical properties: • Propagation velocity of the compressional P-waves in the rock: VP (expressed in m/s), This chapter of Seismic Imaging: a practical approach is published under Open Source Creative Commons License CC-BY-NC-ND allowing non-commercial use, distribution, reproduction of the text, via any medium, provided the source is cited. © EDP Sciences, 2019 DOI: 10.1051/978-2-7598-2351-2.c003
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