Appendix B: Waves at a Free Surface
In Chapter 3, we derived formulas that describe how the scalar amplitude of particle displacement changes along a ray. However, in a seismic survey, this scalar amplitude is not directly recorded because the geophones or hydrophones are at a free surface. This appendix addresses how the described scalar amplitude of particle displacement can be computed from land-seismic three-component free-surface recordings. It also addresses how pressure is described in a sea-seismic survey. The formulas in this appendix are based on the conversion coefficients given by Červený et al. (1977).