Three-component recordings: Interest for land seismic source study

Abstract

Three components of the ground velocity were recorded, from which particle trajectories can be constructed. The three-dimensional picture of particle motion shows a number of complex phenomena. Nevertheless this trajectory has predominant directions of polarization. Spatial directional filtering can be used to calculate the polarization axis of parts of the trajectory. This filtering can reject the parts for which the angular gap between their polarization axis and a reference direction (for example X, Y, or Z) is greater than a given threshold angle. Several land seismic surveys with 5 different sources were recorded with triphones. Using spatial directional filtering with threshold angles varying from 0 to 90 degrees, we evaluate the quantities of energy emitted in each principal direction X, Y, or Z. We obtain a set of diagrams which can easily be used to compare the behavior of each source and to calculate their efficiencies in X, Y, or Z directions. The study of seismic sources presented here is, in fact, a specific application of three-component recordings. Taking into account a spatial directional filtering (SDF), we want to characterize different land seismic sources by their relative wealth of emission of polarized waves along specific directions in space.