Extraction de la fonction de Green de l’onde de Rayleigh par calcul de l’intercorrélogramme du bruit sismique

Abstract

Methods of Earth imaging are based on either passive sources (earthquakes) or active sources (seismic refraction or reflexion). The use of these various methods is limited, on one hand by the non homogeneous distribution of earthquakes over the Earth and, on the other hand, by the urban context of studied areas as well as by the investigating depth. In this work we apply a new approach using only records of seismic noise, which allow to calculate the dispersion curves of Rayleigh waves propagating between pair of seismic stations. This method consists in crosscorrelating records of seismic noise collected on long enough time durations (1 month or more) in two stations. The objective of this research training course was two fold ; on one hand, to learn this method of imaging the Earth in the framework of an seismological observatory, on the other hand, to Write a Matlab software capable, from records of seismic noise, to calculate the dispersion curves between permanent seismic stations whose data are accessible by the Internet network. The software is tested and validated on data already used by previous studies. The results are satisfactory. Also, an application of the method and of the software was made for data collected on seismic stations located on the Kaapvaal craton.