The dispersion of Rayleigh waves South of the Gulf of California

Abstract

The inversion of observations of surface wave dispersion has been much used to determine the structure of the earth, especially the outer parts. In a region as well populated with earthquakes and as sparsely populated with seismographs as Mexico, single-station methods for the determination of the dispersion are more likely to be practical to apply tan triangulation methods involving the establi shment and synchronization of arrays of seismographs. In the single-station methods, the earthquake is assumed to have an impulsive time-dependence for the motion at the focus. More properly. it is assumed that the Fourier components of the focal motion are all in the same phase. For the purposes of doing regional mapping of structure, observations at small epicentral distances are preferred so that the surface waves cross as few dissimilar regions of geologic structures as possible.