New method of processing records of seismic oscillations based on analysis of correlation functions of amplitude and phase fluctuations part 1. Results of the method using in numerical model experiment

Method of analysis of correlation functions of random fluctuations of amplitude and phase (CFAP) is used for processing time records of a point displacement in elastic medium. The first part of the study deals with properties and peculiarities of CFAP dependences on the phase shift τ of oscillations of points on free surface. These properties were examined through numerical experiment for the model of plain infinite layer. It appeared that under certain conditions for the model parameters the dependencies of CFAP on τ were in the form of sequence of peaks with the same interval ∆ between them. For this interval, the correlation was found with some of model parameters, and the empirical formula was constructed. It turns out that ∆ is determined by the period of oscillations being processed and traveling time (there and back) of P- or S-wave vertically down from the source to the surface reflecting waves. In the second part of the study, this empirical formula and revealed CFAP peculiarities are used for processing parts of record of real seismic oscillations at the station Talaya (Eastern Sayan) by the suggested method. First experiments of the processing showed that the dependencies of CFAP on τ for some portions of oscillations show a striking similarity with CFAPs which were obtained in the numerical experiment. It means that when determining the interval ∆ of real oscillations and using its empirical formula we are able to measure the mentioned traveling time between the source and the reflecting surface tA. After processing the earthquake records according this scheme, the sequences of time measurements tA were obtained, and distributions were constructed for four different sources epicenters of which were located in western part of the Pacific Ocean. Analysis of the distributions allows us to conclude that the layer of solid matter of a thickness about 70 km is located in the region of sources at a depth of 400 km. Moreover, the possibility of measuring the mean velocity of P- and S-waves at intervals of different depth of upper mantle is shown. Measurements can be realized not by indirect way but by direct one as the ratio of a distance and time during which a wave passes this distance. Measurements of these velocities in the region of Santa Crus islands at a depth from 33 to 90 km show the values VP=(6.4±1.2) km/s, VS=(3.0±0.2) km/s.