Estimation of Probable Ground Vibration Spectra and Reaction Spectra Taking into Account Local Ground Conditions

Statement of the problem. Using the example of a strong earthquake that occurred in Dagestan in 1970 with a magnitude of M = 6.7, practical methods and results of forecasting the variable Fourier spectra and reaction spectra, taking into account the characteristics of the focal zone and local ground conditions under strong seismic influence, are shown. It became possible to consider the variability of reactions associated with the randomness of the phase angle of individual harmonics of the general oscillation and the uncertainties of the parameters of the ground oscillation. In turn, this will allow us to obtain a set of regional or local reaction spectra with given probabilities of not exceeding the loads, which allows designers to choose the initial loads depending on the type of building or structure (depending on the degree of its responsibility). Results. The reliability of estimates of Fourier spectra and reaction spectra obtained during a single event allows us to solve the problem of assessing seismic hazard in terms of Fourier spectra and reaction spectra. But, it should be noted that this method of assessing the seismic load can lead to an increase in the cost of construction, since in this case we lay the load with a large margin, so this technique is applicable for the design and construction of buildings and structures in which deformations are unacceptable (nuclear power plants, etc.). Conclusions. Consideration of soil factors in the probabilistic formulation should be carried out in the presence of a large amount of experimental data on the composition, properties and reaction of this type of soil, allowing to construct the probability density functions of the distribution of spectral characteristics, as well as the characteristics of the focal zone.