Predicting of the Seismogram and Accelerogram of Strong Motions of the Soil for an Earthquake Model Considered as an Instantaneous Rupture of the Earth’s Surface

Abstract

Problems of the prediction of displacement and acceleration values for strong soil displacements are considered for the case where an earthquake is regarded as an instantaneous mechanical rupture of the Earth’s surface. We have attempted to develop, based on recent concepts of earthquake generation process, simplified theoretical methods for the quantitative prediction of soil displacement parameters during strong earthquakes. As an illustrative example, we consider an earthquake originating as a consequence of relative displacements of suddenly ruptured blocks in a horizontal direction with a given initial velocity. An empirical relationship between soil particle motion velocity near the rupture and at a certain distance from it, on one hand, and the earthquake magnitude, on the other hand, was established. It is assumed that the impact of inertial motions of a deep soil stratum on the inertial motions of upper subsurface soil stratum at instantaneous break of a medium can be neglected. By solving a wave problem for a multilayer near surface stratum, analytical relations were developed for a soil seismogram and accelerogram on the surface depending on the physical–mechanical and dynamic characteristics of the soil at all layers of the stratum; attenuation coefficients of mechanical soil vibrations; the distance to the rupture; and the magnitude of the predicted earthquake. The results obtained enable us to determine the maximum displacement and acceleration values of the soil, taking into account local soil conditions and their variations over time, as well as the values of the predominant vibration periods in the soil. The method was applied for solid and loose soil basements.