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

Eduard Khachiyan

doi:10.11648/j.earth.20180704.16

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.

Highlights

One of the main objectives of earthquake engineering is to predict patterns of soil vibrations and their amplitude–frequency characteristics depending on local geological conditions during strong earthquakes
We consider a multilayer lithological column with a height H (Figure 2b–d), all layers of which at the moment t = 0 have initial velocity v (∆), according to formula (2a) and the data given in Table 1, as the pattern for the calculation of variations displacements and accelerations of soil particle movement on the surface over time
We developed a method of forecasting the acceleration and displacement values during strong soil dis placements induced by an earthquake considering it as an instantaneous rupture of the Earth’s surface

Summary

Introduction

One of the main objectives of earthquake engineering (engineering seismology) is to predict patterns of soil vibrations (a construction site, for example) and their amplitude–frequency characteristics depending on local geological conditions during strong earthquakes. Reliable data on the character of earthquake induced soil vibrations in the soil can be obtained only by records made during a real earthquake. Soil displacement can be recorded with a high degree of reliability at epicenters of mainly weak earthquakes and at a large distance from the epicenter during strong earthquakes. All seismically active regions have been characterized by a large number of such records. In both cases, these records (seismograms), in terms of their application to the evaluation of the seismic resistance of buildings, are of little real interest, since the stress level in structural units of a building construction induced by weak earthquakes, relative to maximum permissible level, is

Methods

Results

Conclusion