Formulation of hybrid approach for theoretical seismograms using thin layer element and axisymmetric finite element. Sanjigen hakuso yoso to jiku taisho yugen yoso no hybrid ho wo mochiita riron jishin do no keisan hoho

This paper presents a new method to calculate theoretical seismograms for earth structures considering the layered strata and local soil conditions surrounding an observation point. The reciprocal relationship of Green's functions is employed in the formulation, and the Green's functions are obtained in the frequency domain by combining the three-dimensional thin layer elements developed by Waas, Kausel and Tajima and the axisymmetrical finite elements. The results in the time domain are obtained by the FFT algorithm. Therefore, the proposed method is called the thin layer finite element (TLFE) method in this report. The accuracy of this method is examined by comparing its results with wave number integral solutions for a buried point source in an elastic halfspace. As a numerical example, theoretical seismograms on the idealized sedimentary basin model are calculated in order to illustrate the effect of local soil conditions surrounding the observation point.