IMPROVEMENT OF SWEEPING METHOD IN IDENTIFICATION PROBLEM OF SUBSURFACE GROUND STRUCTURE AND ITS APPLICABILITY

Abstract

Vertical array observations of ground motions have been energetically carried out in Japan. They give us important information to identify the dynamic properties of subsurface ground. Some methods were proposed for the identification of shear wave velocity and quality factor. The accuracy of the identification of shear wave velocity has been improved. However, the improvement of accuracy is not very notable in the identification of quality factor. In this study, the sweeping method, in which the quality facor is estimated only at the frequency where the quality facor is sensitive, is modified so as to enable the extraction of more reliable information. Applying it to the identification of KiK-net sites, the coherency of identified quality facor at the identical site using the ground motions in the different events of earthquake is discussed.