DEVELOPMENT OF SYSTEM FOR EVAUATING SEISMIC GROUDA MOTION AND HAZARD IN IRREGULARLY STRATEFIED LAYER BASED ON MICROTREMOR MEASUREMENTS

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The object of this study is to develop a method for estimating shear wave velocity structures as well as ground motions and resulting hazards in the area involving irregularly stratified deposits, based on microtremor measurements using either array of sensors or a single sensor, or a combination of both. For this purpose, (l)data acquisition system is developed for extracting surface wave characteristics (I.e., dispersion data and H/V spectra) in microtremors ; (2) analysis method is developed to estimate one and two-dimensional shear wave velocity profiles based on the inversion of either microtremor dispersion data or H/V spectra, or both ; (3) microtremor measurements are conducted at several arias where shear wave velocity is known and the effectiveness of the proposed method is examined ; (4) strong motion array observation is also conducted in one of the areas to characterize spatial variation in ground motions across irregularly stratified deposits ; (5) two-dimensional dynamic … More response analysis is conducted to evaluate ground motion characteristics in the area and to compare with the observed records; and (6) the effects of surface geology on building damage is examined at the areas of building damage during recent strong earthquakes, based on the proposed method and analysis.It is shown that(1) The one- and two-dimensional shear wave velocities determined by microtremor measurements using either array of sensors or a single sensor, or a combination of both, are consistent with available geological information, indicating that the proposed method is effective in geophysical exploreation.(2) The two-dimensional dynamic response analysis can simulate reasonably well the observed spatial variation of ground motions, indicating that the proposed method is also effective in site response evaluation.(3) The spatial variation of ground motions and building damage during recent earthquakes are strongly affected by the effects of surface geology and can readily be estimated by the proposed method. Less