短周期地震波の位相速度の検出法

Abstract

For civil structures extending in horizontal direction, such as suspension bridges, elevatedbridges, buried pipelines and banking structures, phase change along propagation path ofseismic wave in rather short period range is essential information for assessing the safetyof civil structures against a seismic environment. Especially the knowledge of the phasevelocity of seismic wave is indispensable for the seismic response analyses of those structuresin which the relative deformation between two supporting points becomes crucial.We compared several methods to calculate appropriate phase velocity from a seismicwave. Phase velocity is usually very sensitive to the level of noise contaminating the signal.To overcome this defect we have developed a new method to remove the noise effect usingKalman filter technique. Phase velocities were detected from noise contaminated synthesizedmotions which were generated using artificial dispersion curve. Calculation of phase velocityshows that Kalman filter technique can be used for earthquake records with low SN ratio.Comparison of detected phase velocities has also been done for earthquake records of theEl Centro earthquake.