東京低地における強震観測

概要

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The average amplification characteristics of a sedimentary layer with a thickness of several kilometers in the Tokyo lowlands are estimated by using the SMACs records obtained during the moderate earthquakes which occurred beneath the Kanto district. The average amplification characteristics are given by the average of ratios of the zero-damped velocity response spectra of surface strong-motion to those of bedrock motion.The zero-damped velocity response spectra of bedrock motion are given through the prediction models which were constructed by using data obtained by accelerometers installed at the bottoms of deep boreholes in the pre-Tertiary basement. The amplification factors obtaines at about 1Hz, are found to depend on soft alluvial layer ; high amplification factors as high as 20 are observed. The estimated response characteristics of the representative sedimentary layer in the Tokyo lowlands are explained by taking account of a frequency-dependent Q, <I>i, e</I>., Q = 50f (f =0.5-2 Hz) and Q=100 (f = 2-10Hz).
社団法人東京地学協会の論文