抄録
In this serial paper part 2, the physical mechanism of producing the spectral characteristic of ground motion at ground surface was firstly discussed. A surface layer was represented by a physical model in which the filter and amplifier properties of the layer were considered. Those two properties can be easily obtained from observation. Therefore, the frequency characteristic of ground motion can be obtained by multiplying every frequency component of two spectra of surface layer and input earthquake appeared on bed rock. In order to confirm the suitability of above method, the spectrum made through the method was compared with that obtained from a simple model by ordinary means. This comparison proved that the both spectra were very similar to each other. The method of reproducing the original ground motion from a given spectrum was presented which was the main subject of this study. In this case, the changes in spectral characteristic and power according to the elapse of time were taken into account. As an example, this method was applied to the prediction of Tokachi-Oki earthquake which would occur at the ground surface of Hachinohe Technical College, which was one of the heaviest damaged buildings. The spectral characteristic of the ground had been observed by several after-shocks. Using the spectrum and the record of strong motion accelerometer installed at Hachinohe Harbor, the ground motion at Hachinohe Technical College could be successfully presumed. The maximum accelation of which was indicated to be 291 gals, which is 30 percent larger than that of the record at Hachinohe Harbor. However, the maximum acceleration response for the ground motion of Hachinohe Technical College was found to be abut 2.3 times that of Hachinohe Harbor. That should be one of the most significant reasons which caused to the heavily structural damage.
