Earthquake Damage of Building Structures by the 1994 Far-Off-Sanriku Earthquake and Predominant Period of Microtremors
The Far-Off-Sanriku Eathquake with the magnitude 7.5 in JMA scale occurred 21:19 on December 28, 1994. The ground motion estimated as VI in JMA scale. The largest aftershock with magnitude 6.7 occurred on January 7, 1995, gave great damage to same region.The ground motion estimated as V. In Hachinohe city, complete collapse numbers of the building structures and housings were 66 at the main shock and 16 at the aftershock. Half collapse numbers were 354 at mainshock and 48 at aftershock. And partially destroyed housings were 10,756.
The Object of this study is to clarify the relartionship between this damage and the site ettects, which are topography, geology and microtremors.
1) The damages concentrated on terrace deposits and it's near field.
2) The predominant periods in the damaged area were 0.3-0.4 second.
3) The thicknesses of surface layers in the damaged area were about 10-20 m.
The Bullet in of Hachinohe Institute of Technology,17,pp.125-138