ABSTRACT
This paper deals with the lessons learned from the Hyogo-ken Nanbu earthquake (M = 7.3) which occurred in Kobe, Japan in 1995 and whose epicenter was shallow, namely, about 15 km in depth. Right after the earthquake, field observations were carried out to investigate the failure mechanism of structures. The results showed that certain structures, particularly a tunnel, were damaged by an unusual failure mechanism which might have been caused by high-frequency impulsive vertical seismic waves. However, in the results of measurements taken by accelerometers, there was no evidence of such high-frequency impulsive vertical seismic waves. Thus, in February of 1995, measurements of the ground vibrations caused by the aftershocks of the earthquake were initiated, and were continued for about two years. To measure the aftershocks, servo-type accelerometers (DC~100 Hz), were used; they differ from conventional earthquake accelerometers (SMAC-MDU) whose measurement range is limited to DC~30 Hz.
