Abstract
In this paper, an attempt to develop the JMA (Japan Meteorological Agency) instrumental seismic intensity and its algorithm was made so as to be responsive to the seismic phenomena and earthquake damage features in wider period range. The range of natural period of man-made structure has, however, been spreading rapidly in both shorter and longer directions and new structures have been increasing in number as well. In this new situation, an advanced seismic intensity available for wider period range, say, from 0.05sec to 20sec, is expected to develop.
In this recognition, an attempt was made for a new instrumental seismic intensity that combines a set of three index values for short, medium and long periods respectively. The algorithm to evaluate the index values for medium and long periods are developed in parallel with a slight modification. Examples of evaluation for the Kobe earthquake and other recent major earthquakes in Japan revealed the importance of introducing such combined seismic intensity and the effectiveness for application to seismology as well as earthquake engineering.
