Abstract
The JMA scale of seismic intensity has ten degrees by using the instrumental seismic intensity. The filtered acceleration amplitude, a0, used for the instrumental seismic intensity is a value that the accumulated time for acceleration larger than a0 is 0.3 second in the time history of acceleration. The effect of the acceleration in the remaining time history is not considered. The time history expression of seismic intensity using the running r.m.s. method will be discussed and compared with the instrumental seismic intensity in the paper. A modified seismic intensity is proposed by using a parameter which shows an extent of the seismic intensity with time.
