Abstract
Various earthquake motion indices, maximum acceleration PGA, maximum velocity PGV, instrumental seismic intensity Ijma, SI value and RI value (maximum of real-time intensity RI), are compared each other. The PGA limited less than 5Hz (5HzPGA) is not differ form SI value that seems to be related to actual earthquake damage, form the relationship to the Ijma. Both Ijma and SI value are almost equivalent to the RI value that defined based on the power of the earthquake motion. It suggests that these indices mutually related to the actual damage. Because Ijma defined by JMA can calculate only after the earthquake and SI value must be calculated from responses for various periods, it is difficult to calculate without delay so both indices are unsuitable for the earthquake alarm. Because not only RI fits to the Ijma at the peak value, but also RI responses to the P wave arrival sensitively, RI can realize the quick and exact alarm. It is expected to beutilized at the various field because RI is assured to related physically to actual damage.
