Abstract
I estimate short-period spectral level of acceleration source spectra for 7 intraplate earthquakes and 4 interplate earthquakes occurring around off Miyagi prefecture. It is found that the short-period spectral level for the 2003 Miyagiken-oki earthquake (MJ7.0 intraplate earthquake) is higher than that for the 1978 Miyagiken-oki earthquake (MJ7.4 interplate earthquake). On the average the short-period spectral level of intraplate earthquakes occurring off Miyagi prefecture is a factor of 4 to 6 higher than an previous empirical relation for crustal earthquakes and a factor of 3 to 4 higher than that interplate earthquakes occurring off Miyagi prefecture. This feature is similar to that for intraplate and interplate earthquakes occurring off Fukushima prefecture.
