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 (M_J7.0 intraplate earthquake) is higher than that for the 1978 Miyagiken-oki earthquake (M_J7.4 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.

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To evaluate the cause of damage and damage process of still pipe pile foundation structure in a reclaimed island damaged during 1995 Hyogoken-nambu earthquake, dynamic analysis by using multi-lumped mass and spring model and static analysis by using a model of piles supported by Winkler type springs were conducted. At first superstructure was damaged by strong motion before liquefaction, and large bending moments beyond the ultimate plastic moment appeared at G.L.-6m near the water level and around G.L.-15m, the lower boundary of “Masado” caused by large deformation of ground during accumulating process of excess pore water pressure. At last, piles deformed residually due to liquefaction-induced lateral spreading of the ground towards the quay walls after liquefaction. These methods mentioned above could explain the cause and process of pile damage during the earthquake.

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Motion tracking with optical devices such as surveillance cameras can be particularly powerful for measuring earthquake induced motions. We propose a vision-based system with motion tracking for providing additional safety functions to detect seismic damage to interior elements and thus reduce risks in a building. Shaking table tests were carried out to evaluate the system's ability to detect structural collapse and overturning of interior elements using conventional video cameras. Results from this exploratory study show that vision-based measurements are promising in terms of capturing small to large deformations and identifying various kinds of seismic damage.

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Adequate evaluation of the strong motion characteristics is indispensable for quantitative strong motion prediction. In this paper, separation of source, path, and site characteristics was carried out by the spectrum separation technique based on the observed data of K-NET, KiK-net, and the JMA Shindo-kei network in Japan. We analyzed 228 sources and 1, 700 sites. As for the source characteristics, we found that among three different types of earthquakes, namely plate boundary, intraplate, and crustal ones, Brune's stress drops are significantly smaller for crustal earthquakes, and that they does not linearly correlate with depth. As for the propagation path effects, we found Q value in the back arc side of a volcanic front to be about one half of the front arc side, and Q for inland earthquakes seems to be equally high as those for plate boundary and intraplate earthquakes.

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