In this study, we propose a method of evaluation of an acceleration response spectrum at local government sites which lose seismic waveform records in case of crustal earthquakes. The proposed formula considers the relation between the predominant period of spectrum and the natural period of structure as a parameter in addition to A₀/A(a ratio of effective acceleration to PGA) used in the past studies. The result of analysis shows the proposed method can evaluate not only the peak value but also the shape of response spectrum.

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Seismic wave energy in surface layers is calculated based on vertical array records at 30 sites during 8 strong earthquakes recently occurred in Japan by assuming vertical propagation of SH wave. The upward energy tends to decrease generally as it goes up from the base layer to the ground surface particularly in soft soil sites due to drastic impedance changes at soil boundaries. Hence, only 30% of the upward energy reaches to the ground surface at the maximum, and about 30-40% of that or less tends to dissipate in the ground shallower than the deepest point with the rest 60-70% returning to the earth again, in most sites studied here. It is also found that the upward energy at the depth of around 100 m may be roughly evaluated for engineering purposes by a simple equation based on the spherical energy radiation from focal points.

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 During the 2008 Iwate-Miyagi Nairiku earthquake in Japan (M_J =7.2), extremely high accelerations were recorded at the KiK-net IWTH25 (Ichinoseki-nishi) station. The peak acceleration in the vertical component of the surface record was about 4 g where g is acceleration due to gravity, and the upward acceleration in the surface record was much larger than the downward acceleration. Some researchers have suggested that the ground surface was tossed into the air like a body on a trampoline. However, additional features found in the surface record suggest rocking motion accompanied with downward impact of the station with the ground. For example, there are many vertical peaks that can be found to occur at the same time as the horizontal peaks. After obtaining information about the station, in-situ investigations, shake-table experiments, and numerical simulations were conducted to determine the fundamental characteristics of the rocking motion and to reproduce the acceleration time histories of the surface record by using the bore-hole record at a depth of 260 m as the input motion.
 Prior to the numerical simulation, the wave velocities of subsurface layers were evaluated from Fourier spectra of both records, which showed that the velocities were reduced considerably during the main shock. A 2-D FEM code capable of handling separation and impact between the elements was used for the numerical simulation. Simulation results are shown in Figs. 17 and 18 indicating the impact between the IWTH25 station and the ground at around 4 sec when the acceleration in the vertical direction was about 4 g. Three kinds of acceleration time histories are shown with fairly good agreement between the simulated and observed time histories, suggesting the influence of the station is included in the record. It is also indicated that the vertical acceleration at the free surface without the influence of the IWTH25 station is about 1.6 g.

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Seismic intensity distribution around Omaezaki-city was estimated from the roof tiles damage by the 2009 Suruga Bay Earthquake. First, roof tiles damage rate distribution was made using air photographs. We could easily distinguish roof tiles damage by air photographs. Next, period range of strong ground motions which correlates with roof tiles damage was investigated. We found that roof tiles damage correlate with JMA seismic intensity. Then, vulnerability function of roof tiles damage by JMA seismic intensity was made, and JMA seismic intensity distribution was estimated using this function. The JMA seismic intensity varies very locally. We found that JMA seismic intensity distribution can be estimated from roof tiles damage data by air photographs, but some problems were found such that we need sufficient number of wooden houses with roof tiles and that we could hardly distinguish wooden houses with roof tiles from house with no roof tiles.

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Many people stay and study at classrooms in a university campus, which may result in dangerous situation during and after earthquake disasters. This paper conducted fundamental simulations on evacuation from a disaster to improve the safety of the university campus. The results showed that the evacuation process had three stages related to the usage of several exits. The evacuation guidance was insufficient for some cases, whereas the capacity-enhancing of the doors had good effect.

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The Central Disaster Management Council constructed 3D subsurface velocity structure models to conduct the strong motion simulations and described the map of natural periods which calculated using the subsurface velocity structures. We evaluated the amplification of long-period component of seismic records, and confirmed that the natural period which calculated from velocity structures related to the amplitude of long-period component of ground motion. The relation was that the longer the natural period at the observation station was, the larger the amplification of long-period component of observed record was. We proposed new attenuation relationship using the relation of natural period and amplification of long-period component of ground motion.

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