This study characterizes evacuation behavior in Ibaraki Prefecture in the aftermath of the Great East Japan Earthquake and tsunamis based on geographic information, questionnaires, and interview surveys. We identified several factors on which the starting time of evacuation depended, including awareness of evacuation warnings, understanding of anticipated tsunami inundation areas (hazard maps), and distance from anticipated inundation areas. We found that those who were aware of evacuation sites, hazard maps and/or anticipated inundation areas maps, and who lived in inundated areas tended to evacuate earlier. Conversely, many residents delayed their evacuation because they chose to go home and take care of their family first. To improve future responses to likely threats, evacuation behavior and local disaster management plans must be reviewed based on the knowledge gained from this disaster.

View full abstract

The effect of rupture starting point uncertainty on the prediction of long-period ground motion using a source model was examined regarding the hypothetical Tokai Earthquake. Monte Carlo simulation with a sample size of 30,000 was conducted assuming that the rupture starting point is uniformly distributed in the fault to calculate the statistics of the ground motion. The results of numerical simulations revealed that the maximum values of velocity response spectra in the long period region are well expressed by TYPE III extreme value distribution. The presence of an upper limit in this statistical distribution was also pointed out by using the extreme value statistics theory.

View full abstract

After destructive earthquakes, objective and quantitative evaluation of building damage is significant for determine making of continuous use or reinforcement, which is the first step of recovery activities. Based on the declination of natural frequencies of building systems, damage evaluation of global buildings including soil-structure interaction can be performed. In order to evaluate building damage of inter stories rather than the whole building, in this paper, inter-story shear-wave velocities are extracted from microtremor records of a damaged 9-story SRC residential building based on the deconvolution method. A relationship between shear-wave velocity and the story rigidity of buildings is proposed. Using this relationship, the shear-wave velocities of a design example are calculated and compared with those of the damaged building. Story-by-story building damage evaluation is performed.

View full abstract