Itaru Uchida

Evaluation of Ground Vibration Characteristics of Mashiki Town Affected by the 2016 Kumamoto Earthquake

Takaaki Ikeda

In the Kumamoto earthquake in 2016, there were two earthquakes that recorded a seismic intensity of 7 in a short period of time. Many damaged houses have occurred, but we do not know which was damaged by the shake. Therefore, in order to reduce future damage, it is necessary to ascertain the cause of the damage. For that reason, we estimated the progress of building damage by aerial photograph which can grasp the damage situation with temporal change.
In order to objectively judge building damage judgment by aerial photograph, the roof damage area ratio of the building was used as an index of damage. Therefore, we used a photograph of orthogonally transformed aerial photographs taken vertically from just above which we can quantitatively determine the area. Based on the index called Damage Grade, the damage classification was divided into 5 stages, building damage was evaluated, and damage progression of the building was confirmed from after the pre-quake to after the main shock. We verified the judgment accuracy of the damage estimation done in this study from the photograph obtained in the field survey and judged that it was able to make a judgment with high precision with respect to judgment of "Damage Rank D" which is equivalent to collapse / collapse equivalent to "no damage" confirmed. Estimation of the ground vibration characteristics that can be considered as one of the factors due to differences in the damage situation in a narrower range at all times by the primary natural period by microtremor measurement, and when building damage and ground vibration characteristics are compared, it has been confirmed that extensive damage occurred in places where the natural period of the building and the primary natural period of the ground are close.