Relationship between Building Damage Ratios and Ground Motion Characteristics during the 2011 Tohoku Earthquake

Abstract

Fragility curves, the relationships between three kinds of building damage ratios, i.e., total collapse ratio (TCR), collapse ratio (CR) and damage ratio (DR), as well as ground motion characteristics, i.e., peak ground acceleration (PGA), peak ground velocity (PGV), Japan Meteorological Agency instrumental seismic intensity (IJMA) and spectral intensity (SI), were studied for the 2011 Tohoku Earthquake. It was found that the DR was related better to ground motion characteristics than the TCR and CR during this earthquake, and the correlation between the DR and any one of the PGV, IJMA or SI indices was almost the same. The DR during the 2011 Tohoku Earthquake reached almost the same level as that during the Kobe Earthquake for the same level of ground motions. There were some districts where the DRs did not always correspond to reasonable levels of ground motion characteristics. One reason for this was considered to be the representativeness of the ground motions over each district. Thus, one method of estimating ground motions at damaged sites was proposed by using the underground velocity structures identified from the H/V spectral ratios of microtremors, after we confirmed the consistency of the H/ V spectral ratios between earthquakes and microtremors. It is expected to be used for the construction of fragility curves with greater accuracy.