Effects of the Yufutsu Basin on Structural Response During Subduction Earthquakes

Abstract eng:
Sedimentary basins tend to increase the intensity of ground-motions and the resulting damage to structures. Although current U.S. seismic hazard maps do not account for the effects of basins, most ground-motion prediction equations for crustal earthquakes include basin amplification terms, which amplify spectral acceleration at long periods. For most subduction earthquake GMPEs, these basin terms have not yet been developed. In addition, none of the available GMPEs account for the effects of basins on ground-motion duration and spectral shape. These omissions are particularly important in the Pacific Northwest of the United States, because this region has several deep basins, and even without considering basin effects, subduction earthquakes contribute a large portion of the overall seismic hazard, particularly at long periods. This paper quantifies the effects of the Yufutsu basin in Japan, which is similar to the deep basin underlying the Seattle region. For several subduction earthquakes of varying magnitude, the effects of basins are evaluated by comparing ground-motion recordings from stations located inside and near the Yufutsu basin. Basin effects are quantified using spectral acceleration, significant duration, and a new ductility dependent spectral shape intensity measure, SS a . The results of collapse analyses are reported for a set of well-studied archetypical building frame models, for which the ground-motion intensity at collapse is explained in terms of the three intensity measures. Finally, design strength amplification factors are developed with the aim of achieving collapse margin ratio for structures located inside basins during subduction earthquakes that are similar to those achieved by conventional structural designs.

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