HangingWall and Footwall Effects in the Largest Reverse-Slip Earthquake of Turkey, October 23, 2011, M_W 7.2 Van Earthquake

摘要

This study provides an engineering-focused assessment of the ground motions recorded during the M-w 7.2 reverse-slip Van earthquake. Spatial and temporal distributions of the site responses and their effects on the structural responses were discussed. Reverse/oblique earthquake characteristics with coupled effects of source, path of propagation and local site conditions in the fault-normal and fault-parallel directions on hanging wall and footwall blocks are particularly considered. Magnitude and distance dependency of the recordings from 22 stations were examined using ground motion prediction equations developed for reverse mechanism. Results show that parameters in the ground motion prediction expressions are not robust enough to represent the source process and propagation effects. Elastic and inelastic displacement limits for the first three closest stations are exceeded in each direction for structural periods greater than about 0.2 s. Severely damaged towns Erci and Van were examined in the lights of available recordings. Large structural displacement responses of the majority of the buildings initiated inelastic behavior during the main shock. As a consequence of severe demands, structural collapses observed at the region due to poor construction quality which satisfied neither nominal nor full ductility levels. Overall results indicated that effects of directivity and hanging wall effect increased the influence of the seismic loading on structures despite low peak acceleration values recorded at the region. For known active tectonic regions, earthquake design spectrum should be modified over a period range of interest for rupture dynamics and near-fault ground motions in strike-normal and strike-parallel directions.