Site Effects and Building Damage Characterization in Concepción after the M_w8.8 Maule Earthquake

The influence of site effects on seismic demand was studied in Concepción to explain the observed damages suffered by engineered structures during the 2010 M_w8.8 Maule, Chile, earthquake. Shallow shear-wave velocity ( V_S), site period, and gravity measurements were used to assess site effects. The three-dimensional (3-D) basin shape was inverted from gravity values. Predominant period shows a good correlation with bedrock depth, suggesting that V_Sof soil is relatively uniform throughout the city. This was confirmed by direct V_Smeasurements at 17 sites throughout the city. The irregular distribution of damage suggests that V_S30is not a good proxy for damage distribution in Concepción. In contrast, we observe dependence with basin thickness, site period, and estimated PGV for buildings with high vulnerability. Most low-vulnerability structures showed no damage regardless of site conditions and intensity measures. Our results indicate that site effects contributed to structural damage in vulnerable structures and these effects were primarily controlled by basin depth.