The aftermath of 2011 Van earthquakes: Evaluation of strong motion, geotechnical and structural issues

October 23rd, 2011 M_L6. 7 (M_w7. 2 KOERI) Tabanli-Van Earthquake caused damage in a widespread area specifically in the settlement regions throughout the Lake Van. A number of 58 buildings totally collapsed during the shake with 52 of them however, reported to be in Ercis district. 17 days after this destructive event, another earthquake of M_L5. 6 hit the region again on the 9th of November having the epicentral location at Edremit district. The second earthquake mostly affected the central region of Van province with a number of 25 totally collapsed buildings and furthermore it significantly increased the existing structural damages. Strong motion records from both earthquakes and their impacts on structures as well as geotechnical issues are studied in this paper. Extensive liquefaction triggered lateral spread, landslide and slope failure cases were observed mainly at non-residential areas. Soil amplification is evaluated to be one of the main reasons for the heavy damage occurred in Ercis. Furthermore, site investigations and damage assessment performed after each earthquake proved that the observed damages are strongly correlated with insufficient qualities of structural materials, inadequate detailing and poor workmanship.