Field Investigation of the Performance of Unreinforced Masonry Building Structures during the June 12, 2017, Lesvos Earthquake in the Aegean Sea

On June 12, 2017, at 1528 local time (1228 GMT), an earthquake of magnitude MW=6.2 occurred, its epicenter in the Aegean Sea (south of Lesvos Island), approximately 23 km to the north of Izmir's district of Karaburun. The impact of the earthquake left structures in various states of damage, particularly in the town of Vrissa on Lesvos. The types of damage occurring in the buildings of stone masonry in the town of Vrissa, the damage mechanisms, levels of damage and causes of the damage, as well as the relationship between structural characteristics and damage mechanisms have been evaluated in this paper. It was seen in the field investigations that the heavily damaged, partially collapsed, and totally collapsed buildings were generally nonengineered structures. Additionally, the various limitations and dimensional requirements of the Turkish Earthquake Code had not been applied to the damaged masonry buildings in Vrissa. Lower levels of damage had been sustained in masonry buildings in the earthquakes recorded in Elazlǧ, Van, and Ayvaclk, where peak ground acceleration values of strong ground motions were even higher. This was mainly due to the structural characteristic of the houses of Vrissa that rendered a weak connection between the stone external walls and the internal separating walls of the orthogonal wooden construction on the upper floors. The length of the unsupported load-bearing stone external wall was over the limit specified by the Turkish Earthquake Code, which was the fundamental factor that increased the destructibility of the Vrissa houses.