Structural evaluation of masonry building damages during the April 24, 2014 Gökçeada earthquake in the Aegean Sea

An earthquake of M_W = 6.5 occurred on May 24, 2014, at 12:25 h local time (09:25 GMT), its epicenter in the Aegean Sea, 25 km north of Gökçeada. The effect of the earthquake produced the most damage in the rural houses of Gökçeada. This paper describes the evaluations made through onsite field observations of the damages inflicted on the structures of thirty rural houses in the Tepeköy settlement connected to Gökçeada. An evaluation was made of the types of damage, the mechanisms of damage and the causes of the damage sustained by these houses, which all had similar structural characteristics but different plan typologies and suffered varying levels of damage. The damage observed in Gökçeada was classified using the catalogue of mechanisms originally developed for the failure mechanisms identification and vulnerability evaluation procedure. The general types of damage were cracks in the loadbearing external walls and corners, diagonal cracks starting from the corners of doors and windows, vertical out-of-plane displacement of external walls, out-of-plane fragmentation or disintegration and collapse of external wall and partial collapse of loadbearing internal walls, ruptures in the outer surfaces of loadbearing external walls, partial collapse of roof structure, partial collapse of hearth and chimney sections, rupture or flaking of window and door lintels. The causes of the general damage may be cited as an irregular bonding system, weak mortar, stone block formation, stone block size, absence of tie beams, corners weakly connected, weak connection of wall-roof system, week connection of wall-floor system, and different internal wall systems. The levels of damage and the mechanisms of damage vary depending upon the number of causes of the damage, the particulars of the layout, and some structural properties. In terms of the characteristics of the layout, an increase in unsupported loadbearing wall lengths led to more destructive damage mechanisms in the houses. In terms of structural characteristics, the construction of the internal wall system with timber on the upper floors, and with stone material on the lower floors was a major factor in increasing the level of damage and determining its type and mechanism.