A reconnaissance study in Izmir (Bornova Plain) affected by October 30, 2020 Samos earthquake

Abstract

On October 30th of 2020, 14:51 (GMT+3:00), Izmir city was hit by an earthquake of Mw = 7.0 magnitude (according to USGS). A rupture of 30-40 km of a west-east normal fault, which is roughly 12 km north to Samos Island caused significant damage, particularly in Izmir (Bornova plain). This study aims to present the preliminary field investigations, evaluation of structural damage as well as the possible geotechnical phenomenon affecting the damage that occurred. In this context, an extensive analysis of spectral characteristics of the earthquake and local site effects is presented. Field investigations reveal that there is a significant amplification of the rock acceleration along with a basin effect in the region, which results in a wider constant acceleration region. In addition, analysis of earthquake records shows a remarkable level of soil nonlinearity. Considering all these aspects, a detailed assessment of structural damage observed in Izmir Bayrakli District is presented. It is evident that, structures of poor construction details behaved as if they were affected by a near field earthquake. The structures to be constructed in alluvial zones such as Manavkuyu neighborhood should be designed considering the effects of soil amplification including basin effects and soil nonlinearity. To fulfill this aim, comparative results of 1D/2D/3D ground response analyses should be performed, for revising current earthquake codes.