Detecting Active Faults Using Electrical Resistivity Tomography: a Case Study in Istanbul, Türkiye

relatively far (over 100 km) from the epicenter of the 17 August 1999 & Idot;zmit earthquake, the Istanbul/Avc & imath;lar region suffered unexpected severe damage to many buildings and some casualties. Since future earthquakes in this highly populated region are expected in the following decades, it is crucial to assess the seismic risk to develop mitigation strategies. Critical faults in the sea of the study area were mentioned in previous studies, and their possible connections were mentioned, but a dataset showing their connections was not presented. To investigate this aspect further, we performed a geo-electrical survey around K & uuml;& ccedil;& uuml;k & ccedil;ekmece Lake, which included 14 inverted vertical electrical soundings (VESs) to provide resistivity vs depth sections. We also collected three 2D electrical resistivity tomography (ERT) data profiles. The ERT and inverted VES data show that a network of faults cut the most recent sedimentary units, causing sharp resistivity changes. In this study, land faults for the city of Istanbul were shown for the first time through geophysical studies. Because this area lies off the principal displacement zone of the North Anatolian Fault in this region, such features could represent the reactivation of old tectonic structures. However, we stress that the peculiar geological setting of the Istanbul/Avc & imath;lar region should be considered when evaluating seismic scenarios given that a future earthquake will affect the Istanbul metropolitan area.