Lateral structural variations of Poisson's ratio and attenuation coefficient in the upper crust of eastern and south-eastern Anatolia

In this study, lateral 2D Poisson's ratio and local attenuation coefficient changes have been examined using the 2473 digital earthquake data of eastern and south-eastern Turkey. Data used for this work came from the seismic records of events recorded by the stations of the Boĝazici University Kandilli Observatory and Earthquake Research Institute (KOERI) as well as the Ataturk University Earthquake Research Centre (AUERC). The method used in this study was based on 2D Poisson's ratio calculated from P- and S- velocity values and epicentre distance-amplitude attenuation coefficient methods. The estimated Poisson's ratio values for the 17 stations ranged from 0.142 to 0.309. Attenuation coefficient ratios were found to be between 1.072 and 1.362, with an average of 1.226. P- and S- wave velocity values for eastern and south-eastern Anatolia were determined as 6.317 and 3.608 km/s, respectively. These values were obtained from earthquake data with epicentre distances ranging from 15 to 184 km and focus depths ranging from 1.3 to 11.2 km. The lowest attenuation coefficients were obtained at the URFA station, while the highest attenuation coefficient values were observed at the SIRT and MALT stations. High σ values were observed in the northern part of the study area and SW of the Bitlis-Zagros thrust belt, whereas the lowest σ values were obtained at the Karliova triple junction and its surroundings. This study shows that different tectonic structures and actively deformed systems can be described by dynamic parameters such as local attenuation values and Poisson's ratio of the near-upper Earth crust.