Determination of Coda Wave attenuation characteristic of the Armutlu Peninsula and its surroundings (Middle Marmara Region, Turkey).

Abstract

The Armutlu Peninsula, is located in a geologically complex system on the North Anatolian Fault Zone and inside the high populated Mar- mara Region. Due to its location and importance, the Marmara Region has been subject to various studies in the past; now, this study is aimed to determine the local attenuation characteristic of the Armutlu Peninsula. In this study, 75 earthquake data that were recorded between 2013- 2014, were analyzed by 9 seismic stations. The magnitudes (Ml) and the focal depths of the earthquakes vary from 1.5 to 3.3 and 0.9 to 16.9 km, respectively. A single back-scattering model was used for calculation of the coda wave quality factor. The lapse times were determined between 20 and 40 s at intervals of 5 s and they were filtered at central frequencies of 1.5, 3, 6, 9 and 12 Hz band-pass designed filter. Min- imum 5 signal/noise ratio and 0.7 correlation coefficient data used to obtain reliable results. The CODAQ subroutine integrated in the SEISAN software was used for data processing. For each station, low values of the quality factor at 1 Hz (Qo) and high values of the frequency de- pendent parameter (n) were determined. In the Armutlu Peninsula and its surroundings, Qc=51f0.91 for 20 s and Qc=112f0.72 for 40 s window lengths were calculated by using 9 stations. There is a tendency between increasing Qo and decreasing n parameters. Otherwise, for station TRML, located near the geothermal hotspot, these parameters are in direct proportion with each other, as Qc=46f0.97 for 20 s and Qc=74f1.06 for 40 s window lengths. These parameter changes are directly connected with the geothermal activity.