Estimation of Coda Q Wave Attenuation Factors for Northern Iraq

Abstract

The coda wave decay method was used to estimate the quality factor from the coda wave amplitude decay rate for the broadband seismic stations in northern Iraq using a single back-scattering model. The study aims to calculate the attenuation factor to comprehend the details of the structure of the earth's crust in the study area. The study was conducted using data from the Mesopotamian Network and the Iraqi Meteorological Organization and Seismology from 2007 to 2021. The selected earthquakes have magnitudes ranging from 4 to 6.1 ML and epicentral distances of less than < 100 km. Seventy seven earthquakes were recorded by three stations (SLY1, DHK1, and IKRK). These earthquakes were analyzed at eight center frequencies (1, 2, 3.5, 6, 8, 10, 12, and 16 Hz) and a 30-sec length window by using the Seisan package. The Qc values are computed by the frequency-dependent relationship QC= Q0 f α, where Q0 is QC at 1 Hz and α denotes the degree of frequency dependence. The attenuation relationship of station SLY1 is obtained as QC =88 f 1.02, QC = 90 f 0.97 in the DHK1 station, and QC = 91 f 1.04 in the IKRK station. The comparison of these three stations indicates that attenuation is highest in Sulaymaniyah, followed by Duhok, and then Kirkuk.