Upper crustal Poisson’s ratio and coda-wave attenuation beneath Eastern Anatolia

Abstract

The attenuation of seismic waves reflects the elastic nature of the media within which the waves propagate. In this study, we calculate the Coda-Q (Qc), frequency dependence (η), Vp/Vs and Poisson’s (υ) ratios by using 2621 vertical component seismograms generated by 987 earthquakes recorded by 13 seismic stations in Eastern Anatolia, and creat a 2-D seismic tomographic Qc model for the region. The obtained model provides significant information for exploring the boundaries of adjacent tectonic units within the upper crust and interpreting their dynamic characteristics. The 2-D Qc model and the other parameters are consistent with the seismotectonic features of Eastern Anatolia. Highly heterogeneous Qc values are observed in the study area dividing it into north-south directed bands of low and high attenuation. The highest η values were obtained beneath the northwestern and eastern parts of the study region. Clear, high and low υ values are obtained in the western and eastern parts of the study area, respectively. The spatial variations in the measured parameters are consistent with many geophysical observations including low Pn velocities, efficient Sn blockage, high heat flow, and widespread volcanism. Different upper crustal thicknesses and inhomogeneous stress distribution along the East and North Anatolian Fault Zones may also contribute to the observed heterogeneities. © 2020, Institute of Engineering Mechanics, China Earthquake Administration.