Crustal Features of Eastern Anatolia based on a Joint Grid Search Performed over Receiver Functions and P-wave Coda Autocorrelation

Abstract

The complex tectonic structure of eastern Anatolia results from the superposition of subduction and collisional structures along a long-lived convergent margin between the Gondwanan (Arabian) and Eurasian plates. The geodynamic processes shaping the tectonic setting and uplifting history of the region still remain enigmatic despite the fact that the number of geophysical, geological, and petrographic-based models/interpretations in recent years has increased notably. Further issues, i.e., how the spatiotemporal patterns of seismic activity are controlled by pre-existing deformational zones in the lithosphere and/or modern convergent stresses, and how magmatism is related to the lithospheric variability along the margin, are unclear. Models of seismological features of the Earth’s interiors provide insights on isotropic heterogeneity that are of great importance for constraining the current physical and chemical conditions, as they likely control the localization of structures. For this purpose, the present study aims to constrain lateral variations of crustal thickness, Moho topography, and average seismic velocities (Vp, Vp/Vs) by leveraging information from both teleseismic scattered (receiver function) and reflected (autocorrelation) waves (H-k-Vp stacking). Incorporating teleseismic autocorrelation waveforms from the P-wave coda, we can better constrain average crustal P-wave velocities (Vp) by highlighting the amplitude term of the Moho-reflected Pmp phase. Our dataset consists of digital waveforms extracted from 512 teleseismic events (within the epicentral distance range from 30° to100° and with Mw>6) observed at 33 permanent broadband seismic stations operated under the KOERI network between 2013 and 2022 and will result in a new map of crustal architecture and its physical properties (crustal thickness, Vp, and Vp/Vs) below eastern Anatolia. Preliminary results indicate a thickening crust from south to north reaching down to depths of ~50 km. High Vp/Vs ratios mark volcanic provinces as well as fault damage areas presumably characterized by highly fractured rocks with high amounts of water content. Lateral variations of P-wave velocities along two continental fault zones (EAFZ and NAFZ) of the region imply that the degree of shear deformation and resultant seismic activity is well-correlated with density/seismic wave speed variations. Moho depth variations across the NAFZ further suggest a much narrow and localized distribution of deformation in the lower crust and upper mantle compared to the EAFZ. Further analysis of these results will lead to a better understanding of the controlling mechanisms behind seismicity and magmatism in the Eastern Anatolian Plateau.