Lithospheric Seismic Structure of the Anatolian Plate and Its Implications for Plateau Uplift: Evidence From Joint Inversion of Receiver Functions and Surface Waves

Abstract

High topography ($>$1 km) on the Anatolian Plate is widely attributed to buoyant mantle support, not just the isostatic response of crustal shortening. However, uncertainties in lithospheric structure hinder attempts to discriminate between competing uplift mechanisms. We jointly inverted receiver functions with Rayleigh wave group-velocity dispersion curves to obtain 1D shear velocity profiles for 575 seismograph stations across Anatolia. Crustal thickness increases from $\sim$25 km in the west to $\le$44 km below Eastern Anatolia, with short length-scale Moho topography in places. Within the Central Anatolian Plateau (CAP), thicker crust, lower residual topography, higher residual Bouguer gravity anomalies, and faster upper-mantle wavespeeds north of $\sim 39°$N than to the south suggest that northern CAP lithospheric removal is less-developed. Processes like slab break-off, lithospheric delamination and/or dripping are therefore more likely to contribute to the uplift in the south, with additional support from buoyant mantle flow through the Cyprus slab tear. A $\sim$5 km Moho step across the Eastern Anatolian Fault (EAF) results partly from dominant crustal shortening on the Anatolian Plate. Further east, no Moho depth contrast exists across the Bitlis suture; Arabia-Eurasia crustal shortening has thus been accommodated by both plates. An ENE–WSW-trending band of positive residual topography and negative residual Bouguer anomalies parallels the EAF below the northwestern tip of Arabia. This connects to a zone of peak residual topography and slow uppermost mantle wavespeeds below the magmatically active Eastern Anatolian Plateau. These observations are explained best by NE-flowing, buoyant mantle plume material from the Afar hotspot to the south.