Crustal and upper mantle structure of the Eastern Anatolian Plateau using a new approach to the joint inversion of surface waves and receiver functions

Abstract:

Eastern Anatolia is characterized by the continent-continent collision of the Arabian and Eurasian Plates and the westward extrusion of the Anatolian Plate away from the collision zone. We investigate the effects of this deformation on the lithospheric structure of the collision zone using a new approach to the joint inversion of surface wave dispersion data and P-wave receiver functions. As opposed to traditional joint inversion methodologies that rely heavily on mathematical interpolation to constrain shear wave velocities between stations, our approach utilizes receiver functions derived from CCP stacking analysis. By spatially binning the receiver functions, we work to alleviate the dependence of shear wave velocity profiles on station distribution, leading to a data-driven shear wave velocity model at the resolution of the CCP stacking analysis.

We observe slow seismic velocities near the Karliova Triple Junction that correlate well with regions of high heat flow and moderate strain rates calculated from the inversion of GPS data. We propose that these are characteristics of a crust that has been rheologically weakened by continued deformation from the Arabia-Eurasia collision, which has allowed for the upward propagation of magma and the deposition of Miocene to recent volcanics on the surface. Seismically fast lithosphere is observed in east-central Anatolia and in the Arabian Plate and correlates with regions of low strain rates, implying the presence of rigid blocks. These rigid blocks are separated by a band of slow seismic velocities associated with the East Anatolian Fault Zone and consistent with the presence of fluids in the fault zone inferred from magnetotelluric studies. West of Lake Van, we find an anomalously shallow fast shear wave velocity anomaly that reaches 4.2 km/s, consistent with the seismic velocities in the uppermost mantle beneath Anatolia. We propose that this anomaly may represent a localized wedge of Eurasian mantle that was underthrust by Arabian continental lithosphere and uplifted during the break-off of the Arabian oceanic lithosphere around 11 Ma, coinciding with the highest exhumation rates in the Bitlis Massif.