3D shear wave velocity model of the crust and uppermost mantle beneath the Tyrrhenian basin and margins

D Manu-Marfo,R Kherchouche,A Aoudia,S Pachhai

doi:10.1038/s41598-019-40510-z

Abstract

The Tyrrhenian basin serves as a natural laboratory for back-arc basin studies in the Mediterranean region. Yet, little is known about the crust-uppermost mantle structure beneath the basin and its margins. Here, we present a new 3D shear-wave velocity model and Moho topography map for the Tyrrhenian basin and its margins using ambient noise cross-correlations. We apply a self-parameterized Bayesian inversion of Rayleigh group and phase velocity dispersions to estimate the lateral variation of shear velocity and its uncertainty as a function of depth (down to 100 km). Results reveal the presence of a broad low velocity zone between 40 and 80 km depth affecting much of the Tyrrhenian basin’s uppermost mantle structure and its extension mimics the paleogeographic reconstruction of the Calabrian arc in time. We interpret the low-velocity structure as the possible source of Mid-Ocean Ridge Basalts- and Ocean Island Basalts- type magmatic rocks found in the southern Tyrrhenian basin. At crustal depths, our results support an exhumed mantle basement rather than an oceanic basement below the Vavilov basin. The 3D crust-uppermost mantle structure supports a present-day geodynamics with a predominant Africa-Eurasia convergence.

Highlights

The Tyrrhenian basin serves as a natural laboratory for back-arc basin studies in the Mediterranean region
The tomography maps at short periods (5–10 s, Fig. 2a,b,i,j) show pronounced high-velocity anomalies in the southern Tyrrhenian basin, which likely indicates the presence of a high velocity material at shallow depth
A noteworthy observation is that the boundary between the north and south anomalies approximately coincides with the 41° Parallel Line which is generally considered as the divide between the northern and southern Tyrrhenian basin

Summary

Introduction

The Tyrrhenian basin serves as a natural laboratory for back-arc basin studies in the Mediterranean region. Little is known about the crust-uppermost mantle structure beneath the basin and its margins. The problem with active seismological studies is that it provides very little information about the lithospheric structure beneath the Moho and yields relatively limited information on the lateral variation of the velocity structure. Difficulties in achieving high-resolution images of the lithosphere using data from ‘traditional’ seismic imaging techniques[18,19] This method has been already applied in the Tyrrhenian area[20,21,22,23], but in the framework of regional studies covering the whole Europe[20,21,22] or the Italian peninsula[23] and does not provide much detailed structure beneath the Tyrrhenian basin

Results

Discussion

Conclusion