Comprehensive Lithospheric Structure of France: Joint Inversion of Seismic, Gravity, and Gradiometry Data

We present a comprehensive model of lithospheric structure extending to 300 km beneath France, derived from a joint inversion of teleseismic, gravity, and gradiometry datasets. Our analysis incorporates 27,935 relative travel time residuals sourced from the 193 French permanent seismic stations (EPOS-France), alongside 30,351 terrestrial gravity measurements and the complete gravity gradient tensor from GOCE satellite mission. The integration of these three complementary datasets enhances our understanding of lithospheric structures. Our joint inversion method allows for inverting the velocity-density relationship with independent model parametrization.

Through the velocity model, our findings reveal significant lateral variations in P-wave velocity, including a prominent orogen-parallel high-velocity anomaly that extends from the surface to a depth of 135 km, centered beneath the Pyrenees and the Southern Alps. Additionally, we identify a high-velocity body extending from the surface down to 80 km beneath the Massif Central. Notably, our density model highlights several key features, including a narrow high-density body between 10 and 40 km depth, known as the Ivrea body in the Alps. Our results are to compare with previous regional temporary inversions, especially for the northern Pyrenees where velocity and density models are not always coherent. These results contribute to a more nuanced understanding of the lithospheric dynamics in this geologically complex region.