MPS Seminar: Imaging the Earth from sedimentary basins to the deep mantle (A. Fichtner)

Complex interactions of small- and large-scale processes are characteristic for the physics of the Earth, and their proper quantification is key to the integration of interdependent geophysical systems that are today mostly treated as isolated.Inferring Earth structure over a wide range of scales is the long-standing goal of seismic tomography. While much progress has been made in recent years, the following challenges still seriously limit tomographic resolution: (1) the limited data coverage that results from the irregular distribution of sources and receivers, (2) the consistent integration of small- and large-scale features into one tomographic model, and (3) our inability to assess uncertainties quantitatively and efficiently.To address these challenges, we developed a multi-scale full waveform inversion that assimilates complete teleseismic and regional seismograms in a broad frequency band from 1/200 to 1/8 Hz. Being based on spectral-element modelling and adjoint techniques, our method simultaneously solves multiple regional- and continental-scale inverse problems in order to jointly resolve Earth structure with resolving lengths ranging from around 10 to more than 5000 km. Different scales are coupled via non-periodic homogenisation, and tomographic resolution is quantified using a random probing technique of the Hessian.We apply our method to Europe and Western Asia, where resolution is particularly high beneath the North Atlantic, the western Mediterranean and Anatolia. The multitude of geologically interpretable features extend from the shallow surface into the deep mantle. They include the Iceland-Jan Mayen plume system, the lithospheric expression of the North Anatolian Fault Zone, the morphology of subducting lithospheric slabs beneath the western Mediterranean region, as well as the Rhone, Po, Molasse and Ebro basins.The extension of our approach to the globe is the backbone of an emerging Comprehensive Seismic Earth Model that assimilates the complete range of seismic data into one consistent model of the Earth’s interior by combining various tomographic techniques, including full waveform inversion, ray tomography, and normal-mode inversion.