Coherence-based imaging and inversion on large-scale seismic arrays

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The detailed knowledge of the structure and constituents of the Earth's subsurface allows for many important applications, ranging from risk assessments on engineering sites near the surface to the exploration of geothermal or hydrocarbon reservoirs to meet energy demands and answering fundamental geodynamical questions on continental or even global scales. Using either the natural seismicity of earthquakes or artificially excited controlled sources, the seismic method proved to be an essential tool for all these problems. While in the global regime of earthquake seismology, however, the tomographic inversion of subsurface properties like seismic velocities has played the central role, the industry-driven local seismology of controlled sources in hydrocarbon exploration for a long time had the main goal of a sharpest possible structural image by focusing the backscattered, i.e. reflected or diffracted portion of the wavefield. With the advent of full-waveform inversion and the installation of receiver networks that span large regions of the Earth's surface, technical developments in these fields begin to naturally approach each other. Besides the inversion of full waveforms, the rapid growth of current large-scale seismic arrays suggests applications of imaging schemes, which, similar to reservoir exploration, may lead to a richer, complementary picture of the still vaguely known structure of the Earth's mantle and core. While first promising results have been obtained in recent years using conventional seismic depth imaging techniques, the aim of this project is to make the maximum use of the increasing redundancy in the data acquired in earthquake seismology. By adapting a cutting-edge data-driven stacking scheme from industrial seismic exploration, I aim at complementing and supporting the established approach of broadband tomography with large-scale structural images of the deeper interior for the very recently completed densely acquiring USarray campaign in North America, promising interesting implications for future workflows in both fields.