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Abstract

With amplitude and full-waveform based ambient noise tomography and monitoring methods on the horizon, knowledge of the underlying noise source distribution is vital to avoid possible misinterpretations, e.g., in terms of time-varying Earth structure. Particularly the oceanic microseisms have strong spatio-temporal variations on multiple scales which could influence full waveform or travel time measurements if not taken into account properly. In this work, we present daily Seismic Ambient Noise Source (SANS) maps of the secondary microseisms (0.1 to 0.2 Hz) on a global scale which are made available to the public here: sans.ethz.ch (Igel et al., 2022). The computation of daily global SANS maps is possible due to recent improvements of non-linear finite-frequency noise source inversion methodology including pre-computed wavefields and spatially variable grids (Igel et al., 2021). Furthermore, by introducing an initial model from a different noise source imaging method - Matched Field Processing (MFP) - we accelerate the convergence of the inversion and improve the final maps. In collaboration with the Swiss National Supercomputing Centre (CSCS), we are able to run daily global SANS inversions which can be viewed, downloaded, and implemented into other studies. This paves the way for future full waveform ambient noise source and structure inversion workflows.