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SANS: Publicly Available Daily Multi-Scale Seismic Ambient Noise Source Maps
  • Jonas Karl Hans Igel,
  • Daniel C. Bowden,
  • Andreas Fichtner
Jonas Karl Hans Igel
ETH Zurich

Corresponding Author:[email protected]

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Daniel C. Bowden
ETH Zürich
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Andreas Fichtner
ETH Zurich
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Seismic ambient noise sources have received increased attention recently, creating new possibilities to study the Earth’s subsurface and the atmosphere-ocean-solid Earth coupling. In efforts to locate such noise sources using nonlinear finite-frequency inversions, methodological developments such as pre-computed wavefields and spatially variable grids were necessary. These make inversions feasible for the secondary microseismic sources in a frequency range up to 0.2 Hz on a daily basis. By obtaining a starting model for the inversion using Matched Field Processing (MFP) we are able to further steer the inversion towards acceptable global noise source models and improve the final result. Analysis of one year of daily inversions shows the seasonal variations of the secondary microseisms and their dependence on the atmosphere-ocean-solid Earth coupling due to storm-induced ocean waves. We present a web framework, SANS (Seismic Ambient Noise Sources, sans.ethz.ch), where daily regional- to global-scale seismic ambient noise source maps are made available to the public. This eases the implementation of time-variable noise source distributions into full-waveform ambient noise tomography and time-dependent subsurface monitoring methods. Additionally, it encourages other studies to verify if changes in the seismic data are due to changes in the subsurface velocity or spatio-temporal variations of noise sources.