EGU2020-20890
https://doi.org/10.5194/egusphere-egu2020-20890
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Sensitivity kernels for coda-wave interferometry in a three-dimensional scalar scattering media

Andres Barajas1, Ludovic Margerin2, and Michel Campillo3
Andres Barajas et al.
  • 1ISTerre, UGA, Grenoble, France (andres.barajas-ramirez@univ-grenoble-alpes.fr)
  • 2IRAP, Université de Toulouse, Toulouse, France ( Ludovic.Margerin@irap.omp.eu)
  • 3ISTerre, UGA, Grenoble, France (michel.campillo@univ-grenoble-alpes.fr)

The ambient seismic noise has proven to be a powerful tool to assess velocity changes within the ground using coda-wave interferometry (CWI). CWI is based on the analysis of small waveform changes in the coda of the signals. Localizing and imaging the source that generates changes can be done with the help of sensitivity kernels which contain information on how each part of the surrounding medium contributes to the overall waveform perturbation that is recorded at a receiver. Although progress has been made in the theory of sensitivity kernels in the case of a full elastic space,  the inclusion of a free surface has proven to be difficult. Indeed, the free surface couples body waves and surface waves, which affects the sensitivity of coda waves with respect to the full-space case. Furthermore, one expects the depth sensitivity of coda waves to be strongly dependent on the relative contribution of surface and body waves, which depends on the lapse-time, source-receiver distance and scattering properties of the medium. Using the Monte-Carlo method, we compute traveltime-sensitivity kernels in a 3D scalar problem that includes body and surface waves, based on a recent theoretical model that integrates both through a mixed boundary condition. From these results, we assess the impact of the depth of a velocity perturbation on the recorded signals at the surface. Our results will be compared with previous numerical approaches from the literature. 

How to cite: Barajas, A., Margerin, L., and Campillo, M.: Sensitivity kernels for coda-wave interferometry in a three-dimensional scalar scattering media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20890, https://doi.org/10.5194/egusphere-egu2020-20890, 2020

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Presentation version 1 – uploaded on 03 May 2020
  • CC1: Comment on EGU2020-20890, Eric Larose, 05 May 2020

    Hello, nice work !

    do you think there is a way to include some kind of (bulk) refraction and/or take into account multiple bulk reflection at the surface ?

    • AC1: Reply to CC1, Andres Barajas, 05 May 2020

      Hi, thanks!

      The presented results are based on the scattering properties of the medium, and such, they account for possible (multiple) changes of direction of the particles. This includes the possibility of changing the mean free paths or to add spatial dependence to them (as the case of the depth-dependent body wave means free path in this work).

      The simulation takes into account also the reflection of the body energy at the surface

      I hope this answers your question!