EGU2020-481, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-481
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Simultaneous body and surface wave retrieval from the seismic ambient field and discrimination from unavoidably arising spurious artifacts

Ali Riahi1, Zaher-Hossein Shomali2,3, Anne Obermann4, and Ahmad Kamayestani5
Ali Riahi et al.
  • 1Institute of Geophysics of University of Tehran (IGUT), University of Tehran , Iran (ali.riahi@ut.ac.ir)
  • 2Institute of Geophysics of University of Tehran (IGUT), University of Tehran , Iran (shomali@ut.ac.ir)
  • 3Department of Earth Sciences, Uppsala University, Sweden (Hossein.Shomali@geo.uu.se)
  • 4Swiss Seismological Service (SED), ETH Zurich, Switzerland (anne.obermann@sed.ethz.ch)
  • 5Department of Geophysics, National Iranian Oil Company- Exploration Directorate, Iran (a.kamayestani@niocexp.ir)

We simultaneously extract both, direct P-waves and Rayleigh waves, from the seismic ambient noise field recorded by a dense seismic network in Iran. With synthetics, we show that the simultaneous retrieval of body and surface waves from seismic ambient noise leads to the unavoidable appearance of spurious arrivals that could lead to misinterpretations.

We work with 2 months of seismic ambient noise records from a dense deployment of 119 sensors with interstation distances of 2 km in Iran. To retrieve body and surface waves, we calculate the cross-coherency in low-frequency ranges, i.e. frequencies up to 1.2 Hz, to provide the empirical Green’s functions between each pair of stations. To separate the P and Rayleigh waves, we use the polarization method that also enhances the small amplitude body waves.

We observe both P and Rayleigh waves with an apparent velocity of 4.9±0.3 and 1.8±0.1 km/s in the studied area, respectively, as well as S or higher mode of Rayleigh waves, with an apparent velocity of 4.1±0.1 km/s. Besides these physical arrivals, we also observe two spurious arrivals with similar amplitudes before/after the P and/or Rayleigh waves that render the discrimination challenging.

To better understanding these arrivals, we perform synthetic tests. We show that simultaneously retrieving the body and surface waves from seismic ambient noise sources will unavoidably lead to the appearance of superior arrivals in the calculation of empirical Green’s functions.

How to cite: Riahi, A., Shomali, Z.-H., Obermann, A., and Kamayestani, A.: Simultaneous body and surface wave retrieval from the seismic ambient field and discrimination from unavoidably arising spurious artifacts, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-481, https://doi.org/10.5194/egusphere-egu2020-481, 2019

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