Ambient noise correlation analysis of S-net records: Extracting surface wave signals below instrument noise levels

Ryota Takagi, Genti Toyokuni, Naotaka Chikasada

Research output: Contribution to journalArticlepeer-review

Abstract

We applied ambient noise cross-correlation analysis to the cabled ocean bottom seismic network offshore northeast Japan (Seafloor observation network for earthquakes and tsunamis along the Japan Trench: S-net) to extract surface waves propagating in the ocean area of the forearc region.We found two types of peculiar pulses in the cross-correlation functions (CCFs) of ambient seismic noise records: periodic pulsesmainly every minute and sharp pulses around the lag time zero. These pulses strongly contaminate the surface wave signals in the CCFs at frequencies below ~0.1 Hz. The periodic pulses originate from periodic instrument noises, while the zero-lag pulses originate from random instrument noises which are coherent within station pairs. By developing solutions to remove the periodic and zero-lag pulses based on the characteristics of the pulses, we succeeded in extracting Rayleigh and Love wave signals from the S-net records at 0.03-0.3 Hz, while the surface wave signals at 0.03-0.1 Hz were not visible without the application of these solutions. These solutions widen the frequency range of analysis, and may be applicable to other seismic networks, particularly to recent dense but non-broad-band networks. We identified the fundamental and first higher modes of Rayleigh waves and the fundamental mode of the Love wave. The extracted surface wave signals can constrain the shear wave velocity structure from the sediment to seismogenic zone around the megathrust plate boundary in the forearc region.

Original languageEnglish
Pages (from-to)1640-1657
Number of pages18
JournalGeophysical Journal International
Volume224
Issue number3
DOIs
Publication statusPublished - 2021 Mar 1

Keywords

  • Instrumental noise
  • Seismic interferometry
  • Seismic noise
  • Surface waves and free oscillations
  • Wave propagation

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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