Preprints
https://doi.org/10.5194/nhess-2022-196
https://doi.org/10.5194/nhess-2022-196
 
12 Jul 2022
12 Jul 2022
Status: this preprint is currently under review for the journal NHESS.

The OBS noise due to deep ocean currents

Carlos Corela1, Afonso Loureiro1, José Luis Duarte1, Luis Matias1, Tiago Rebelo2, and Tiago Bartolomeu2 Carlos Corela et al.
  • 1Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
  • 2CEIIA, Av. D. Afonso Henriques, 1825, 4450-017 Matosinhos, Portugal

Abstract. Ocean bottom seismometers (OBS) are usually deployed for seismological investigations but these objectives are impaired by noise resulting from ocean environment. We split the OBS recorded seismic noise into three domains, short-period, microseisms and long-period, also known as tilt-noise. We show that the first and third domains are controlled by bottom currents but these are not always a function of the tidal forcing. Instead we suggest that the ocean bottom has a flow regime resulting from two possible contributions, the permanent low frequency bottom current and the tidal current. The recorded noise displays the balance between these two currents along the full tidal cycle, between neap and spring tides. In the short-period noise band the ocean current generates harmonic tremors that corrupt the dataset records. We show that, in the analyzed cases, the harmonic tremors result from the interaction between the ocean current and mechanical elements of the OBS that are not essential for sea bottom recording and thus have no geological origin. The data from a new Broadband OBS type, designed and built at Instituto Dom Luiz (University of Lisbon)/CEIIA, hiding no essential components from current flow, shows how utmost of the harmonic noise can be eliminated.

Carlos Corela et al.

Status: open (until 28 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-196', Wolfram Geissler, 30 Jul 2022 reply

Carlos Corela et al.

Carlos Corela et al.

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Short summary
We show that ocean bottom seismometers are controlled by bottom currents but these are not always a function of the tidal forcing. Instead we suggest that the ocean bottom has a flow regime resulting from two possible contributions, the permanent low frequency bottom current and the tidal current along the full tidal cycle, between neap and spring tides. In the short-period noise band the ocean current generates harmonic tremors that corrupt the dataset records.
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