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Sediment structure at the equatorial mid-atlantic ridge constrained by seafloor admittance using data from the PI-LAB experiment

Sediment structure at the equatorial mid-atlantic ridge constrained by seafloor admittance using data from the PI-LAB experiment
Sediment structure at the equatorial mid-atlantic ridge constrained by seafloor admittance using data from the PI-LAB experiment
Well-constrained marine sediment characteristics (sediment thickness and shear wave velocity) are important not only for the study of climate over geologic times scales but also for correcting and accounting for its presence in seismic data used to investigate deeper structures. We use data from the PI-LAB (Passive Imaging of the Lithosphere Asthenosphere Boundary) experiment, which consisted of 39 broadband ocean bottom seismometers deployed at the Equatorial Mid-Atlantic Ridge near the Chain fracture zone covering 0–80 Myr old seafloor. We compute admittance between the pressure to the vertical displacement at the seafloor at frequencies between 0.1 and 0.2 Hz for microseism-generated Rayleigh waves for 18 stations where data quality is good to determine the sediment thickness and shear wave velocity. We find a general trend of increasing sediment thickness with the seafloor ages, as expected with sediment thicknesses that range from 10–450 m and, shear wave velocities that range from 0.05–0.34 km/s. We find sediment thickness varies almost uniformly across both sides of the ridge, and it indicates that both sides experienced a similar sedimentation process. Our results are in good agreement with the global sediment model that is based on drilling cores and active source experiments, but thinner by up to 50 m at several stations on seafloor older than 25 My. Overlap of the 95% confidence regions between admittance and Ps estimates for thickness and shear velocity is found at 15 stations where we have both Ps and admittance estimates. It suggests that both methods yield accurate estimates for sediment thickness. In addition, our admittance result extends the lateral resolution of sediment characteristics to stations that were not previously resolved by Ps.
Admittance function, Ocean bottom seismometers, Sediment properties, Shear wave velocity
0025-3235
Saikia, Utpal
fdc84905-f84a-459f-b689-e22f5a642a02
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Kendall, Mike
49233af5-e888-4ab8-87b7-d97938f0ed27
Saikia, Utpal
fdc84905-f84a-459f-b689-e22f5a642a02
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Kendall, Mike
49233af5-e888-4ab8-87b7-d97938f0ed27

Saikia, Utpal, Rychert, Catherine, Harmon, Nicholas and Kendall, Mike (2020) Sediment structure at the equatorial mid-atlantic ridge constrained by seafloor admittance using data from the PI-LAB experiment. Marine Geophysical Researches, 41 (3), [3]. (doi:10.1007/s11001-020-09402-0).

Record type: Article

Abstract

Well-constrained marine sediment characteristics (sediment thickness and shear wave velocity) are important not only for the study of climate over geologic times scales but also for correcting and accounting for its presence in seismic data used to investigate deeper structures. We use data from the PI-LAB (Passive Imaging of the Lithosphere Asthenosphere Boundary) experiment, which consisted of 39 broadband ocean bottom seismometers deployed at the Equatorial Mid-Atlantic Ridge near the Chain fracture zone covering 0–80 Myr old seafloor. We compute admittance between the pressure to the vertical displacement at the seafloor at frequencies between 0.1 and 0.2 Hz for microseism-generated Rayleigh waves for 18 stations where data quality is good to determine the sediment thickness and shear wave velocity. We find a general trend of increasing sediment thickness with the seafloor ages, as expected with sediment thicknesses that range from 10–450 m and, shear wave velocities that range from 0.05–0.34 km/s. We find sediment thickness varies almost uniformly across both sides of the ridge, and it indicates that both sides experienced a similar sedimentation process. Our results are in good agreement with the global sediment model that is based on drilling cores and active source experiments, but thinner by up to 50 m at several stations on seafloor older than 25 My. Overlap of the 95% confidence regions between admittance and Ps estimates for thickness and shear velocity is found at 15 stations where we have both Ps and admittance estimates. It suggests that both methods yield accurate estimates for sediment thickness. In addition, our admittance result extends the lateral resolution of sediment characteristics to stations that were not previously resolved by Ps.

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Accepted/In Press date: 26 January 2020
e-pub ahead of print date: 15 February 2020
Keywords: Admittance function, Ocean bottom seismometers, Sediment properties, Shear wave velocity

Identifiers

Local EPrints ID: 439388
URI: http://eprints.soton.ac.uk/id/eprint/439388
ISSN: 0025-3235
PURE UUID: 6fa57fe3-1ee3-496e-89fb-5f268a91dc78
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X

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Date deposited: 21 Apr 2020 16:30
Last modified: 18 Feb 2021 17:13

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