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The effect of methane hydrate morphology and water saturation on seismic wave attenuation in sand under shallow sub-seafloor conditions

The effect of methane hydrate morphology and water saturation on seismic wave attenuation in sand under shallow sub-seafloor conditions
The effect of methane hydrate morphology and water saturation on seismic wave attenuation in sand under shallow sub-seafloor conditions
A better understanding of seismic wave attenuation in hydrate-bearing sediments is needed for the improved geophysical quantification of seafloor methane hydrates, important for climate change, geohazard and economic resource assessment. Hence, we conducted a series of small strain (<10?6), seismic frequency (50–550 Hz), laboratory resonant column experiments on synthetic methane hydrate-bearing sands under excess-water seafloor conditions. The results show a complex dependence of P- and S-wave attenuation on hydrate saturation and morphology. P- and S-wave attenuation in excess-water hydrate-bearing sand is much higher than in excess-gas hydrate-bearing sand and increases with hydrate saturation between 0 and 0.44 (the experimental range). Theoretical modelling suggests that load-bearing hydrate is an important cause of heightened attenuation for both P- and S-waves in gas and water saturated sands, while pore-filling hydrate also contributes significantly to P-wave attenuation in water saturated sands. A squirt flow attenuation mechanism, related to microporous hydrate and low aspect ratio pores at the interface between sand grains and hydrate, is thought to be responsible for the heightened levels of attenuation in hydrate-bearing sands at low hydrate saturations (<0.44).
seismic attenuation, hydrate, sediment, morphology
0012-821X
78-87
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Priest, Jeffrey A.
b075689b-0700-484f-b9a6-11b1211a9aab
Clayton, Christopher R.I.
8397d691-b35b-4d3f-a6d8-40678f233869
Rees, Emily V.L.
19e94514-d854-460e-ba1b-e6e1bc4157d4
Best, Angus I.
cad03726-10f8-4f90-a3ba-5031665234c9
Priest, Jeffrey A.
b075689b-0700-484f-b9a6-11b1211a9aab
Clayton, Christopher R.I.
8397d691-b35b-4d3f-a6d8-40678f233869
Rees, Emily V.L.
19e94514-d854-460e-ba1b-e6e1bc4157d4

Best, Angus I., Priest, Jeffrey A., Clayton, Christopher R.I. and Rees, Emily V.L. (2013) The effect of methane hydrate morphology and water saturation on seismic wave attenuation in sand under shallow sub-seafloor conditions. Earth and Planetary Science Letters, 368, 78-87. (doi:10.1016/j.epsl.2013.02.033).

Record type: Article

Abstract

A better understanding of seismic wave attenuation in hydrate-bearing sediments is needed for the improved geophysical quantification of seafloor methane hydrates, important for climate change, geohazard and economic resource assessment. Hence, we conducted a series of small strain (<10?6), seismic frequency (50–550 Hz), laboratory resonant column experiments on synthetic methane hydrate-bearing sands under excess-water seafloor conditions. The results show a complex dependence of P- and S-wave attenuation on hydrate saturation and morphology. P- and S-wave attenuation in excess-water hydrate-bearing sand is much higher than in excess-gas hydrate-bearing sand and increases with hydrate saturation between 0 and 0.44 (the experimental range). Theoretical modelling suggests that load-bearing hydrate is an important cause of heightened attenuation for both P- and S-waves in gas and water saturated sands, while pore-filling hydrate also contributes significantly to P-wave attenuation in water saturated sands. A squirt flow attenuation mechanism, related to microporous hydrate and low aspect ratio pores at the interface between sand grains and hydrate, is thought to be responsible for the heightened levels of attenuation in hydrate-bearing sands at low hydrate saturations (<0.44).

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Published date: 15 April 2013
Keywords: seismic attenuation, hydrate, sediment, morphology
Organisations: Marine Geoscience, Civil Maritime & Env. Eng & Sci Unit

Identifiers

Local EPrints ID: 353625
URI: https://eprints.soton.ac.uk/id/eprint/353625
ISSN: 0012-821X
PURE UUID: 64d90552-67f6-434c-8937-88a6406ef118
ORCID for Christopher R.I. Clayton: ORCID iD orcid.org/0000-0003-0071-8437

Catalogue record

Date deposited: 11 Jun 2013 15:55
Last modified: 31 Jul 2019 00:47

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