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Updip rupture of the 2004 Sumatra earthquake extended by thick indurated sediments

Updip rupture of the 2004 Sumatra earthquake extended by thick indurated sediments
Updip rupture of the 2004 Sumatra earthquake extended by thick indurated sediments
During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulate near the subduction trench axis. The weak nature of the sediments usually impedes the propagation of fault rupture during an earthquake. However, measurements of slip during the 2004 Sumatra–Andaman Mw 9.2 earthquake show that fault rupture propagatedupdip, extending unusually close to the subduction trench, in the southern part of the rupture area. Here we present seismic reflection images of the southern part of the 2004 Sumatra–Andaman earthquake rupture area. We show that sedimentary strata, greater than 4?km in thickness, form coherent blocks that have been thrust onto the continental margin during subduction. The blocks form a 130-km-wide plateau overlying the seismogenic zone and the plate boundary megathrust lies near to the base of the sediments. The sediments consist of the Nicobar and Bengal Fan turbidites and exhibit strong internal cohesion. We suggest that dewatering and lithification of the sediments during burial made them unusually competent and strong, thus enabling rupture during the 2004 earthquake to propagate beneath the plateau, close to the Sunda Trench. Extending fault rupture so close to the trench, and thus further seaward, may have enhanced the tsunami hazard by displacing a greater thickness of water.
1752-0894
453-456
Gulick, Sean P.S.
2b9eb82d-31fe-4089-9c63-cd91b1c3c6bd
Austin, James A.
babdda5a-b80d-4243-af2b-8d66ec256a0d
McNeill, Lisa C.
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
Bangs, Nathan L.B.
2b6b0ddb-8f0c-4ba6-b06e-c0e8cd3d30b5
Martin, Kylara M.
ad26d139-752e-47a8-af61-b3bf9fefdc3f
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Bull, Jonathan M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Djajadihardja, Yusuf S.
e4b6fe8a-3cd2-4c81-9fb7-62fe7b8c9346
Permana, Haryadi
b5f42881-f590-449e-b718-506ee3a1d1c8
Gulick, Sean P.S.
2b9eb82d-31fe-4089-9c63-cd91b1c3c6bd
Austin, James A.
babdda5a-b80d-4243-af2b-8d66ec256a0d
McNeill, Lisa C.
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
Bangs, Nathan L.B.
2b6b0ddb-8f0c-4ba6-b06e-c0e8cd3d30b5
Martin, Kylara M.
ad26d139-752e-47a8-af61-b3bf9fefdc3f
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Bull, Jonathan M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Djajadihardja, Yusuf S.
e4b6fe8a-3cd2-4c81-9fb7-62fe7b8c9346
Permana, Haryadi
b5f42881-f590-449e-b718-506ee3a1d1c8

Gulick, Sean P.S., Austin, James A., McNeill, Lisa C., Bangs, Nathan L.B., Martin, Kylara M., Henstock, Timothy J., Bull, Jonathan M., Djajadihardja, Yusuf S. and Permana, Haryadi (2011) Updip rupture of the 2004 Sumatra earthquake extended by thick indurated sediments. Nature Geoscience, 4, 453-456. (doi:10.1038/Ngeo1176).

Record type: Article

Abstract

During subduction, weak, unlithified sediments are scraped off the down-going plate and accumulate near the subduction trench axis. The weak nature of the sediments usually impedes the propagation of fault rupture during an earthquake. However, measurements of slip during the 2004 Sumatra–Andaman Mw 9.2 earthquake show that fault rupture propagatedupdip, extending unusually close to the subduction trench, in the southern part of the rupture area. Here we present seismic reflection images of the southern part of the 2004 Sumatra–Andaman earthquake rupture area. We show that sedimentary strata, greater than 4?km in thickness, form coherent blocks that have been thrust onto the continental margin during subduction. The blocks form a 130-km-wide plateau overlying the seismogenic zone and the plate boundary megathrust lies near to the base of the sediments. The sediments consist of the Nicobar and Bengal Fan turbidites and exhibit strong internal cohesion. We suggest that dewatering and lithification of the sediments during burial made them unusually competent and strong, thus enabling rupture during the 2004 earthquake to propagate beneath the plateau, close to the Sunda Trench. Extending fault rupture so close to the trench, and thus further seaward, may have enhanced the tsunami hazard by displacing a greater thickness of water.

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More information

Published date: 19 June 2011
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 191397
URI: http://eprints.soton.ac.uk/id/eprint/191397
ISSN: 1752-0894
PURE UUID: b390f97b-56a1-40bd-ab94-cbcc76bce966
ORCID for Timothy J. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

Catalogue record

Date deposited: 21 Jun 2011 09:31
Last modified: 29 Oct 2019 01:57

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