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Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean

Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean
Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean
Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models.
0091-7613
359-362
Geersen, Jacob
abcf5f76-3608-4322-ab54-7bfb8dfcaf2d
Bull, Jonathan M.
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McNeill, Lisa C.
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Gaedicke, Christoph
2c4611ae-4943-462b-86e7-ef0c3b6af476
Chamot-Rooke, Nicolas
4ff9e1d0-d0d6-46c5-9ca9-c7b15377a209
Delescluse, Matthias
54e1642b-965b-46a4-a87e-10174c21cba9
Geersen, Jacob
abcf5f76-3608-4322-ab54-7bfb8dfcaf2d
Bull, Jonathan M.
974037fd-544b-458f-98cc-ce8eca89e3c8
McNeill, Lisa C.
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Gaedicke, Christoph
2c4611ae-4943-462b-86e7-ef0c3b6af476
Chamot-Rooke, Nicolas
4ff9e1d0-d0d6-46c5-9ca9-c7b15377a209
Delescluse, Matthias
54e1642b-965b-46a4-a87e-10174c21cba9

Geersen, Jacob, Bull, Jonathan M., McNeill, Lisa C., Henstock, Timothy J., Gaedicke, Christoph, Chamot-Rooke, Nicolas and Delescluse, Matthias (2015) Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean. Geology, 43 (4), 359-362. (doi:10.1130/G36446.1).

Record type: Article

Abstract

Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models.

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Published date: 27 February 2015
Organisations: Geology & Geophysics

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Local EPrints ID: 375750
URI: http://eprints.soton.ac.uk/id/eprint/375750
ISSN: 0091-7613
PURE UUID: de8a97ab-6922-45aa-95a4-fac9bb019e69
ORCID for Jonathan M. Bull: ORCID iD orcid.org/0000-0003-3373-5807
ORCID for Lisa C. McNeill: ORCID iD orcid.org/0000-0002-8689-5882
ORCID for Timothy J. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

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Date deposited: 02 Apr 2015 16:04
Last modified: 15 Mar 2024 03:09

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Contributors

Author: Jacob Geersen
Author: Lisa C. McNeill ORCID iD
Author: Christoph Gaedicke
Author: Nicolas Chamot-Rooke
Author: Matthias Delescluse

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