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

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

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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.

Document Type: Article
Additional Information: WOS:000352097900027
Keywords: Wharton Basin; Indian OceaN ; Oceanic plate ; Riedel shears ; Fracture zones ; Intraplate earthquakes ; Strike-slip deformation ; 2012 Sumatra earthquakes
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
DOI etc.: 10.1130/G36446.1
ISSN: 0091-7613
Projects: SeaCause
Expeditions/Models:
Date Deposited: 25 Mar 2015 15:07
Last Modified: 17 May 2017 07:51
URI: http://eprints.uni-kiel.de/id/eprint/28360

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