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Active faulting on the Ninetyeast Ridge and its relation to deformation of the Indo-Australian plate

DRS at CSIR-National Institute of Oceanography

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Title Active faulting on the Ninetyeast Ridge and its relation to deformation of the Indo-Australian plate
 
Creator Sager, W.W.
Bull, J.M.
Krishna, K.S.
 
Subject faults
seismic reflection profiles
tectonic boundary
plate motion
 
Description The ~4500 km long Ninetyeast Ridge (NER) in the northeastern Indian Ocean crosses a broad zone of deformation where the Indo-Australian plate is fracturing into three smaller plates (India, Capricorn, Australia) separated by diffuse boundaries whose extents are poorly defined. New multichannel seismic reflection profiles image active faults along the entire length of the NER and show spatial changes in the style of deformation along the ridge. The northern NER (0°N–5°N) displays transpressional motion along WNW-ESE faults. Observed fault patterns confirm strike-slip motion at the western extent of the April 2012 Wharton Basin earthquake swarm. In the central NER (5°S–8°S), deformation on WNW-ESE-trending thrust faults implies nearly N-S compression. An abrupt change in fault style occurs between 8° and 11°S, with modest, extension characterizing the southern NER (11°S–27°S). Although extension is dominant, narrow zones of faults with strike-slip or compressional character also occur in the southern NER, suggesting a complex combination of fault motions. At all sites, active faulting is controlled by the reactivation of original, spreading-center formed, normal faults, implying that deformation is opportunistic and focused along existing zones of weakness, even when original fault trend is oblique to the direction of relative plate motion. Observed faulting can be interpreted as India-Australia deformation in the northern NER and Capricorn-Australia deformation in the southern NER. The India-Capricorn boundary is directly adjacent to the northern NER and this juxtaposition combined with a different style of faulting to the east of the NER imply that the ridge is a tectonic boundary.
 
Date 2013-10-08T04:25:07Z
2013-10-08T04:25:07Z
2013
 
Type Journal Article
 
Identifier Journal of Geophysical Research: Solid Earth, vol.118; 2013; 4648-4668
http://drs.nio.org/drs/handle/2264/4382
 
Language en
 
Rights An edited version of this paper was published by AGU. Copyright [2013] AGU. To view the published open abstract, go to http://dx.doi.org/10.1002/jgrb.50319.
 
Publisher American Geophysical Union