Oceanic mantle reflections in deep seismic profiles offshore Sumatra are faults or fakes

Type Article
Date 2019-09
Language English
Author(s) Sibuet Jean-Claude1, 2, 3, He Enyuan1, 4, Zhao Minghui1, 4, 5, Pang Xinming1, 5, Klingelhoefer FraukeORCID3
Affiliation(s) 1 : Chinese Acad Sci, South China Sea Inst Oceanol, Key Lab Ocean & Marginal Sea Geol, Guangzhou 510301, Guangdong, Peoples R China.
2 : 244 Rue Cloitre, F-29280 Plouzane, France.
3 : Ifremer Ctr Brest, BP 70, F-29280 Plouzane, France.
4 : Chinese Acad Sci, Innovat Acad South China Sea Ecol & Environm Engn, Guangzhou 510301, Guangdong, Peoples R China.
5 : Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China.
Source Scientific Reports (2045-2322) (Nature Publishing Group), 2019-09 , Vol. 9 , P. -
DOI 10.1038/s41598-019-49607-x
Abstract

In the late 90's, some faults identified within oceanic crust were demonstrated to be artifacts arising from out-of-plane scattering along linear sediment-buried fault scarps. Symmetrical mantle reflections observed southwest northern Sumatra on seismic reflection profiles have been identified as faults cutting through the upper mantle down to unprecedented depths reaching similar to 45 km. Seawater being conveyed along sub-vertical re-activated fracture zones (FZs) to the upper mantle, the mantle portions of FZs are serpentinized and act as mirrors for seismic rays. We suggest that the mantle features are not faults but artifacts resulting from out-of-plane reflections on these mirrors. Two perpendicular seismic profiles crossing the same FZ display two dipping features down to 30 km, which cannot be explained as faults from recent tectonic and structural constraints but merely as out-of-plane reflections on this FZ. This result confirms that most of mantle reflections observed southwest northern Sumatra are fakes rather than faults.

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