HR: 1330h
AN: T52B-0267    [PDF]
TI: Southern extension of the Sumatra Fault and its tectonic significance
AU: * Soh, W
EM: soh@jamstec.go.jp
AF: Japan Marine Science and technology center, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Gaedicke, C
EM: Gaedicke@bgr.de
AF: Federal Institute for Geoscience and Natural Resources, Stilleweg 2, D-30665, Hannover, D-30665 Germany
AU: Djajadihardja, Y S
EM: iyung24@yahoo.com
AF: Agency for the Assessment and Application of Technology, BPPT II Bld. 19th floor, J.H. Thamrin No.8, Jakarta, 10340 Indonesia
AU: Saito, S
EM: saito@jamstec.go.jp
AF: Japan Marine Science and technology center, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AB: Mode of slip partitioning in a fore arc of Sunda Arc between near trench normal thrusting and trench-parallel strike-slip faulting has been postulated mainly from the study of earthquake slip vectors and slip rate of the strike slip Sumatra Fault. However, there is no dependable geomorphic data, despite great attention for the area off the Sunda Strait which represent the junction between normal subduction off Java and oblique subduction off Sumatra. New single channel and bathymetric data were obtained by R/V Yokosuka, YK01-02/YK02-07 cruises and they provide a quite different geomorphologic view to the previously knowledge. New discovery of the southern extension of the Sumatra Fault is an example. In the southern extension, Shinkai 6500 dives allow us to identify more or less a meter of vertical topographic displacement along the SSE-trending active fault. Several amount of mud diapir mounds and a few sink hole are first recognized in the area where corresponds to a significant negative Bouguer anomaly zone. A methan content anomaly is detected in the summit of the mounds and bottom floor of the sink hole, together with Calyptogena colony. On the other hand, geomorphologic feature in the junction area is quite different to those of forearc setting; the area is covered by a bundle of tectonic blocks including the Genteng Bank, that well demarcated by the SSE- and east-trending conjugate lineaments. The junction area extending toward SSE occupies between the fore arc basin and the outer arc high and is demarcated by faults. The boundary fault cuts the preexisting geomorphology including trench-parallel strike slip fault in the outer arc high; e.g. Mentaiwai Faults. Consequently these geomorphic feature, as an accumulation of crustal deformation (plastic strain), is most likely to be caused by stretching of the fore arc crust. This study suggests that strain (plastic) partitioning in a fore arc occurs within the localized (or concentrated) area such as the junction, although elastic strain is uniformly spread over the entire fore arc.
DE: 1206 Crustal movements--interplate (8155)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting