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Deep structure of the Longling-Ruili fault zone underneath Ruili basin near the Eastern Himalayan syntaxis: insights from magnetotelluric imaging.

Bai, Denghai and Meju, Maxwell (2003) Deep structure of the Longling-Ruili fault zone underneath Ruili basin near the Eastern Himalayan syntaxis: insights from magnetotelluric imaging. Tectonophysics, 364 (3-4). pp. 135-146. ISSN 0040-1951

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Abstract

Magnetotelluric (MT) geophysical profiling has been applied to the determination of the deep structure of the Longling–Ruili fault (LRF), part of a convergent strike-slip fault system, underneath thick Caenozoic cover in Ruili basin in southwestern Yunnan, China. The recorded MT data have been inverted using a two-dimensional (2-D) nonlinear conjugate gradients scheme with a variety of smooth starting models, and the resulting models show common subsurface conductivity structures that are deemed geological significant. The models show the presence of a conductive (5–60 Ω m) cover sequence that is thickest (1–1.5 km) in the centre of the basin and rapidly pinches out towards the margins. A half-graben structure is interpreted for the Ruili basin. This is underlain by about 7–10 km thick upper crustal layer of high resistivity (>200–4000 Ω m) that is dissected by steep faults, which we interpret to flatten at depth and root into an underlying mid-crustal conductive layer at about 10 km depth. The mid-crustal layer does not appear to have been severely affected by faulting; we interpret it as a zone of partial melt or intracrustal detachment. The MT models suggest SE directed thrusting of basement rocks in the area. The Longling–Ruili fault is interpreted as a NW-dipping feature bounding one of the identified upper crustal fragments underneath Ruili city. We suggest that MT imaging is a potent tool for deep subsurface mapping in this terrain.

Item Type: Article
Journal or Publication Title: Tectonophysics
Uncontrolled Keywords: Strike-slip fault ; Seismic hazards ; Ramp basin ; Structure ; Magnetotelluric imaging ; Partial melt
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 21364
Deposited By: ep_ss_importer
Deposited On: 12 Jan 2009 13:49
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:46
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21364

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