Lyell Collection
Geological Society, London, Special Publications
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fabbri, O.
Right arrow Articles by Kanaori, Y.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Geological Society, London, Special Publications; 2004; v. 227; p. 141-165;
DOI: 10.1144/GSL.SP.2004.227.01.08
© 2004 Geological Society of London

Vertical Axis Block Rotations in the Upper Crust, Horizontal and Vertical Partitioning and Implications for Vertical Coupling-Decoupling in the Lighosphere

Distributed strike-slip faulting, block rotation and possible intracrustal vertical decoupling in the convergent zone of SW Japan

Olivier Fabbri1, Kazumasa Iwamura2, Satoshi Matsunaga3, Guilhem Coromina1 & Yuji Kanaori4

1 EA 2642, Université de Franche-Comté, 16 route de Gray, 25030 Besançon Cédex, France olivier.fabbri{at}univ-fcomte.fr
2 Iwakuni High School, Iwakuni 741-0082, Japan
3 Nissaku Co., Joetsu 950-2181, Japan
4 Department of Geology, Faculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan

Between the Median Tectonic Line (MTL) and the Japan Sea, the western Chugoku region of SW Japan is cut by a series of N45°E first-order faults and oblique (N60°–N170°E) second-order faults. This fault network, probably formed during Late Cretaceous-Palaeocene times (70–60 Ma), defines a regional block structure. Pre-Plio-Quaternary kinematical indicators suggest left-lateral motion along the first-order faults and right-lateral motion along some of the second-order faults. Geomorphological evidence and earthquake focal mechanisms indicate that Plio-Quaternary slip senses are opposite to Pre-Plio-Quaternary ones.

The overall fault pattern is geometrically and kinematically similar to patterns obtained by experimental modelling of simple shear deformation distributed at the base of a brittle layer analogue over its entire width. This similarity suggests the possibility of a mid-crustal, flat-lying partial attachment zone which could have controlled the formation of the western Chugoku fault network in Cretaceous to Palaeocene times. The zone, presently inactive, could correspond to the ‘proto-MTL’, a low-angle fault recently imaged by seismic reflection studies and whose trace approximately coincides with the present-day MTL.

Reactivation of the system occurred twice after its formation: firstly in Miocene times, during the opening of the Japan Sea and concomitant clockwise rotation of the entire SW Japan arc; and secondly in Late Pliocene to Quaternary times, after a shift of the relative direction of convergence between the Philippine and Eurasia plates. Unlike the first reactivation, the second reactivation led to an inversion of the sense of slip along the faults.