Earth Planets Space, Vol. 59 (No. 6), pp. 499-512, 2007
Bunichiro Shibazaki1, Kazuteru Garatani2, and Hiroshi Okuda3
1International Institute for Seismology and Earthquake engineering, Building Research Institute, 1 Tatehara, Tsukuba, Ibaraki 305-0082, Japan
2ITOCHU Techno-Solutions Corporation, 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo 100-6080, Japan
3Research into Artifacts, Center for Engineering, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568, Japan
(Received February 13, 2006; Revised December 4, 2006; Accepted January 15, 2007; Online published June 27, 2007)
A finite element analysis with non-linear visco-elasticity and plasticity was carried out with the aim of constructing a model of the slip and deformation processes in the deeper parts of the seismogenic zones of inland earthquakes. Our finite element code is based on the GeoFEM parallel finite element code and was developed using plug-ins to adopt several non-linear functions. We consider the effects of geothermal structures in the crust in a compressional tectonic setting to model the deformation and faulting that occur around the Ou Backbone Range in northeastern Japan. We set an area of high geothermal gradient in the center of the model. The numerical results show that shortening deformation due to non-linear viscous flow occurs in the high-temperature area in the lower part of the crust, which results in shear faulting in the upper part of the crust. In the case where the crust comprises two layersthe upper crust (quartz diorite) and the lower crust (wet diabase)a weak viscous zone appears in the lower part of the upper crust and a strong viscous or plastic zone appears at the upper part of the lower crust. Our numerical results are able to explain the deformation and faulting that occur around the Ou Backbone Range in northeastern Japan.
Key words: GeoFEM, crustal deformation, non-linear visco-elasticity, plasticity, thermal structure, Ou Backbone Range.