Earth Planets Space, Vol. 63 (No. 7), pp. 761-765, 2011
Hideo Aochi1 and Satoshi Ide2
1Bureau de Recherches Géologiques et Miniéres, Natural Risks and Safety of CO2 Storage Division, 3 avenue Claude Guillemin, BP36009 Orléans Cedex 2, 45000, France
2Graduate School of Science, the University of Tokyo, 1-1-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
(Received April 7, 2011; Revised May 7, 2011; Accepted May 11, 2011; Online published September 27, 2011)
We present conceptual dynamic rupture models for the 2011 Tohoku Earthquake based on multi-scale heterogeneity in fracture energy. Regardless of frequently-occurring M 7.5 events in this area, it is significant that a large-scale fault heterogeneity corresponding to a M 9 event had not been clearly recognized until this earthquake. We show that the largest heterogeneity having a high fracture energy is consistent with the relatively slow rupture propagation of the Tohoku Earthquake. The large gap in fracture energy explains the separation of two groups of waves clearly visible in observed ground motions. Our simulations favour a cascading rupture that begins from a medium heterogeneity and then progresses over larger scale heterogeneity.
Key words: 2011 Tohoku Earthquake, multi-scale, dynamic rupture, heterogeneity, ground motion.