Study locations. The red star and red triangles denote the epicenter of the 2008 Iwate-Miyagi Nairiku earthquake (M 7.2) and active volcanoes, respectively. (a) The yellow circle denotes the remote reference site (Sawauchi station). The cross-hatched area indicates the Kitakami Lowland. (b) Yellow diamonds and triangles denote MT stations in this and a previous study (Mishina 2009), respectively. Small red dots denote aftershocks of the 2008 earthquake (Okada et al. 2012).