Map views of S-wave perturbation at depths of 2.5, 10, 15, and 20 km. Black dots are earthquakes with a depth range of ±2.5 km. Red triangles are quaternary volcanoes. Red bold lines are the locations of active faults. Red squares are the stations used in this study. The rectangular box shows the approximate spatial extent of the focal area of the 2008 Iwate-Miyagi Nairiku earthquake.