Fig. 1

Tectonic settings around the Shikoku region. Solid lines are the plate boundaries, as per the study by Bird (2003). AM, NA, PA, and PH denote the Amurian, North American, Pacific, and Philippine Sea plates, respectively. TB and BC denote the Tosa Bay and the Bungo Channel areas, respectively. Small crosses denote the GEONET stations that were used in this study, whereas the black square denotes GEONET 940075, which was used as a fixed point. Blue and red contours show the coupling and the long-term SSE in BC between 2010 and 2011, and dark red rectangles show fault models of the short-term SSE published by Sekine et al. (2010)