Fig. 1

Target area and GNSS time series. a Top: the study area in southwest Japan is marked by the black rectangle in the lower image. The red square represents the Bungo Channel SSE fault region assumed by Hirahara and Nishikiori (2019). This study assumes uniform frictional parameters both inside and outside the SSE patch indicated in the red circle. The locations of GNSS stations are marked by green triangles, with the time series for stations A–D presented in b. The temporal slip evolution, denoted by the dotted line, is shown in Fig. 2d. a Bottom: the tectonic setting of the study area, in which the Philippine Sea Plate (PH) subducts beneath the Amurian Plate (AM) along the Nankai Trough. b Examples of GNSS time series at stations identified in a. The displacements in trench-parallel (X), trench-perpendicular (Y), and vertical (Z) components are represented by green, blue, and black dots, respectively. The red lines depict the calculated time series, derived from 100 frictional parameters sampled from the posterior PDF of the model parameters. Note that the red lines largely overlap, making it visually difficult to distinguish the 100 time series in each component. GNSS = Global Navigation Satellite System