De-trended time series of selected GNSS stations in Kikaijima and Amami-oshima from 2008 to 2012. The horizontal N45°W component was plotted after removal of a linear trend for 1997 to 2013. Red and yellow vertical lines indicate the occurrence of cluster C4 SSEs and other nearby SSEs, respectively. Four-digit numbers represent GNSS station IDs. Their locations are shown in Figure 3F. An arrow indicates the occurrence of the M
6.8 interplate earthquake whose epicenter is 120 km north of Kikaijima. The coseismic displacement of the earthquake is corrected.