Spatio-temporal diagram of ΔAIC along the Ryukyu Trench. (A) Distance along the Ryukyu Trench. Broken lines are isodepth contours of the plate interface with a contour interval of 10 km. Yellow circles indicate central points of rectangular areas used to calculate average ΔAIC. (B) The stars indicate local minima of ΔAIC of -5 or lower. Blue, green, and purple stars are classified as probable short-term SSEs, possible short-term SSEs, and non-SSEs, respectively (see text). Sky blue dots represent occurrences of VLFs.