Fig. 1

Seismic stations and hypocenters used in this study and example of waveform on transverse component at DP.YGI. a Gray dots represent hypocenters. Red and green triangles represent temporary and permanent seismic stations, respectively, of Kyoto University, AIST, NIED, and JMA. Blue stars represent hypocenters of deep low-frequency earthquakes (DLFs). Black lines indicate the location of active faults. Green lines show the depth contours of the upper boundary of the Philippine Sea plate reported by Hirose et al. (2008). b In the inset map, the black star and circle represent the hypocenter of a M2.0 earthquake on March 8, 2010, and seismic station (DP.YGI), respectively. This waveform is unfiltered by a 5–8-Hz band-pass filter