Fig. 5

Dynamic triggering in the Yufuin–Beppu area. a Map for epicenters and seismic stations. The epicenter of the triggered event identified in this study marked by the star. Gray circles show other events, and triangles show the locations of the KiK-net and K-NET seismic stations. The blue line indicates the rim of the Aso caldera inferred from the topography. Red dots in the inset map denote epicenters of this earthquake sequence, and the dotted box indicates the area of the main map. b Vertical component of acceleration seismograms high-pass-filtered (HPF) at 16 Hz and sorted by distance from the hypocenter of the event γ (the bottom is closer). All traces are drawn in red after the arrival of the P-wave from the triggered event. At OIT009, the seismic waves from the event γ are invisible due to too strong waves from the triggered event. The maximum absolute value for each trace is denoted on the right. c Vertical component of acceleration records high-pass-filtered at 16 Hz from the M _w 5.1 event at 7:11 on April 16, 2016, indicated by the cross in (a). Note that different magnification factors attached to each trace are applied for different stations. d Accelerograms at the station OIT009 of K-NET, closest to the hypocenter of the triggered event. The vertical, radial, and transverse (with respect to the hypocenter of the event γ) components of the raw data, the data bandpass-filtered between 0.025 and 0.25 Hz, and the data high-pass-filtered at 16 Hz are plotted