Fig. 6

Waveforms, spectrograms, time series windows centered on the theoretical arrival times, and STA/LTA ratio curves for events 4 and 5. (a) Earthquake with a magnitude of 6.0 Mw, which occurred on July 11, 2019, at 17:08:38. The vertical dashed lines (red/white) and the letter PKP indicate the theoretical arrival time calculated using the modified ak135f. (b) Local earthquake of magnitude 3.7 mb, which occurred on March 25, 2020, at 11:30:39. The vertical dashed lines (red/white) and the letters P, S, and T indicate the theoretical arrival times calculated using the ak135f (Fig. S41) for P-wave, S-wave and hydroacoustic phases, respectively. The ray paths of these local phases are depicted in Fig. S4. The black and grey lines are the waveforms filtered below and above 20 Hz, respectively. The red, blue and orange horizontal lines represent the preset lower and upper limits for the STA/LTA ratio trigger. The insets at the top of the figure show the global map and the ray paths of a given seismic phase. The waveforms are presented in digital units.