Fig. 7

Displacement waveforms at station OIT009 modeled by the discrete wavenumber method. Black and red traces show the observed and synthetic waveforms of the triggered event, respectively. The synthetic waveforms are calculated from using the source time function of the pulse width of 1 s and the seismic moment M ₀ = 10¹³ Nm for a 1D velocity structure shown in Fig. 2. Both of the waveforms are high-pass filtered in a corner frequency of 0.3 Hz. The time t = 0 on the horizontal axis is the origin time of the mainshock. Shadow areas indicate the time window to calculate the variance reduction. The synthetic waveform for the mechanism obtained by the grid search for the variance reduction is shown at the bottom right