Red star is the instrumental epicenter of the main shock from Chen and Molnar (1977).
This third mode is a free gravity wave appearing in the TEC ~45 min after the main shock, from a distance of ~400 km away from the epicenter.
The ΔCFS was positive at and near the hypocenter of the main shock; therefore, the aseismic slip would have encouraged the rupture initiation of the main shock and may be able to explain the delay for 28 h of the main shock from foreshock 1, as pointed out by Kato et al. (2016a).
We then consider whether the amplitudes or τc could discriminate the main-shock from the smaller foreshocks during the initial portion of their waveforms.
Yoshida et al. (2011) derived a slip distribution during the 2011 main-shock from teleseismic P-waves and regional strong motion data, and the results of Yoshida et al. (2011) are considered to be suitable for comparison with the aftershock distribution, because the slip distribution using strong motion data should correspond with the radiation of seismic waves.
Aftershocks are indistinguishable from main shocks, but they do have some predictable qualities, including their frequency.
Wyss and Habermann (1988) summarized seventeen cases of precursory seismic quiescence to main shocks with magnitudes ranging from M = 4.7 to 8.0, and found that (1) the rate of decrease ranges from 45%to90%0%, and (2) the duration of the precursors ranges from 15 to 75 months.
During the 2016 Kumamoto earthquake sequence, in addition to the damage caused by the main shock, damage from the foreshock was significant.
Total geodetic moment (GM) release in our fault model is 3.47 × 1019 Nm (M w 6.96), whereas seismic moment (SM) of the main shock derived from JMA catalog is 4.06 × 1019 Nm (M w 7.01) (Table 3).
Ground motion from these main shocks and a number of aftershocks were recorded at the Icelandic strong motion network operated by the University of Iceland.
