Suffering earthquake (EQ) disasters, Japan has developed intensive networks of seismographs and achieved probabilistic long-/medium-term forecasting of big EQs. However, the great disaster EQs of 1995 and 2011 were never predicted. After these two EQs, Seismology Society of Japan and the government decided to avoid investigating the short-term prediction of EQs, considering it impossible. Earthquake Prediction Society of Japan has been challenging this issue since 2014 and has found a light very recently, especially by observing electromagnetic precursor phenomena.
The present paper first clarifies the requirements for the observation of precursor phenomena to be useful for a future short-term prediction alert system. Using these criteria, various research presentations are reviewed and three new presentations are found promising. Especially, M. Tsutsui observed the variation of DC electric field deep underground every second with high S/N ratio. The electric field generated by piezoelectric effect is transmitted through the earth’s crust without being disturbed by noise on the ground. In the case of EQ (on 2021/5/1, M6.8, 750 km away), the signal showed a drastic (±) variation for 46 min. 1.5 h before EQ, a sharp spike at the time of EQ, and a drastic variation for 68 min. 8.5 h after EQ. The data are excellent, showing the correlation with the EQ and containing much information about the EQ rupture process. This method is at the stage of single observation site, overcoming various practical difficulties. The present paper proposes to initiate a collaborative research project within EPSJ with several research groups and observation sites. The project will certainly step up to prove the correlation with EQs, find the method to predict EQs with 3 factors (where, when, and how large), and establish a system for short-term EQ prediction alert. The present approach is based on the TRIZ philosophy and experimental science in general and will serve Japan and all over the world.
