The Hokkaido Eastern Iburi Earthquake occurred on September 6, 2018. The seismic intensity of 7 was recorded in Atsuma Town, and the seismic intensity of 6+ was recorded in Abira Town, and Mukawa Town, Hokkaido. 17 minutes after the earthquake, the entire Hokkaido region was blacked out due to the collapse of the entire power transmission and distribution system.
Immediately after the earthquake, the power supply frequency temporarily dropped to 46.13 Hz due to the shutdown of turbines at the Tomatoh Atsuma Thermal Power Station (Units 2 and 4). With the emergency operation of the Hokkaido-Honshu HVDC Link started, the recovery trend turned toward 50Hz, but after that, the eastern Hokkaido area became an isolated system, and the hydroelectric power plant stopped due to the increase in frequency, and the Hokkaido-Honshu HVDC Link was in full operation. As a result, I could not afford it. Subsequently, the Tomatoh Atsuma Thermal Power Station (Unit 1) was shut down due to a damaged boiler tube. The supply-demand balance for the entire Hokkaido region began to collapse, causing power resilience to deteriorate, resulting in the blackout.
Thus, the unprecedented all-province blackout was caused by a combination of multiple factors, including the shutdown of wind and hydroelectric power plants due to a drop in frequency and rapid recovery, and a broken boiler tube at the Tomatoh Atsuma Thermal Power Station (Unit 1).