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After the earthquake that observed a maximum seismic intensity of 6 at the top of Nakadori and Hamadori in Fukushima prefecture in southern Miyagi prefecture on the night of the 13th, the Sendai District Meteorological Observatory held a press conference in the dawn of the 14. possibility of an earthquake in Japan “.
The earthquake had a magnitude (M) of 7.3 and occurred at a depth of 55 km off the coast of Fukushima prefecture. It appears to be a replica of the Great East Japan Earthquake. The earthquake with a maximum seismic intensity of 6 or more, which originated off the coast of Tohoku, has been since April 2011.
Tetsuya Shoji, an earthquake intelligence officer, explained that “after a large-scale earthquake, there will be a lot of aftershock activity even 10 years later.” The example of the 2004 Sumatra earthquake (M9.1) was given, in which the M8.6 earthquake occurred 7 years and 4 months later.
The earthquake was a “type of reverse fault” that occurred within the Pacific plate that subducted into the Earth’s plate. Regarding the Miyagiken-oki earthquake, which is expected to occur with a high probability, Mr. Shoji said: “It seems to be less relevant, but it is happening in a nearby place.”
Regarding this earthquake, Professor Ryota Hino (Underwater Seismology) from Tohoku University said: “Because the epicenter was deep, the movement of the seafloor crust was small and no tsunami occurred.”
Off the coast of Fukushima prefecture, the “side effect slippage” continues, in which the plate boundary is slowly shifting due to the effects of the earthquake. The compression force in an east-west direction is said to continue to act within the Pacific plate.
Even within the Pacific plate, a pulling force acts in an east-west direction on the east side of the Japan Trench, causing a normal fault-type earthquake. It’s called an outside rise earthquake and even if the observed shaking on the ground is small, the tsunami tends to be large. The Showa Sanriku tsunami earthquake (1933) that caused great damage to the Sanriku coast is said to be the outer rise earthquake.
Professor Hino noted: “It shows that the effects of the main shock have not diminished even after almost 10 years. We still have to watch out for the external magnification earthquake.”
