"Japan Earthquake, Large Aftershocks Possible Over the Next 10 Years"

Aftermath of the Great East Japan Earthquake
Over 15,000 Aftershocks in the Past 10 Years... Five Events of Magnitude 7.0 or Higher

[Image source=AP Yonhap News]

[Asia Economy Reporter Kwon Jae-hee] On the 13th, a magnitude 7.3 earthquake occurred off the coast of Fukushima Prefecture, Japan, and there is growing attention as forecasts suggest that strong aftershocks will continue for a long period.

According to the Mainichi Shimbun on the 16th, the Japanese government's Earthquake Research Committee announced that this earthquake is an aftershock of the Great East Japan Earthquake (magnitude 9.0) that occurred in March 2011, and that a situation where large-scale aftershocks occur will continue for the time being.

Naoshi Hirata, chairman of the Earthquake Research Committee and professor emeritus at the University of Tokyo, said, "Although the number of aftershocks has decreased since the Great East Japan Earthquake occurred 10 years ago, at least under the current circumstances, I think such aftershocks will continue for about another 10 years."

The Japan Meteorological Agency defines a rectangular area stretching obliquely north to south about 350 km wide and about 600 km long, from the sea off Aomori Prefecture at the northernmost tip of Honshu to Chiba Prefecture in the metropolitan area, as the aftershock zone of the Great East Japan Earthquake.

Earthquakes occurring in the aftershock zone after the Great East Japan Earthquake are automatically considered aftershocks, and since the occurrence of the Great East Japan Earthquake until the 14th of this month, a total of approximately 14,647 aftershocks have occurred.

During the same period, a total of five aftershocks with a magnitude of 7.0 or higher occurred.

[Image source=Reuters Yonhap News]

Regarding the occurrence of aftershocks even 10 years after the earthquake, the academic community views this as a normal occurrence.

According to a report by the Tokyo Shimbun citing Professor Naoyuki Kato of the Earthquake Research Institute at the University of Tokyo, "When a large earthquake occurs, faults move and the forces applied to the bedrock are redistributed," and "earthquakes that occur to avoid disturbing those forces are aftershocks, and it is not unusual for them to continue for over 100 years."

He cited the ongoing aftershocks of the magnitude 8.0 Nobi earthquake that occurred in southern Gifu Prefecture in October 1891 as an example.

There are also criticisms that the method of classifying all earthquakes in the aftershock zone as aftershocks is problematic. Strictly speaking, earthquakes caused by separate reasons from the Great East Japan Earthquake can also be classified as aftershocks. There are also concerns that the term "aftershock" may lead to underestimating the risk of earthquakes.

Professor Takashi Furumura of the Earthquake Research Institute at the University of Tokyo pointed out, "The sea off Fukushima Prefecture is an area where large earthquakes frequently occur every 40 years, and even without the earthquake caused by the Great East Japan Earthquake, this earthquake could have occurred," adding, "We should not be optimistic just because it is called an aftershock."

Meanwhile, the Sankei Shimbun reported that the Japan Meteorological Agency is reconsidering whether to revise its operational method of announcing all earthquakes occurring in the aftershock zone as aftershocks of the Great East Japan Earthquake.

This content was produced with the assistance of AI translation services.