Japan has issued its first megaquake warning since introducing a new Earthquake Early Warnings System in 2022. The alert was triggered after a strong earthquake measuring 7.6 hit the country on Monday. Authorities have warned that more aftershocks could follow and urged people to stay cautious. On Tuesday, the government announced a top-tier warning for a possible megaquake, a massive earthquake that can create large tsunami waves and cause severe destruction.
What Is A Megaquake?
A megaquake is defined as an extremely powerful earthquake with a magnitude of 8.0 or more. If such a quake occurs, it can destroy infrastructure, damage coastal areas and lead to enormous loss of life. This is the first time Japan has issued this highest-level alert since the updated warning system came into effect in 2022. The system was designed to detect the chances of a large, damaging earthquake following a strong initial tremor.
Japan has had an earthquake early warning system since around 2007, according to the Japan Meteorological Agency (JMA). It sends alerts to residents as soon as an earthquake begins, giving information on how strong the shaking may be and when it is expected to hit.
However, the system was upgraded in December 2022 by the Headquarters for Earthquake Research Promotion and the JMA to better predict major quakes in northern Japan. In English, the system’s Japanese name roughly translates to “Hokkaido–Sanriku-offshore Aftershock Earthquake Alert Information”.
The new system works on a foreshock-based approach. It is activated only when an earthquake of magnitude 7.0 or higher has already struck specific subduction zones, such as the Japan Trench or Chishima Trench. Once triggered, it warns people that a much larger earthquake, known as the mainshock, could occur within hours or days.
After Tuesday’s warning, residents were advised to prepare for emergency evacuation. Authorities asked people to check local evacuation routes, gather emergency supplies and secure heavy items inside their homes. They were also urged to stock enough food, water and portable sanitation supplies for several days.
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Shivam Verma is a journalist with over three years of experience in digital newsrooms. He currently works at NewsX, having previously worked for Firstpost and DNA India. A postgraduate diploma holder in Integrated Journalism from the Asian College of Journalism, Chennai, Shivam focuses on international affairs, diplomacy, defence, and politics. Beyond the newsroom, he is passionate about football—both playing and watching—and enjoys travelling to explore new places and cuisines.
