What Happened?

Japan has issued an advisory warning of a potential “megaquake” – a very large earthquake – following a seismic event that struck off the country’s eastern coast on Monday, December 9, 2025. The Japan Meteorological Agency (JMA) announced the “Off the Coast of Hokkaido and Sanriku Subsequent Earthquake Advisory” on Tuesday, December 10, 2025, citing an increased assessment of earthquake activity in the region.

While officials emphasize that a significant earthquake is not certain, the advisory urges residents to prepare for potential seismic activity. The initial earthquake on monday prompted a tsunami advisory, which has since been lifted, but the underlying increased seismic activity remains a concern.

Preparedness Measures Advised

The JMA is advising residents, nonetheless of whether their area was directly affected by Monday’s earthquake, to prioritize disaster preparedness over the next week. Key recommendations include:

• Closely monitoring information from the Japan Meteorological Agency (JMA).
• Staying informed through updates from local authorities.
• Confirming earthquake preparedness, including identifying safe evacuation sites and routes.
• Securing furniture and other objects that could pose a hazard during shaking.
• Being prepared to evacuate promptly if any shaking is felt.

Understanding the Advisory

Officials have clarified that the advisory is not a forecast of an impending earthquake. The probability of a magnitude eight or greater earthquake occurring remains at approximately one percent. However, the advisory serves as a crucial reminder for citizens, particularly in light of the catastrophic 2011 Tōhoku earthquake and tsunami, which resulted in nearly 20,000 fatalities and the Fukushima Daiichi nuclear disaster. World Vision provides a detailed overview of the 2011 disaster and its impact.

The 2011 earthquake, officially designated as the Great East Japan Earthquake (東日本大震災, Higashi Nihon Daishinsai), measured 9.0-9.1 on the moment magnitude scale, making it one of the most powerful earthquakes ever recorded. The subsequent tsunami caused widespread devastation along the northeastern coast of honshu, Japan.