Japan has experienced a surge in seismic activity over the past week, with 52 earthquakes recorded between 8:00 on April 13 and 8:00 on April 20, 2026. Among these, six events reached a maximum intensity of 3 or higher, all of which were centered in the northern region of Nagano Prefecture.
Significant Activity in Northern Nagano
The region saw a particularly volatile period on April 18. At approximately 13:20, a magnitude 5.0 earthquake struck, resulting in an intensity of 5-upper in Omachi City and 5-lower in Nagano City.
Roughly one and a half hours later, at 14:54, a second significant event occurred. This magnitude 5.1 earthquake produced intensity 5-lower tremors in both Nagano City and Omachi City.
Risk Assessment and Future Outlook
The Japan Meteorological Agency has noted that historical data shows instances where similar earthquakes have continued to occur within a week of a major event. Residents in heavily affected areas are urged to remain vigilant.
There is a possibility that earthquakes of intensity 5-upper could occur within a week of the initial shocks. The agency warns that even stronger tremors may potentially occur, necessitating continued caution.
Immediate Response Guidelines
When an Earthquake Early Warning is issued or shaking begins, immediate and calm action is essential. Inside the home, individuals should protect their heads and seek shelter under sturdy furniture, such as desks.
It is advised not to rush outdoors or attempt to extinguish fires during the shaking. Opening doors to secure an evacuation route is also a key safety measure. Those in elevators should stop at the nearest floor and exit immediately.
For those outdoors, the primary risks include collapsing block walls, falling signs, and shattered glass. If a sturdy building is nearby, it is safer to seek shelter inside. Drivers should avoid abrupt braking, slow down gradually, apply hazard lights, and pull over to the left side of the road.
In mountainous areas or near cliffs, residents must stay alert for potential rockfalls or landslides.
Long-term Preparedness Strategies
Because earthquakes occur without warning, systemic preparation is the only reliable defense. This includes maintaining a stock of emergency water and food, as well as a ready-to-go emergency kit.
Experts recommend “rolling stock,” a method of consuming stocked supplies and replacing them as they are used. Securing furniture to prevent it from blocking exits and applying shatter-proof film to glass can significantly reduce indoor risks.
Families are encouraged to pre-determine meeting points and communication methods. It is also vital to identify dangerous spots on daily commute routes, particularly in areas with weak ground where rain could trigger landslides following seismic activity.
For more detailed data, you may refer to the seismicity map or the activity level reports.
Frequently Asked Questions
How many earthquakes occurred between April 13 and April 20, 2026?
There were 52 earthquakes in total, with six of those reaching a maximum intensity of 3 or higher.
Which areas in Nagano were most affected on April 18?
Omachi City and Nagano City experienced the strongest shaking, recording intensities of 5-upper and 5-lower during two separate magnitude 5.0 and 5.1 earthquakes.
What is the “rolling stock” method for emergency supplies?
Rolling stock is a preparation strategy where you maintain a stockpile of food and water, using the items as part of your daily life and replacing them as they are consumed to ensure supplies remain fresh.
Have you checked the stability of your furniture and the safety of your daily commute routes recently?
