Tsunami Warning Japan: Its System, App, and Latest Warnings

Japan is located in an active seismic zone. Therefore, this country is highly prone to earthquakes and tsunamis. Centuries ago, Japan suffered severely from tsunamis. Nowadays, an effective tsunami warning Japan system has helped the government to manage this disaster.

Japan’s residents usually receive an early tsunami alert a few minutes after the earthquake. The warning may come in several forms, including cell broadcasts, announcements, and TV broadcasts. Moreover, the warning allows people to have enough time to seek shelter before the tsunami sweeps the shore.

Japan’s Early Tsunami Warning System

The early tsunami warning system in Japan is managed by JMA (Japan Meteorological Agency). This system is one of the most advanced systems. Japan first developed the system in the 1940s. Since then, the system has undergone several improvements and changes. 

Its latest improvement was in 2013. At that time, the government improved the system in response to the 2011 Great East Japan Earthquake. Below are the characteristics of this system.

1. Rapid Tsunami Detection

The system of tsunami warning Japan contains modern tools and sensors, including seismometers, offshore pressure sensors, and sea-level gauges. Each of those sensors collects different data, e.g., seismic data, water pressure changes, and sea-level changes.

The system will collect data from those sensors to detect a tsunami. Japan’s tsunami early warning system will then use the data to forecast and model a tsunami. 

If the system detects a tsunami, it will issue a tsunami warning after Japan earthquake alerts. The dissemination of this warning  is typically within 3 minutes after the tremor.

2. Tsunami Warning Categories

Before the improvement in 2013, Japan’s tsunami warning system did not inform the category or scale of the tsunami. Consequently, some people underestimated the warning. 

It is understandable because some earthquakes generate only 20-cm tsunamis, while others can generate 10-m waves. This phenomenon is one of the causes of the high fatalities in the 2011 tsunami. 

Therefore, Japan’s authorities have described the category of the tsunami in the warning message since 2013. These categories are as follows. 

• Tsunami Advisory: JMA will issue a tsunami advisory if the tsunami wave is up to 1 m.

• Currently Observing: Authorities will disseminate an alert with a message of ‘currently observing’ if the tsunami wave is smaller than forecasted. Those who get this message must stay in higher places because bigger waves may come.

• High Tsunami Warning: JMA will use the word ‘high’ in the tsunami warning if the wave is estimated to be up to 3 m.

• Huge Tsunami Warning: This category indicates that the incoming tsunami is higher than 3 m.

3. Multi-Channel Dissemination

JMA uses multi-channel dissemination to ensure all people in the affected areas get the warning. Therefore, authorities can save as many people as possible. Below are channels used for disseminating Japan’s tsunami warnings.

• Outdoor and Indoor Speaker: Authorities installed a Simultaneous Wireless Announcement System in strategic places, including schools, hospitals, and street towers. JMA will announce a tsunami warning through this speaker system after an earthquake.

• Mass Media: JMA will also intervene in radio and TV programs to announce a tsunami warning. This announcement is programmed in bilingual audio and accompanied by map overlays.

• Mobile Alerts: People in the affected areas will also get cell broadcast push notifications on their mobile phones. This communication channel allows fast alert dissemination because it is resilient to network congestion.

Tsunami Warning Japan Apps

Aside from the communication channels above, Japan also has several apps for communicating tsunami alerts and information on earthquakes and tsunamis. Some of them are great for tourists visiting Japan because the alerts and information in those apps are available in English and other languages.

• NERV Disaster Prevention: This Japan tsunami warning app offers fast and detailed warnings for tsunamis and other disasters. This app also provides English language support. Moreover, users can customize their region in the app. Thus, they will get relevant tsunami warnings.

• NHK World Japan: This app is excellent for tourists because it provides a Japan Meteorological Agency tsunami warning in English. These warnings also contain detailed information, including estimated tsunami height and the affected areas.

• Safety Tips: This app is provided by the Japan Tourism Agency for foreign tourists. This app offers safety tips and disaster information, including tsunami warnings in the user's chosen language. Therefore, foreign tourists in Japan can get tsunami notifications on their cell phones.

Recent Tsunami Warnings in Japan

Currently, there are no active tsunami warnings in Japan. However, in the first half of December 2025, JMA issued two tsunami warnings. The first was on December 8. 

Japan’s authorities issued the warning after a magnitude 7.5 earthquake occurred off the Aomori coast. Thankfully, the tsunami was less than a metre high. Moreover, authorities cleared the tsunami advisories on December 9.

The second one was on December 12. This tsunami warning was issued after the aftershock of the Aomori earthquake. The magnitude 6.9 earthquake generated a small tsunami of only 20 cm high.

The system of tsunami warning Japan is the best worldwide. It issues tsunami alerts within 3 minutes after the earthquake. One of the factors making this system fast and effective is the cell broadcast technology. Other countries can also adopt similar technology from smsbroadcaster.com.