News Summary:
- The Aomori earthquake on December 8, 2025, can be communicated to the public 3 seconds faster thanks to S-Net, Japan’s most advanced underwater sensor network.
- This system detects earthquakes directly from the seabed via fiber optic cables, then sends real-time data to the Japan Meteorological Agency for early warning.
- Built after the 2011 tragedy, S-Net is now a key pillar of Japan’s disaster mitigation.
Correspondent’s Report, Richard Susilo from Japan
, TOKYOThe Aomori earthquake on December 8, 2025, at 11:15 PM, was detected and communicated to the public 3 seconds earlier.
It turns out that was thanks to Japan’s S-Net underwater network system, which can detect earthquakes earlier.
“Japan continues to strengthen its disaster mitigation system by relying on S-Net (Seafloor Observation Network for Earthquakes and Tsunamis), an advanced underwater sensor network designed to detect earthquakes and tsunamis more quickly and accurately,” a source at the Japanese digital ministry revealed last week.
Thanks to this system, the earthquake in Aomori on December 8, 2025, can be detected and disseminated to the public 3 seconds faster than before.
“S-Net is the world’s largest earthquake and tsunami monitoring network, installed on the seabed along the Pacific coast of Japan, especially in the Tohoku to Kanto region, an area prone to megathrust earthquakes,” he added.
This system was developed after the major earthquake and tsunami tragedy on March 11, 2011, which killed over 18,000 people and triggered the Fukushima nuclear crisis. The system has been fully operational since 2018.
Faster Detection from the Seabed
Unlike conventional systems that rely on land-based sensors, S-Net uses seismometers and seawater pressure sensors connected via fiber optic cables on the seabed. With this technology, plate movements and changes in sea pressure can be detected several minutes earlier, a crucial time for the evacuation of coastal residents.
Data from S-Net is sent in real time to a monitoring center and utilized by the Japan Meteorological Agency (JMA) to issue early earthquake and tsunami warnings.
Built to Avoid Warning Delays
The Japanese government assessed that during the 2011 disaster, limitations of land-based sensors caused tsunami warnings to be not fast enough to save many victims. S-Net was designed to close that gap by detecting earthquake sources directly from the sea, the initial location where large earthquakes occur.
This network is managed by the National Research Institute for Earth Science and Disaster Resilience (NIED) in collaboration with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
Japan Disaster Mitigation Pillar
S-Net has now become one of the main pillars of Japan’s disaster mitigation strategy, alongside its earthquake early warning system and tsunami simulations. Experts consider this system to be crucial in facing the potential for major earthquakes in the Japan Trench and Nankai Trough in the future.
The Japanese government hopes that by utilizing S-Net, the number of casualties from earthquakes and tsunamis can be minimized, while also increasing public preparedness in facing natural disasters.
As a country located in the Pacific Ring of Fire, Japan asserts that investing in disaster mitigation technologies like S-Net is a vital step in protecting lives and national infrastructure.
The S-Net network is located off the northeast coast of Honshu Island to the east of Hokkaido. The system consists of approximately 5,800 kilometers of submarine cable connecting 150 observation points resembling repeaters, with a distance of about 30 kilometers between points, as well as six cable landing points on land.
Each S-Net observation point is equipped with four accelerometers for short-term and long-term seismic activity measurements, as well as two pressure sensors (as a backup system) that function for tsunami detection and monitoring of seafloor surface changes.
The existence of this network makes a significant contribution to the development of disaster science, especially in earthquake monitoring and tsunami early warning in earthquake-prone areas of Japan.
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