Japan’s New Undersea Earthquake Detection System Will Improve Tsunami Prediction

Japan films the ocean with a “nervous system” detecting earthquakes

By Deni Ellis Béchard Edited by Dean Visser

If the bottom of the ocean had a nervous system, it could look like this: thousands of kilometers of fiber optic cables connected to sensors at the top of the fault lines where the earthquakes of Japan begin. Finished in June, this system aims to avoid devastation like that of 2011 – when a relentless six -minute temblor was followed by a 130 -foot tsunami which reached speeds of 435 miles per hour and cities pounded in rubble. Delayed alerts have given certain communities for less than 10 minutes to evacuate and only warned of much smaller waves, based on inaccurate earthquakes. Nearly 20,000 people died, with thousands of more injured or missing people. The reactor collapses at the Fukushima Daiichi flooded nuclear power plant radiated the surrounding land and overthrow radioactive water in the ocean.

The underwater “Magathrust” earthquake, of magnitude 9.0 – The worst in recorded history of Japan – Began in the seabed of the Pacific to 45 miles off the eastern coast of the country. Land sensors detected its first shock waves but could not immediately provide clear readings of its magnitude or that of the tsunami which it created. A few months later, Japan began to extend its earthquake detection system to cover the bottom of the ocean. With the completion of the system last month, Japan became the first country to obtain direct and real -time surveillance from whole subduction zones, adding minutes and seconds to evacuate people and prepare a crucial infrastructure for the impact.

But the advanced warning system is not the whole story, explains the seismologist Harold Tobin, director of the seismic network of the North West Pacific. “By wiring the offshore fault area, we are constantly able to listen to it,” he said. “This means that we can detect all kinds of subtle signals that tell us how defects work, such as stress storage and how it starts to be released at the start of an earthquake.”

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Japan builds its “nervous system” of the oceanic soil

A few months after the 2011 earthquake, the Japanese government began to build S-Net (Seafloor Observation Network for earthquakes and tsunamis). S-Net has won the country’s earthquake detection network in the Japanese trench, the sectionally active offshore region where the 2011 earthquake started. About 3,540 miles of cable now zigzag in 116,000 square miles of ocean to connect 150 observatories to the bottom of the ocean. Each contains 14 separate detection channels, including seismometers and accelerometers, as well as the manometers to measure the waves passing over the head. This network – The first part of the largest network completed in June 2025 – was completed in 2017. When a magnitude 6.0 earthquake hit the following year, the alerts reached cities before the first stroke of the sect – a complete 20 seconds before the earthly seismometer closest to its alarm, which is precious time to slow down ballet trains and dissemination ruptures.

A much smaller seabed network, the Donet (dense network system on earthquakes and tsunamis) had been launched in 2006 along a section of Nankai Trough, another geologically active area, where the Philippine Marine plaque pushes under the southwest of Japan. This area had been considered a most urgent seismic threat in Japan. The last pair of ruptures over 8.0 years had taken place there in 1944 and 1946. And because the historic intervals for major earthquakes in this area occur on average from 100 to 200 years, the stress between the plates was supposed to approach its breakdown. The Nankai megathrust area is only 40 to 60 miles off the poles densely populated by Osaka and Nagoya and the Kai industrial belt; And the geometry of the region’s trenches targets tsunamis directly on the shore. Catastrophe plans project hundreds of thousands of victims and economic losses of more than 1 dollars if the warnings only arrive after land sensors. In 2013, Donet was extended to include more than 460 miles of cables. And in 2019, the N-Net recently completed (Nankai Trough Seafloor Network for earthquakes and tsunamis) began; It currently covers the rest of the Nankai Megathrust area. Connected by more than 1,000 miles of cable, the 36 N-net observatories complete the largest japan earthquake detection system.

With the final N-Net link set up in June, the complete system increases the warning times of 20 seconds for earthquakes and the 20 full minutes for tsunamis, which is still time to divert incoming flights and close sea doors in animated ports. And the project could provide seismologists with a treasure of new useful data. Slow -slip events are particularly interesting, in which defects are gradually released without earthquakes. “If you wrap the 20 -year -old stopwatch, we essentially thought that the faults were locked and did not move at all or had an earthquake and moved very quickly,” said Tobin. But slow slip events reveal a third mode in which defects move faster than the tectonic rate of regular plaque but much slower than an earthquake. While slow -sliding events are generally not present before small earthquakes, they often occur in the days preceding the main ones – perhaps detaching “enough the fault zone to prepare the system for a large earthquake”, says Tobin. “It could end up being something that we can use as an earthquake detection system.” It is quick to emphasize, however, that all slow slip events are not followed by earthquakes.

N-N-Net technicians will spend the months calibrating instruments to calibrate and bend their food into a single back surveillance spine which includes around 6,000 Terresters in Japan. But the most difficult part is finished: installing cables and observatories armored in fiber optics and observatories along the abyssal plain of ships and “plowing” the shallow seafood areas to bury cables and protect them from anchors and fishing equipment. The underwater robots have helped in deeper waters and will now serve observatories and will replace the parts.

Nuclear bombs detectors with tsunami alarms

The completion of the Japanese network coincides with that of another tsunami detection program at Cardiff University in Wales. A large (early global assessment in real time of tsunamis) occurred online in June and disseminates data from four of the 11 stations of the Hydroacoustic Ocean created for the complete organization of the nuclear test Treaty. Built to listen to explosions of clandestine nuclear bombs, the globe Spanning system detects waves of acoustic gravity at low frequency. These pressure impulses sprint through seawater at around 3,355 miles per hour, more than 10 times faster than the tsunami attack edge. Researchers at the University of Cardiff use automatic learning algorithms to interpret hydrophone signals. In a few seconds, the system estimates the extent of the earthquake, the type of flawing shift and the potential of tsunami and sends alerts, although researchers believe that a total of two dozen hydrophone sites would be necessary to make global coverage.

Cascadia silent Megathrust: a massive earthquake pending invisible

Even as these detection systems develop, however, one of the most vulnerable flaws on the planet remains among the least monitored: the fault of the megathrust of Cascadia, which runs along the Pacific coast to the northwest of the island of Vancouver to the north of California. Unlike Japan faults, it does not produce many small earthquakes, which initially led seismologists to believe that it posed little risk. But recent research has shown that it is subject to rare but massive earthquakes. In contrast striking with Japan, the Mégathrust Cascadia flaw has only one cable with three seismometers, although the funding has recently been obtained to replace one of the seismometers and add three others. (Canada also has a small cable system in place.) “We just have the most exciting beginnings of what they have in Japan,” said Tobin. Early detection of a massive earthquake could give more time to prepare tens of millions of people along the northwest coast of the Pacific, as is the detection of slow slip events in the fault. “We understand really very well now that it only puts stress towards a very large -on the scale of magnitude and on a potential scale -, just as big as 2011, with the same risk of tsunami,” he said. “It’s quite inevitable.”