Cosmic ray detector detects tsunami for the first time

The detector system in a tunnel under Tokyo Bay can detect fluctuations of muons in the sea, helping to identify tsunamis.

Tsunamis can have dire consequences. This prompted the scientific community to improve the methods to detect this disaster. Research published in the journal Scientific Reports on April 12 points to a promising solution to help detect tsunamis: monitoring muons.

Muons are high-energy elementary particles, created when cosmic rays fall from space. They are ubiquitous in the atmosphere and can pass through nearly anything harmlessly. About 100,000 particles pass through the human body in just a few seconds. Their paths can be shifted very slightly by large natural forces, including tsunamis.

The detector is about 2m long in the tunnel under Tokyo Bay.

To detect the movement of muons, humans need an extremely sensitive instrument, such as the TS-HKMSDD detector in Tokyo Bay, Japan. The device is installed inside the Tokyo Bay Aqua-Line expressway tunnel. New research shows that TS-HKMSSD has for the first time detected a tsunami through oscillating muons. The detection happens in real time and is proven to be highly accurate.

"TS-HKMSSD is the world's first underwater muon observatory, and it detected changed muon activity during a tsunami. This change corresponds to ocean rise measured by methods "Combining these results means we can use muon data to accurately model changes in sea level, ignoring other methods that have drawbacks," said geophysicist Hiroyuki Tanaka. at the University of Tokyo said.

Other methods include tide gauges, buoys, aerial satellite imagery, and a variety of marine sensors. However, the muon tracking method promises to be faster, cheaper and easier to maintain than the above methods.

New research demonstrates how the TS-HKMSDD system detected a mild tsunami that swept across Tokyo Bay in September 2021 as a result of a typhoon approaching Japan from the south. As the ocean fluctuates, the number of muons varies slightly, dispersed by volume of water.

The team proposes to install devices similar to TS-HKMSSD in other tunnels in tsunami-prone areas and to use the same devices as tide gauges, becoming part of the system. early warning. "Thanks to the success of early tests like this, a number of similar systems have also been tested in the UK and Finland," Tanaka said.

The muon detectors that make up the TS-HKMSSD system are quite small, only about 2 meters long. Currently, 20 such detectors are located along the tunnel under Tokyo Bay. In addition to detecting incoming tsunamis, such a system could be used to search for natural gas reserves and detect ancient earthquake patterns.

For now, the team is delighted to be using the TS-HKMSSD as an accurate tsunami detector. In the future, it is possible that the system will help warn experts about natural disasters. "As far as I know, this tunnel is the first working national road in the world to be identified as a laboratory," Tanaka said.