Undersea detector proves it's swell
A first-of-its-kind cosmic ray sensor successfully observes tsunami waves


Date:
April 13, 2022
Source:
University of Tokyo
Summary:
Highly energetic particles called muons are ever present
in the atmosphere and pass through even massive objects
with ease. Sensitive detectors installed along the Tokyo Bay
tunnel measure muons passing through the sea above them. This
allows for changes in the volume of water above the tunnel to be
calculated. For the first time, this method was used to accurately
detect a mild tsunami following a typhoon in 2021.



FULL STORY ========================================================================== Highly energetic particles called muons are ever present in the atmosphere
and pass through even massive objects with ease. Sensitive detectors
installed along the Tokyo Bay tunnel measure muons passing through the
sea above them.

This allows for changes in the volume of water above the tunnel to be calculated. For the first time, this method was used to accurately detect
a mild tsunami following a typhoon in 2021.


==========================================================================
In the time it takes you to read this sentence, approximately 100,000 muon particles will have passed through your body. But don't worry, muons pass through ordinary matter harmlessly, and they can be extremely useful too.

Professor Hiroyuki Tanaka from Muographix at the University of Tokyo
has made his career out of exploring applications for muons. He's
used them to see inside volcanoes and even detect evidence of ancient earthquakes. Recently, Tanaka and his international team of researchers
have turned their focus to meteorological phenomena, in particular,
tsunamis.

In September 2021, a typhoon approached Japan from the south. As it
neared the land it brought with it ocean swells, tsunamis. On this
occasion these were quite mild, but throughout history, tsunamis have
caused great damage to many coastal areas around Japan. As the huge
swell moved into Tokyo Bay, something happened on a microscopic level
that's almost imperceptible. Atmospheric muon particles, generated by
cosmic rays from deep space, were ever so slightly more scattered by
the extra volume of water than they would be otherwise. This means the
quantity of muons passing through Tokyo Bay varied as the ocean swelled.

"The Tokyo-bay Seafloor Hyper KiloMetric Submarine Deep Detector
(TS-HKMSDD) is the first underwater muon observatory in the world, and it detected varying muon activity during the tsunami," said Tanaka. "This variation corresponds to the ocean swells which were measured by other
methods. Combining these readings means we can use muographic data to accurately model changes in sea level, bypassing other methods which
come with drawbacks." There are other ways to measure changes in
sea level, with physical mechanisms such as tide gauges, satellites,
buoys, or sensors on the sea floor itself. But the TS-HKMSDD and future instruments based on it, installed in undersea tunnels, can be cheaper
to build and run, easier to access, and they don't suffer from physical
wear and tear as they have no moving parts. Critically though, the data
from TS-HKMSDD is both real time and highly accurate, two key criteria
that could make it suitable for a reliable early warning system.

"Thanks to the success we've had from early tests such as this,
similar systems are already being trialed in the U.K. and Finland," said Tanaka. "Obviously, an undertaking like this comes with challenges and installing delicate instruments in a busy tunnel could be difficult. But
we are grateful for the cooperation of the agencies responsible for
the Tokyo Bay tunnel. To the best of my knowledge, the tunnel is now
the first active national road in the world defined as a laboratory."
Tanaka and his team have many other ways in store to make use of muons, including a possible way to accurately synchronize time around the world,
and, related to that, a spatial positioning system far more accurate
than current GPS.


========================================================================== Story Source: Materials provided by University_of_Tokyo. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Hiroyuki K. M.Tanaka, Masaatsu Aichi, Szabolcs Jo'zsef Balogh,
Cristiano
Bozza, Rosa Coniglione, Jon Gluyas, Naoto Hayashi, Marko Holma,
Jari Joutsenvaara, Osamu Kamoshida, Yasuhiro Kato, Tadahiro Kin,
Pasi Kuusiniemi, Giovanni Leone, Domenico Lo Presti, Jun Matsushima,
Hideaki Miyamoto, Hirohisa Mori, Yukihiro Nomura, Naoya Okamoto,
La'szlo' Ola'h, Sara Steigerwald, Kenji Shimazoe, Kenji Sumiya,
Hiroyuki Takahashi, Lee F. Thompson, Tomochika Tokunaga, Yusuke
Yokota, Sean Paling, Dezső Varga. Periodic sea-level
oscillation in Tokyo Bay detected with the Tokyo-Bay seafloor
hyper-kilometric submarine deep detector (TS-HKMSDD).

Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-10078-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413104201.htm

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