Abstract
Tidal measurements are of great significance since they may provide us with essential data to apply towards protection of coastal communities and sea traffic. Currently, tide gauge stations and laser altimetry are commonly used for these measurements. On the other hand, muography sensors can be located underneath the seafloor inside an undersea tunnel where electric and telecommunication infrastructures are more readily available. In this work, the world’s first under-seafloor particle detector array called the Tokyo-bay Seafloor Hyper-Kilometric Submarine Deep Detector (TS-HKMSDD) was deployed underneath the Tokyo-Bay seafloor for conducting submarine muography. The resultant 80-day consecutive time-sequential muographic data were converted to the tidal levels based on the parameters determined from the first-day astronomical tide height (ATH) data. The standard deviation between ATH and muographic results for the rest of a 79-day measurement period was 12.85 cm. We anticipate that if the length of the TS-HKMSDD is extended from 100 m to a full-scale as large as 9.6 km to provide continuous tidal information along the tunnel, this muography application will become an established standard, demonstrating its effectiveness as practical tide monitor for this heavy traffic waterway in Tokyo and in other important sea traffic areas worldwide.
Highlights
Tidal measurements are of great significance since they may provide us with essential data to apply towards protection of coastal communities and sea traffic
The Tokyo Bay Aqua-Line (TBAL), which is known as the Trans-Tokyo Bay Expressway, is a combined bridge and tunnel structure spanning the entire width of Tokyo Bay, Japan (Fig. 2)
TBAL consists of a 4.4-km long bridge (30% of TBAL) and a 9.6-km long tunnel (70% of TBAL) underneath the bay
Summary
Tidal measurements are of great significance since they may provide us with essential data to apply towards protection of coastal communities and sea traffic. This technique that combines the information about the predicted height of the satellite with geophysical corrections provides the reflecting point on the sea surface Such information has been used for monitoring sea level rise and geostrophic currents in the o cean[4]. GNSS satellite positioning technology, allowing us to distribute the tide gauges in the offshore region, and it can measure tidal level with high precision and relatively fast time resolutions (30 s–1 day)[5]. Ultrasonic gauges do not have to float on the sea surface, and there are no intrinsic drift errors either This technique measures the propagation time of the ultrasonic signals between the sea surface and the sensor located at the seafloor. Since muons propagate through solid and liquid materials in a similar manner, the sensors can be located underneath the seafloor; for example, muon detectors can be placed inside an undersea tunnel where electric and telecommunication infrastructures are convenient and well-arranged but often readily available and an important part of the original tunnel design
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