Japan Atlas: Architecture 
Seikan Submarine Tunnel

Construction started: 
September 1971 

 Railway opening: 
March 1988 

 Total length: 
53.85 km (33.5 mi) 

 Length undersea: 
23.3 km (14.5 mi) 

 Deepest point: 
240 m (787 ft) below sea level. 

 Internal height: 
7.85 m (25.8 ft) 

 Internal width: 
9.7 m (31.8 ft) 



The Longest Railway Tunnel Ever Constructed Beneath a Seabed  

The Seikan Submarine Tunnel was opened in March 1988 and runs beneath the seabed of the Tsugaru Strait, which separates the southern edge of Hokkaido from Aomori Prefecture on the northern edge of the mainland. This tunnel is a part of a railway that runs between Aomori City and Hakodate City in just two and a half hours, and was named by combining the two characters and pronunciations of Aomori City's "Ao (Sei)" and Hakodate City's "Hako (Kan)". The length of 53.85 kilometers (33.5 miles) makes it world's longest, though its 23.3 kilometers (14.5 miles) of submarine portion was outdistanced by the 37.5-kilometer (23.3-mile) Euro Tunnel which opened in 1994. The railway track runs 240 meters (787 feet) below the sea surface, and is the deepest railway line in the world. The advanced civil engineering technologies have been rated highly that made it possible for the tunnel to run below 140-meter-deep (459-foot-deep) water as well as 100 meters (328 feet) below the seabed.  

The tunnel was designed with gentle curves and slopes for possible future use by Shinkansen (bullet trains). In addition, high-strength rails suitable for Shinkansen (bullet trains) have been used. 

There are two stations inside the tunnel: Tappi Kaitei Station on the Aomori side, and Yoshioka Kaitei Station on the Hokkaido side. They are both located just under the coastal line. In these two station buildings-which are rare submarine stations-tour courses have been established with reference displays of the Tsugaru Strait and the Seikan Tunnel.  

Photo: An express train running out of Seikan Tunnel (Ministry of Foreign Affairs)  

Unauthorized reproduction of the photos in this page is prohibited. 

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