[3][4] The MTL begins near Ibaraki Prefecture, where it connects with the Itoigawa-Shizuoka Tectonic Line (ISTL) and the Fossa Magna.

It runs parallel to Japan's volcanic arc, passing through central Honshū to near Nagoya, through Mikawa Bay, then through the Inland Sea from the Kii Channel and Naruto Strait to Shikoku along the Sadamisaki Peninsula and the Bungo Channel and Hōyo Strait to Kyūshū.

[5] The upper part of the Japanese islands was created at the edge of the Eurasian plate 180 million years ago.

[7] It caused approximately ten trillion yen ($100 billion) in damage, 2.5% of Japan's GDP at the time.

In the central Kanto Plain, boring tests have shown that the MTL lies 3000 meters beneath ground level in Saitama Prefecture.

It is not clear where the MTL goes from there, but it is thought that it passes beneath Kashima or Ōarai on the Pacific coast in Ibaraki Prefecture.

However, because the Ōno River basin south of Ōita is covered by late Mesozoic sedimentary rock, the geological continuity in the westward direction is unclear.

[8] After crossing the Hōyo Strait from Kyushu to Shikoku, the MTL passes north of the Sadamisaki Peninsula to land at Iyo on the west coast of Ehime Prefecture.