Shinkansen lines cross active faults at 79 locations nationwide, and slippage at those crossings could damage the tracks above, according to NHK. The finding follows the July Kumamoto earthquake, when a fault's movement reached the surface and damaged the Kyushu Shinkansen line running directly overhead.
The line resumed service in September after repair work. Three months after the quake, gaps remain between bridge girders, the broadcaster reported.
An active fault — a fracture in the earth's crust where movement is expected — can shift during an earthquake and displace the ground on either side. Where a Shinkansen viaduct or bridge spans such a fault, the two sides can move apart or against each other, putting stress on the structure and the rails.
NHK reported that the 79 crossings have been identified across the country and that countermeasures are being sought for them.