How large an earthquake can Nankai Trough produce?

The maximum magnitude potential compiled for Nankai Trough is M8.8. That figure comes from the length and width of the fault area that could rupture at once, calibrated against its historical and paleoseismic record. It is an upper bound on what the structure can do, not a forecast of the next event.

Is Nankai Trough overdue for an earthquake?

No fault is ever 'overdue' in the way the phrase suggests. Recurrence intervals are averages over a handful of past ruptures, not a schedule: the interval between two events on the same fault routinely varies by a factor of two or more. The elapsed time shown on this page is exactly that — how long it has been — and not a probability that a rupture is imminent.

How is the seismicity on this page selected?

Every earthquake listed sits within 25 km of the mapped trace of Nankai Trough, measured as the distance to the nearest fault segment rather than to a bounding box. Events on a neighbouring structure therefore do not appear here, even when they are geographically close. The slip rate of 40–50 mm/yr and the rupture history are compiled from the published literature.

All fault systems

Subduction megathrust

Nankai Trough

Southwestern Japan

Plate boundary: Philippine Sea ↔ Eurasian

Length: 700 km
Mₘₐₓ potential: M8.8
Slip rate: 40–50 mm/yr
Recurrence interval: ~120 years

Time elapsed since the last known rupture

67%

80 years have passed against an average interval of about 120 years. Recurrence on a real fault is not a clock — this is elapsed time, not a probability of rupture.

Locking depth

5–30 km

The depth range over which the fault is locked and accumulating elastic strain. Below it the rock creeps aseismically; above it, strain is released in earthquakes.

Historical rupture sequence

1946M8.1Nankaidō
1944M8.1Tōnankai
1707M8.6Hōei

Live seismicity within 25 km of the trace (last 30 days)

Loading seismicity along this fault trace…

Frequently Asked Questions (FAQ)

Verified scientific, operational, and emergency protocols

Nankai Trough is a subduction megathrust system running roughly 700 km through Southwestern Japan. The kinematics describe how the two sides move relative to each other, which governs both the shaking a rupture produces and whether it can displace the sea floor.