Tsunami Duration in the Pacific Ocean

Pacific tsunamis (mostly from subduction zone earthquakes) typically last:

• Wave Train Duration: Minutes to several hours. Multiple waves arrive at 10–60 min intervals.
• Longest Records: 1960 Chile (M9.5) – oscillations recorded >24 hrs in Hawaii/Japan. 2011 Tohoku (M9.1) – hazardous waves >12 hrs across Pacific.
• Local vs. Distant: Near-source: first wave in minutes, duration hours. Far-field: first wave hours later, but wave train still hours long.

Key Factors

• Earthquake magnitude/rupture length.
• Bathymetry (seafloor shape) – focuses/defocuses energy.
• Coastal geometry – harbors, bays trap oscillations (seiching).
• Aftershocks – can generate new wave trains.

Safety Rule: Stay away from coast for at least 24 hours after warning cancellation. Later waves can be larger.