How do earthquakes cause tsunamis?

Earthquakes generate tsunamis through underwater tectonic activity that results in the sudden rise or fall of the sea floor. This movement displaces a large volume of water in an ocean or large lake, creating a series of long-wavelength waves known as a tsunami wave train. While tectonic plate movements are a primary cause, other disturbances like landslides and volcanic eruptions can also displace water to create giant waves.

What we know

• Ordinary tsunamis are caused by underwater tectonic activity along plate boundaries, resulting from earthquakes and the subsequent rise or fall of the sea floor that displaces a volume of water. [2, 3]
• Submarine earthquakes were suggested to be related to tsunamis as early as the 5th century BC by the Ancient Greek historian Thucydides. [2]
• The 2011 Tōhoku earthquake was an undersea megathrust earthquake that triggered powerful tsunami waves reaching heights of up to 40.5 meters in Miyako. [5]

Still open

• Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do.

Where to go next

• how it workedWhat is a megatsunami and how does it form?
• a case in pointHow did the 2011 Tōhoku earthquake happen?
• the bigger pictureWhat are natural disasters caused by displacement?
• what caused itHow do volcanic eruptions trigger giant waves?
• what followedWhat was the historical impact of the 2004 Indian Ocean tsunami?
• an unexpected connectionHow can a dam collapse cause a massive wave?Human activity destabilizing the sides of a valley can trigger landslides into reservoirs, creating destructive waves comparable to natural megatsunamis.

Sources

• [1]tsunami (Wikidata Q8070) · CC0 1.0
• [2]Tsunami · CC BY-SA 4.0
• [3]Megatsunami · CC BY-SA 4.0
• [4]Cumbre Vieja tsunami hazard · CC BY-SA 4.0
• [5]2011 Tōhoku earthquake and tsunami · CC BY-SA 4.0