What percentage of tsunamis are caused by underwater earthquakes?

About 80% of tsunamis are caused by underwater earthquakes.

This figure is an approximate global statistic, not a fixed physical law. NOAA’s Global Historical Tsunami Database reports that more than 80% of likely tsunamis since 1900 were generated by earthquakes. The most dangerous earthquake-generated tsunamis usually begin when a large, shallow earthquake abruptly raises or lowers the seafloor.

That vertical displacement moves the water column above it and sends long waves across the ocean. Earthquakes at subduction zones, where one tectonic plate dives beneath another, are especially effective tsunami generators. The 2004 Indian Ocean tsunami and the 2011 Tōhoku tsunami in Japan were major examples.

The remaining events have other causes, including underwater landslides, volcanic eruptions, atmospheric disturbances, and—in theory—large impacts. Some earthquakes trigger landslides that contribute to the tsunami, so classifications can vary depending on whether researchers count the earthquake, the landslide, or both as the primary cause.