The coastlines around the Indian Ocean are probably the areas most prone to tsunamis, besides the Ring of Fire. The largest earthquakes, and the tsunamis that sometimes occur with them, occur at subduction zones where an oceanic tectonic plate is sinking beneath another plate. Subduction occurs at many places around the Pacific ocean, but also under Indonesia in the Indian Ocean. The Indonesian subduction zone caused the 2004 Sumatra earthquake and tsunami, which killed hundreds of thousands of people. Tsunamis are unlikely to occur in places like the Atlantic Ocean, where there are no subduction zones except for in the Caribbean and Scotia seas.

The Ring of Fire is a zone of plate motion, specifically ocean plates sliding underneath continents, which periodically cause large earthquakes, and, thus, large tsunamis. However, anywhere that has that kind of plate motion can cause large earthquakes off the coast, which in turn make tsunamis. For example, the 2004 Sumatra earthquake happened in the Indian Ocean, outside of the traditional Ring of Fire, and caused a bad tsunami.