In which ocean do most earthquakes occur?

Most earthquakes occur in the Pacific Ocean. Its margins form the Pacific Ring of Fire, a horseshoe-shaped belt where tectonic plates collide, slide past one another, and plunge beneath other plates.

About 90% of the world's earthquakes occur within this belt, which stretches roughly 25,000 miles around the Pacific basin. Subduction zones along the coasts of South America, North America, Asia, and Oceania generate frequent earthquakes, including many of the planet's most powerful events.

The ocean itself is not causing the earthquakes; the key factor is the active plate boundaries surrounding it. This is also why the Pacific rim has so many volcanoes and deep ocean trenches. A common mix-up is confusing the Pacific Ring of Fire with a single fault. It is actually a broad network of different plate boundaries and faults.