Submarine earthquake

The Earth's surface or lithosphere comprises tectonic plates which average approximately 80 km (50 mi) in thickness, and are continuously moving very slowly upon a bed of magma in the asthenosphere and inner mantle.

Some of the main areas of large tsunami-producing submarine earthquakes are the Pacific Ring of Fire and the Great Sumatran fault.

There is an interplay of various densities of lithosphere rock, asthenosphere magma, cooling ocean water and plate movement for example the Pacific Ring of Fire.

In the gap, thus produced hot magma rises up, meets the cooler sea water, cools, and solidifies, attaching to either or both tectonic plate edges creating an oceanic spreading ridge.

If the fissure is able to come apart because of the two plates moving apart, in a sudden movement, an earthquake tremor may be felt for example at the Mid-Atlantic Ridge between North America and Africa.

A 2019 study based on new higher-resolution data from the Transportable Array network of USArray found that large ocean storms could create undersea earthquakes when they passed over certain areas of the ocean floor, including Georges Bank near Cape Cod and the Grand Banks of Newfoundland.