(NewsNation) — In an area familiar with devastation from earthquakes and tsunamis, there were some nervous hours Wednesday after a powerful 7.4 earthquake struck off the coast of Fukushima, Japan.

Four people died and more than 90 others were injured in the quake. More than 2 million homes across the region lost power as residents braced for possible aftershocks and kept watch for a potential tsunami. This was just another shake for the area hit by a 9.1 quake that caused a devastating 45-foot-high tsunami that led to disaster at the Fukushima nuclear plant 11 years ago.

Wednesday’s quake was followed by several aftershocks, which NewsNation meteorologist Gerard Jebaily explained came because of Japan’s unique position on the planet. It sits at the congruence of four tectonic plates, the North American plate, the Pacific plate, the Eurasian plate and the Philippine Sea plate. These plates “float” on the molten material below them and their movement causes earthquakes and volcanoes.

Japan sits on the western edge of what’s known as the “Ring of Fire,” an area of high seismic activity that spans the Pacific Ocean from the coasts of North and South America, across the northern polar regions and back down through Japan and the Philippines before ending east of Australia. Essentially, Mount St. Helens in Washington State and the Fukushima disaster were spurred by the same geological instability.

A tsunami is caused when two plates rub against each other and one rises or falls abruptly, displacing a massive amount of water and causing a wave. When the wave gets to the shallower water near a body of land, its full size emerges and disaster ensues. Fortunately, the tsunami produced by the latest quake was only 3 feet tall.