A magnitude 6.3 earthquake struck the Bonin Islands, also known as the Ogasawara Islands, in Japan on the Richter scale, alarming residents of the area. Security forces and local officials were placed on alert as soon as news of the quake emerged. Details on any damage have yet to be confirmed.
The impact of an earthquake depends not only on its magnitude but also on its depth, its distance from populated areas and the quality of local construction. A deep quake can register a high magnitude yet cause little damage at the surface.
The Earth’s crust is divided into seven major tectonic plates and several smaller ones, which move slowly and constantly. As their edges collide or grind against one another, stress builds up along the boundaries. When that stress exceeds what the rock can withstand, it ruptures, releasing stored energy as seismic waves. When those waves reach the surface, the ground shakes.
Quakes below magnitude 2.0 are classed as micro-earthquakes and are rarely felt. Those at 4.5 and above can be felt over wide areas and may cause minor damage near the epicentre. Earthquakes of magnitude 7.0 or higher are considered major and can bring building collapses and heavy casualties.