UPDATE 4:51 EST: The Japanese Meteorological Agency has issued a yellow-level tsunami warning for three regions including Tanegashima Yakushima areas, the Amami Islands and Tokara Islands area and the western part of Kagoshima Pref. The agency does not expect the tsunami to cause any damage if it reaches the coastal regions. The U.S. Geological Survey also downgraded the earthquake's strength to a 6.5 on the Richter magnitude scale, while the Japanese agency continues to list it at 7.0.
A magnitude 7.0 earthquake shook the southern coast of Japan Friday afternoon, according to the U.S. Geological Survey. The quake occurred 99 miles southwest from Makurazaki and 102 miles from Kaseda, and experts said there was no threat of tsunamis.
BREAKING: Magnitude 7.1 earthquake hits off southern coast of Japan.
— Reuters Top News (@Reuters) November 13, 2015
A magnitude 7.0 earthquake is classified as a major earthquake that can cause serious damage. Magnitudes measure the energy released at the source of the earthquake, which is determined from measurements on seismographs. After an earthquake, secondary shockwaves can occur, and while they are less violent than the main quake, they can still be strong enough to do additional damage to weakened structures. The aftershocks can occur within hours or even months after the initial quake. In coastal areas, there is also the possibility of tsunamis.