The were a series of earthquakes, including a magnitude 7.0 mainshock which struck at 01:25 JST on April 16, 2016 (16:25 UTC on April 15) beneath Kumamoto City of Kumamoto Prefecture in Kyushu Region, Japan, at a depth of about , and a foreshock earthquake with a magnitude 6.2 at 21:26 JST (12:26 UTC) on April 14, 2016, at a depth of about .
In total, the two earthquakes killed 273 people and injured 2,809 others, a majority of them indirectly. Severe damage occurred in Kumamoto and Ōita Prefectures, with numerous structures collapsing and catching fire. More than 44,000 people were evacuated from their homes due to the disaster.
Earthquakes
April 14 foreshock
Although the focus of the foreshock earthquake was beneath Mount Kinpo to the north-northwest of Kumamoto's city center, the worst-hit area was in the eastern Kumamoto suburb of Mashiki, where the foreshock earthquake's victims perished. The earthquake was strongly felt as far north as Shimonoseki on southwestern Honshu, and as far south as the city of Kirishima in Kagoshima Prefecture. In the following hours, there were at least 11 aftershocks of at least 4.5 magnitude, one of which was a magnitude 6; more than 140 aftershocks were registered within two days. It was the first earthquake to occur on the island of Kyushu to register as a 7 on the Japan Meteorological Agency seismic intensity scale. On April 15, the JMA officially labelled it (, "Heisei 28 Kumamoto Earthquake")–Heisei 28 being the year 2016 on the Japanese calendar.
April 16 mainshock
At 01:25 JST on April 16 (16:25 UTC, April 15), a 7.0 magnitude earthquake, under Higashi Ward of Kumamoto City in the Kyushu Region in southwest Japan, occurred as the result of strike-slip faulting at shallow depth. Significant additional damage occurred in those areas of Kumamoto Prefecture recovering from the April 14 earthquake, with strong tremors and damage also recorded as far east as the city of Beppu in Ōita Prefecture. It was also felt as far away as Busan, South Korea, with an intensity of MMI III. A tsunami advisory was issued at 01:27 JST for areas along the Ariake Sea and Yatsushiro Sea, with the wave height forecast at , but was lifted less than an hour later at 02:14 JST.
Aftershocks
The following is a list of major aftershocks that have occurred in Kumamoto Prefecture since April 14, 2016.
Damage and casualties
As a result of the tremors, the entirety of Kumamoto city was left without water. All residents of Nishihara Village in Kumamoto Prefecture were evacuated over fears that a nearby dam could collapse. Kumamoto Airport was also closed to all but emergency flights, and service on the Kyushu Shinkansen was suspended after a train derailed due to the earthquake. Numerous structures collapsed or caught fire as a result of the earthquake. Government officials estimated more than 1,000 buildings had been seriously damaged, with 90 destroyed. A 500-bed hospital in Kumamoto City was knocked off its foundations, forcing the evacuation of all patients, and a natural gas leak prompted Saibu Gas to turn off supplies to multiple homes in the city.
Numerous landslides took place across the mountains of Kyushu, rendering roads impassable, The of the Japan National Route 325 in Minamiaso collapsed into the Kurokawa river. A particularly large rockslide was photographed blocking the entirety of a four-lane express-way close to the fallen Great Aso Bridge, leaving a large scar that ran almost completely up the hill that suffered the rockslide.
The Aso Shrine was also heavily damaged in the earthquake. The shrine's rōmon (tower gate), officially classified as an Important Cultural Property by the Japanese government, and the haiden (worshiping hall) both completely collapsed. Kumamoto Castle, another Important Cultural Property sustained damage to its roof and exterior buildings and walls because of the earthquakes and associated aftershocks. Several of the castle's shachihoko ornaments were destroyed, and a large number of kawara tiles also fell from the roof. Other historical buildings such as Janes' Residence, the first western-style house built in Kumamoto (dating from 1871) were also totally destroyed. The former registered Cultural Asset was initially located in the grounds of Kumamoto Castle, but was later relocated near Suizen-ji Jōju-en.