Bridges Down, Kumamoto Castle Damaged — Remembering the 2016 Kumamoto Disaster

A violent tremor struck along with a grinding sound

What did FRIDAY report 10, 20, or 30 years ago? In this installment of “Playback Friday,” we revisit topics that made headlines at the time. This time: the May 6, 2016 issue article, “Was the M7.3 Kumamoto Earthquake the Beginning of an Even Greater Fear?”

At 9:26 p.m. on April 14, 2016, a major earthquake measuring magnitude 6.5 struck the Kumamoto region of Kumamoto Prefecture, registering a maximum intensity of 7 in Mashiki. By the evening of the following day, April 15, the disaster had already caused nine deaths, power outages affecting 12,300 households, and water outages affecting 80,500 households. However, just 28 hours later, an even more destructive main shock

A reporter from the magazine who experienced the main shock firsthand described the moment in the article:

“At 1:25 a.m. on April 16, while sleeping at a hotel in Kumamoto, this reporter was jolted awake by a powerful upward thrust. The next instant, a huge tremor hit together with a grinding sound — gori. A canned coffee sitting on the table and a 30-inch television on a shelf came crashing down one after another.

When the shaking subsided and I made my way down the emergency staircase to the lobby, water was spraying from the ceiling. It seemed the building’s water tank had burst, and from the dining hall next to the lobby came the sound of water pouring down like a waterfall.”

When day broke, Kumamoto City was littered with destruction: signs had fallen throughout shopping streets, and rubble was scattered everywhere. At Kumamoto Castle, two turrets designated as Important Cultural Properties had collapsed along with their stone foundations. Meanwhile, the famous soapland establishment Blue Chateau escaped structural collapse, but many interior fixtures, including mirrors, were destroyed.

The magazine reporter then traveled about 30 minutes by car from central Kumamoto City to cover conditions in Mashiki Town, located in Kamimashiki District. The town had already suffered severe damage from the April 14 quake, and the second earthquake only worsened the devastation into a horrifying scene.

“Many homes had their first floors crushed, traffic lights leaned over, and some roads had sunk several meters. Twenty people had died. Around 2,000 buildings were damaged. Even the road leading farther on to Minamiaso Village, about 40 minutes by car from Mashiki, was cracked in many places. In the village, numerous buildings had been swallowed by landslides, Aso Bridge had collapsed, and roads connecting to the village center had been severed, leaving many disaster victims isolated. We spoke to a man who had returned to check on his home.

‘I was okay, but my mother, who was sleeping at home, was injured after being crushed by a shelf. The hospitals weren’t functioning because of the blackout, so all she could get were painkillers — she couldn’t be admitted. The evacuation shelters were also full, so we couldn’t get in. My mother still has three broken ribs, and we’re living together in our car.’”

After April 14, Kumamoto Prefecture experienced more than 700 earthquakes registering at least intensity 1 within a single week. Another quake measuring lower 5 on the Japanese seismic scale struck on the evening of April 19. People were left with growing anxiety as the relentless earthquakes showed no sign of ending.

Anxiety caused by the unsettling activity of active fault lines

The earthquakes ultimately claimed 278 lives — including 50 direct deaths and 228 disaster-related deaths — while 8,667 homes were completely destroyed and 183,882 people were evacuated. Attention focused particularly on the fact that roughly 80% of the deaths were disaster-related, caused in part by the confusion at evacuation centers immediately after the disaster. Care for evacuees forced to sleep in their cars also became a major issue.

After the main shock on April 16, the area experiencing frequent earthquakes expanded in a 150-kilometer belt stretching from around Kumamoto to the Aso region and even into central Oita Prefecture. The Japan Meteorological Agencyofficially named the series of seismic events beginning on April 14 the “2016 Kumamoto Earthquakes.” Although seismic activity gradually subsided, approximately 4,000 aftershocks registering at least intensity 1 occurred by April 2017 — far exceeding the 999 aftershocks recorded after the inland Niigata Chuetsu Earthquake.

It was an unprecedented earthquake in several respects: never before in recorded history had the same location experienced seismic intensity 7 twice, with the second quake larger than the first. It was also the first time seismic intensity 7 had ever been recorded in Kyushu.

Ten years have passed since the disaster, and reconstruction has steadily progressed in the affected areas. Kumamoto Castle — one of the most symbolic sites damaged by the earthquake — saw its main keep and long wall restored in 2021. Visitor numbers, which had once fallen to 120,000, have recovered to 1.42 million, nearly back to pre-earthquake levels. However, restoration work on the castle’s turrets and stone walls remains unfinished. In particular, more than 100,000 stones still need to be carefully reassembled, meaning the process will take many more years. Full restoration is currently scheduled for fiscal 2052.

The Kumamoto Earthquakes are believed to have been caused by movement along the Hinagu Fault Zone and the Futagawa Fault Zone, which extends southwest of Kumamoto City. One scholar specializing in crustal movement pointed out that the quake may have been linked to activity along the Median Tectonic Line fault zone, which stretches from Kashiba in Nara Prefecture to offshore Iyo. In fact, on September 1, 1596, the Keicho Bungo Earthquake (M7.0) struck Oita Prefecture, connected to the western side of the Median Tectonic Line fault zone. Four days later, the Keicho Fushimi Earthquake (M7.5) struck the Kansai region on the eastern side of the same fault system.

Another seismologist had previously predicted that, as a precursor to a future Nankai Trough Earthquake, stress would accumulate along old inland active faults, triggering several earthquakes. Among the faults he identified were the Hinagu Fault Zone responsible for the Kumamoto Earthquakes, the area from central Kii Peninsula westward to Wakayama along the Median Tectonic Line fault zone, and the eastern edge fault zone of the Nara Basin. Supporting this theory, on April 1, 2016, an earthquake registering a maximum seismic intensity of 4 struck Wakayama Prefecture at the eastern end of the Median Tectonic Line.

Although experts say there is no direct connection between the Kumamoto Earthquakes and a future Nankai Trough megaquake, some argue that the occurrence of earthquakes caused by active faults is itself evidence that a Nankai Trough event may be approaching. Nine years after the aforementioned Keicho Bungo Earthquake, the massive Keicho Earthquake — centered in the Nankai Trough — occurred.

Even ten years after the Kumamoto disaster, we must not forget that another major earthquake could strike at any time — even tomorrow.

A landslide struck Minamiaso Village during the main shock on April 16, 2016. Even during the search efforts on the 19th, three people remained unaccounted for (from the May 6, 2016 issue)