TOKYO - Ten years ago, Kumamoto Prefecture was jolted by two earthquakes that registered the maximum level of 7 on Japan's seismic intensity scale, triggered by moves of the northern edge of the Hinagu fault zone and the Futagawa fault zone.
The latest magnitude 7.1 quake on July 28 this year, which also measured level 7, is said to have originated from a more southerly section of the Hinagu fault than in 2016.
Based on the quake's scale and the pattern of aftershocks, seismologists believe not all of the Hinagu fault zone has ruptured and some segments remain, meaning preparations should continue for another major earthquake.
Damage to buildings appears relatively limited for the level of shaking, likely because many seismically weak structures collapsed in the temblors in 2016 or were repaired and retrofitted afterward, underscoring again the importance of improving quake resistance.
On some expressway sections, damaged bridges forced closures, likely due to strong temblor or fault displacement.
The 1995 earthquake that rattled Kobe in western Japan toppled elevated structures on the Hanshin Expressway and knocked down bridge girders, and countermeasures such as strengthening bridge piers and wiring girders to prevent falls have been adopted.
Whether those measures proved effective this time needs to be reviewed, as expressways serve as a last line for emergency transport and relief logistics after major quakes. Considering a potential Nankai Trough megaquake, Japan should consider building in greater safety margins for routes such as the Shin-Tomei Expressway in Shizuoka Prefecture.
At the Nippon Paper Industries Co. plant in Yatsushiro, Kumamoto Prefecture, several smokestacks were damaged including one that collapsed. Its location near the mouth of the Kuma River on potentially unstable ground may have amplified the shaking.
Many manufacturing factories built since Japan's high-growth era stand on soft ground, including reclaimed land, and may also be aging. The central government should order a comprehensive inspection to confirm whether adequate seismic measures are in place.
At the Aeon Mall Kumamoto in Kashima, Kumamoto Prefecture, an explosion is believed to have occurred after the quake due to a liquefied petroleum gas leak.
For natural gas, systems exist to automatically halt the supply when shaking exceeds a certain level.
In the case of the Aeon shopping mall, the cause of the explosion must be clarified quickly, including what earthquake countermeasures were in place and whether they functioned correctly.
At the same time, the central government should survey actual liquefied petroleum gas use to confirm its safety at other large facilities that draw big crowds, and it should also check gas safety measures for earthquakes as well as evacuation guidance including calls to head outdoors as soon as the shaking subsides.
Three hospitals, including Kumamotominami Hospital in Uki, suffered major damage, prompting inter-hospital transfers in which other hospitals took in inpatients. We must not forget that the burden of moving patients can worsen their condition and lead to disaster-related deaths.
While hub hospitals, which accept emergency patients, have advanced anti-quake measures, it is necessary to investigate whether other hospitals are sufficiently prepared.
While the shaking continues and there is the possibility of another major quake, people should avoid sheltering at home with tilted structures or fallen walls. With power outages leaving some evacuation centers unable to secure adequate air conditioning, many may feel compelled to sleep in cars to prevent heatstroke.
To avoid so-called economy-class syndrome caused by poor circulation, people should continue taking protective steps such as doing light exercises and stretching from time to time.
Nobuo Fukuwa, born in Nagoya in 1957, is professor emeritus at Nagoya University. He completed graduate studies at the university, worked for a major general contractor and joined Nagoya University in 1991. He served as the head of the university's Disaster Mitigation Research Center from 2012 to 2021 and specializes in earthquake engineering.
