TOKYO - The powerful earthquake that struck Kumamoto Prefecture on July 28 was caused by essentially the same mechanism as the devastating earthquakes that hit the region 10 years ago, according to a leading seismologist, who warned residents to prepare for strong aftershocks and take precautions against heatstroke even during the night.
The latest earthquake registered the maximum seismic intensity of 7 on Japan's scale and occurred along the Hinagu Fault Zone, a major fault system running through the region.
Junichi Nakajima, a professor at the Institute of Science Tokyo, said the earthquake was a strike-slip event that occurred slightly south of the area affected by the 2016 Kumamoto earthquakes.
"The mechanism of this earthquake is basically the same as that of the earthquake 10 years ago," Nakajima said. "The previous earthquake occurred on the northern side of the fault zone, while this one occurred slightly farther south. It can be described as a shallow inland earthquake directly beneath the area."
The epicenters of the latest earthquake and the 2016 disaster are only about 20 kilometers apart, leading some researchers to suspect that the two events may be connected.
However, Nakajima said further analysis would be required to determine whether stress changes caused by the earlier earthquake contributed to triggering the latest one.
"Some researchers believe the earthquakes may be related to each other," he said. "But we will need to examine the data carefully to understand how the earthquake 10 years ago may have induced this one."
Seismic activity had remained elevated south of the Hinagu Fault Zone since the 2016 earthquakes, with numerous smaller tremors occurring near the source area of the latest quake.
Nakajima said researchers had been aware that earthquake activity appeared to be particularly active in the southern part of the fault zone, although the occurrence of such a large earthquake there was still surprising.
"We had sensed that seismic activity was continuing in the southern area," he said. "Even so, I was surprised that an earthquake of this magnitude occurred at this location."
Nakajima urged residents to remain alert for aftershocks, including potentially strong tremors capable of breaking windows or causing dishes and furniture to fall.
He advised people to check for unstable objects around sleeping areas and to keep shoes or slippers beside their beds to avoid injury from broken glass or debris during a nighttime aftershock.
Residents should also prepare emergency backpacks or other essential supplies so they can evacuate quickly if necessary, he said.
Because darkness can increase fear and make evacuation more difficult during an earthquake, Nakajima recommended leaving a small light on overnight where possible.
He also emphasized the risk of heatstroke as Kumamoto experiences extremely hot summer conditions.
Residents with electricity and access to air conditioning should continue using it during the night, while those affected by power outages may consider moving to an evacuation center after daylight on July 30, provided it is safe to remain at home overnight.
"Heatstroke precautions are necessary even at night," Nakajima said. "If electricity is available and air conditioning can be used, that should not be a problem. If there is a power outage, evacuating to a shelter after it becomes light may be one option."
Source: FNN
