Published : 04 Aug 2026, 01:37 AM
Updated : 08 Sep 2026, 09:30 AM
A 6.8-magnitude earthquake that hit Kumamoto in southwest Japan on Tuesday, killing 13 people and injuring hundreds, stemmed from an uncommon form of inland seismic movement, scientists say.
The quake struck Kyushu island at around 4:27pm local time, with its epicentre in Kumamoto Prefecture.
The shaking damaged public infrastructure and trapped shoppers at a mall in Kashima town after part of the building's second floor gave way, reports The Independent.
Japan sits where several tectonic plates meet and is crossed by numerous shallow faults, making it prone to frequent earthquakes.
The US Geological Survey (USGS) said this latest quake was caused by shallow strike-slip faulting, a mechanism distinct from the subduction-zone quakes that typically strike off Japan's eastern coast, where one plate is forced beneath another, often triggering major tremors, eruptions or tsunamis.
Tuesday's quake instead resulted from a thrust event, where one block of rock is pushed up and over another, seismologists Judith Hubbard and Kyle Bradley wrote in their newsletter Earthquake Insights.
Such quakes tend to be smaller than major subduction events but can cause intense shaking near population centres, they noted.
The rupture occurred several hundred kilometres northwest of the Ryukyu Trench, where the Philippine Sea plate begins sliding beneath Japan and the Eurasian plate.
USGS said the shallow depth and fault type point to activity within the upper Eurasian plate, with the Philippine Sea plate converging northwestward at 58mm a year.
Scientists cautioned that identifying the exact fault responsible would require field studies and satellite radar data collected over time, noting that Japan's inland faults form a complex network where large ruptures often involve multiple strands across a wide area.
