Experts Suspect Japan's M7.1 Quake Triggered by Pressure on Old Fault
Jakarta (ANTARA) - A powerful earthquake that shook south-western Japan on Tuesday is believed to have been triggered by the slippage of a fault section that did not rupture when twin quakes struck the same region a decade ago.
Experts have warned that strong aftershock activity could still continue, Kyodo news agency reported on Tuesday.
The latest quake, centred in Kumamoto Prefecture with a magnitude of 7.1, occurred not far from the epicentre of a similar inland earthquake of magnitude 6.5 on 14 April 2016, and a magnitude 7.3 quake two days later.
All three earthquakes registered the highest seismic intensity level, level 7 on the Japanese scale, in several areas of the prefecture.
The 2016 earthquakes devastated the region and killed more than 270 people.
A number of active fault zones, including the Hinagu and Futagawa fault zones that triggered the 2016 quakes, stretch across central Kyushu.
Experts have repeatedly cautioned that the southern section of the Hinagu fault zone—which extends to the nearby Yatsushiro Sea—hardly shifted at all following the earthquake ten years ago.
Shinji Toda, a professor of seismology at Tohoku University, found that the number of earthquakes of magnitude 1.5 or greater has more than doubled compared with the period before the 2016 quake.
The finding was based on an analysis of seismic activity near the Hinagu fault zone over the past decade.
Toda explained that the 2016 earthquake is believed to have generated enormous stress and pressure, which ultimately caused movement along the Hinagu fault zone this time.
He added that the two events share the same triggering mechanism.
According to the Japan Meteorological Agency, Tuesday’s quake, which struck at 4.27 pm local time, occurred at a depth of 16 kilometres along a strike-slip fault—a condition in which two adjacent plates slide horizontally past each other, similar to the characteristics of the 2016 earthquake.
Nevertheless, the Japan Meteorological Agency has so far not explicitly linked Tuesday’s earthquake to the series of major quakes that occurred a decade ago.
Source: Kyodo