Japan Issues Its First 'Megaquake Advisory'

A quake on Thursday raises fears of potentially devastating Nankai Trough disaster
By Newser Editors and Wire Services
Posted Aug 9, 2024 12:56 PM CDT
'Megaquake Advisory' Rattles Japan
This aerial photo shows the site of a landslide in Shibushi, Kagoshima prefecture, southern Japan following Thursday's powerful earthquake.   (Kyodo News via AP)

Japanese Prime Minister Fumio Kishida canceled a planned trip to Central Asia on Friday to lead the government's response after scientists urged people to prepare for a possible "megaquake" off the country's southern coast. The Japan Meteorological Agency issued its first ever "megaquake advisory" on Thursday, warning of a possible major earthquake triggered by the underwater Nankai Trough, after a magnitude 7.1 quake shook just off the eastern coast of Kyushu island earlier in the day. The trough, which runs along Japan's Pacific coast, was the source of past devastating earthquakes, the AP reports.

Seismologists at the agency held an emergency meeting after Thursday's quake to analyze whether it had affected the nearby trough and reassessed the risk of a major quake. They urged people to observe high caution levels for about a week. Thursday's quake injured 16 people, most of them slightly, and caused no major damage. Tsunami advisories were issued for several areas but lifted hours later.

  • The Fire and Disaster Management Agency instructed 707 municipalities designated as at risk from a Nankai Trough quake to review their disaster response measures and evacuation plans.
  • The meteorological agency's first "megaquake advisory" sparked public unease and prompted local government offices, rail operators and other agencies to begin introducing precautionary measures, affecting holiday travelers during the summer "Obon" holiday week.
  • Kishida announced that he had canceled his planned Aug. 9-12 trip to Kazakhstan, Uzbekistan, and Mongolia as a result of the advisory. "I have decided to stay in the country at least for about a week to make sure that government measures and communication are fully in place," Kishida said.

  • Some municipalities closed parks or canceled events for the coming week, although officials and experts stressed that there was no need to shut down any normal activity. They said the advisory was aimed only at raising awareness of a increased probability over the long term, and that it was not for any specific timeframe or location.
  • In a 2013 report, a government disaster-prevention team said that if a magnitude 9.1 quake struck near the southern coast, it could generate a tsunami exceeding 33 feet with a death toll of more than 300,000 and economic damage of more than 220 trillion yen—$1.5 trillion—in a worst case scenario.
  • The Nankai Trough runs for around 600 miles off Japan's southwest Pacific coast and strains along the underlying fault "could result in a megaquake roughly once in 100 to 150 years," per Reuters. Quakes caused by the fault sometimes happen in pairs: The most recent was in 1946, two years after a 1944 quake.
(More Japan earthquake stories.)

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