Megaquake Warning Issued for Japan This Week — What Does This Dire Alert Signal?

A megaquake warning was issued in Japan this week. What precipitated the severe response, and how does a megaquake differ from more typical earthquakes? Read on for all of the details.

Japanese Officials Issue Rare Megaquake Warning

A strong 7.4 magnitude earthquake hit the island of Japan last Monday, April 20, prompting the government to issue a warning of a possible megaquake. At least 11 towns were told to evacuate and seek higher ground due to the threat of a tsunami.

And a magnitude 6.2 earthquake shook part of northern Japan early Monday, April 27, but there was no damage or casualties. The quake was located 18 kilometers or 11 miles west of the small town of Sarabetsu.

The U.S. Geological Survey (USGS) said that the epicenter of last week's quake was centered about 62 miles east-northeast of Miyako, off the coast of Sanriku. The rattling began at 4:53 p.m. local time. In addition to the initial earthquake, there was a secondary 5.6 magnitude aftershock less than an hour after the instigating event.