Comments
The day after an undersea earthquake of magnitude 7.4 (M7.4) on the Richter Scale struck off the East Coast of Japan, a number of aftershocks of M5 or lower have been recorded across Honshu, the main island.
The latest aftershock of M5.3 was reported at 2.06 pm local time off the North-West coast of Ishigakijima Island at a depth of 180 km, the Japanese Meteorological Agency said at the time of going to press. The M7.4 earthquake had occurred at a much shallower (and therefore with comparably higher damage potential) depth of 60 km.
Watchout for next few days
The Meteorological Agency on Thursday urged the public to watch out for more seismic activity in the next few days. It advised people in affected areas to stay away from the coast and not to enter the sea until tsunami advisories are lifted. It also warned them against the risk of mudslides.
The US Geological Survey (USGS) said Wednesday’s event was triggered as the result of ‘thrust-faulting’ at or near the subduction zone plate boundary interface between the Pacific and North America plates.
At the location of this earthquake, the Pacific plate moves approximately westward relative to the North America plate at a velocity of roughly 70 mm/year, subducting beneath Japan at the Japan Trench and dipping to the West beneath Japan.
Preceded by a M6.4 event
The USGS said the M7.4 event was preceded by a M6.4 foreshock approximately two minutes earlier. In February last year, an M7.1 earthquake had occurred about 15 km east of the epicentre of the current events. Wednesday’s events had occurred in the vicinity of the rupture area of the Great M9.1 Tohoku earthquake of March 11, 2011.
An aerial view shows damage to northern Honshu after a 9.0 magnitude earthquake and subsequent tsunami devastated the area in March 2011
The March 2011 earthquake was widely felt on the islands of Honshu and Hokkaido of Japan. It had also generated a giant tsunami wave that caused extensive destruction along the Japanese coast and propagated throughout the Pacific Ocean basin. It was at least 63 times stronger than Wednesday’s event and released about 500 times more energy.
Great M9.1 Tohoku event
Approximately 22,000 people perished as a result of the earthquake and subsequent tsunami. The epicentre of Wednesday’s earthquake was located about 100 km from that of March 2011 earthquake.
The USGS said that in the past century, 33 earthquakes of M7 or greater have occurred within 250 km of this event, including seven of magnitude greater than 7 (>M7) since the March 2011 M9.1 event.
Last year’s quake events
Earlier last year, three major earthquakes had struck offshore Sendai and Fukushima. The first two, both M7.1 events, had occurred on February 13 and March 20, 2021. A third one of M6.9 struck occurred on May 1.
The three quakes struck within 100 km of each other and were strong enough to rattle major population centres of the northern part of Honshu. These were just a few of the thousands of temblors that struck the quake-prone region in the last decade since the March 2011 M9.1 Tohoku earthquake.
Comments
COMMENT NOW
Comments
Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide by our community guidelines for posting your comments.
We have migrated to a new commenting platform. If you are already a registered user of TheHindu Businessline and logged in, you may continue to engage with our articles. If you do not have an account please register and login to post comments. Users can access their older comments by logging into their accounts on Vuukle.