Japan's Devastating Aftershock

Apparently, one quake is not enough. An aftershock as powerful as 7.1 attacked North-eastern Japan at 11:32 PM on Thursday, April 7. This aftershock quake caused strong tremors in areas already devastated by the March 11th earthquake and tsunami. And of course, this quake unsettled many people who had taken refuge at makeshift shelters since being displaced by last month's disaster


Several buildings were destroyed and power was cut to 3.6 million homes. This aftershock killed four people and left 141 others injured, police and hospital officials said Friday.

The quake at 40 kilometers below ground, but later, it was revised to 66 kilometers deep.

Also, earlier reports stated that it had a magnitude of 7.4 but that was later revised to 7.1, according to the US Geological Survey (USGS).

The quake raised a tsunami warning, but thankfully, no tsunami attacked Japan this time and the warning was lifted after 90 minutes.


The 11:32 p.m. quake, registering a revised magnitude of 7.1, was the first to measure in the upper 6 level on the Japanese seismic intensity scale of 7 since the March 11 magnitude 9.0 earthquake and tsunami that struck northeastern and eastern Japan.

Moreover, nuclear power plants and related facilities in the coastal areas of northeastern Japan were forced to rely on emergency power after their electricity was cut off in Thursday night's quake.

Operations have been suspended at all nuclear power plants from Aomori to Ibaraki prefectures since the March 11th earthquake and tsunami. But electricity is still crucial to keep their cooling systems operating.

Japan's nuclear agency says all external power lines at Higashidori nuclear power plant in Aomori Prefecture were knocked out in Thursday's quake. The plant switched to emergency diesel power generators for some hours, but power was later restored.

The quake shut down 3 of the 4 external power lines at Onagawa nuclear power plant in Miyagi Prefecture. It is still operating on the one remaining power line.

The Onagawa plant also suffered water leaks at 8 locations, including water that spilled from spent fuel storage pools at each of its 3 reactors. A device to control pressure inside a turbine building was also damaged.

As if it's not enough, the power outage caused by this quake knocks out seismic data transmitters. The meteorological agency said that as of 10 AM Friday, it had confirmed lack of data transmission from 14 seismometers in locations including Ishinomaki City in Miyagi Prefecture and Tanohata Village in Iwate Prefecture. Another 4 seismometers had already been out of order since the March 11th quake and tsunami. The total of 18 malfunctioning seismometers accounts for 20 percent of all seismometers set up in northeastern Japan.

The agency also said data transmissions from 12 of 26 seismometers used for measuring quake magnitudes and issuing quake warnings have also stopped. Osamu Kamigaichi, Senior Agency Official, stated that the lack of seismic data poses no problem for issuing tsunami warnings, but will affect the accuracy of quake warnings.

China has urged Japan to observe international law and adopt effective measures to protect the marine environment, amid concern over the discharge of contaminated water into the Pacific Ocean. The foreign ministry also asked Japan for swift, comprehensive and accurate reports on the crisis. Fish exports from Japan have been hit by the radiation leaks.

Source:
Kyodo News
NHK
BBC