Many experts are keeping their eyes on seismic activity occurring throughout Japan. That’s because recently a team of Japanese scientists have found that a number of active faults lie underneath a nuclear plant in northern Japan.
At the start of the new year, which began on Tuesday, Japan has been hit with 12 earthquakes with a magnitude of 4.1 and up, with the largest being a 4.9 trembler hitting the region a few hours ago.
If you compare last year’s quakes over the same three day period, Japan was only subject to 5 quakes, though one of them was a magnitude 7.0.
The region known as the “Ring of Fire” has seen an uptick in seismic movement since the end of November 2012, with numerous earthquake swarms reported in the region in the last sixty days.
Following last year’s terrible magnitude 7-class Japanese quake the Nuclear Regulation Authority commissioned a four-member panel to investigate the threat earthquake activity might pose to Japans infrastructure of nuclear plants.
The panel’s most recent finding states that the faults they investigated could cause magnitude 7-class earthquakes near the reactor in question, which was opened in 2005 and is among the newest of Japan’s aging reactors.
Their findings were diametrically opposite of claims made by operators of the plant who had reported the faults as being inactive.
Modern day nuclear plants are designed to withstand earthquakes and, in the event of major earth movement, they are programmed to safely shut down.
After the magnitude 7.2 Kobe earthquake in 1995 the safety of nuclear facilities in Japan was reviewed along with the design guidelines for their construction. The Japanese Nuclear Safety Commission prescribed and approved a series of new standards.
After recalculating the seismic design criteria required for a nuclear power plant to survive near the epicenter of a large earthquake, the NSC concluded that under current guidelines, such a plant could survive a quake of magnitude 7.75. The Kobe earthquake was 7.2.
The magnitude 9.0 Tohoku-Taiheiyou-Oki earthquake which hit at 2.46 pm on March 11, 2011 did considerable damage, and the tsunami it created, with run-up height of 40 meters, caused even more greater damage. Most experts in the field of seismology believe it was a double quake that led to the severe duration of approximately three minutes in length.
Its enormous power moved Honshu four meters east and apparently subsided the nearby coastline by half a meter.
Eleven reactors at four nuclear power plants in the region were operating at the time and all shut down automatically when the quake hit. Power was available to run the cooling pumps at most of the units, and they achieved cold shutdown in a few days. However, at Tepco’s Fukushima Daiichi plant, a major accident sequence commenced. The three reactors were shut down by the earthquake and the emergency diesel generators started as expected, but then they shut down an hour later when submerged by the tsunami, about 15 meters high at that point. Other systems proved inadequate and led the authorities to order, and subsequently extend, an evacuation while engineers worked to restore power and cooling.
In the event’s aftermath, it’s quite clear that though Japan may have been prepared to withstand such a powerful quake, the tsunami exposed the region to unforeseen destruction and dangers.
Initially, Japan’s Nuclear & Industrial Safety Agency declared the Fukushima accident as Level 5, the same level as Three Mile Island in 1979, but after new estimates of radioactive releases in the first few days of the accident, the disaster was reclassified as a level 7.
There is reason, to this day, to believe that the real after-affects of the quake are still to be known.
Considering the swarm of quakes that are now outnumbering the 2012 record,it is perhaps wise for all of us to keep an eye on seismic activities worldwide, but especially on Japan.
D. Chandler contributed to this report