The fault that caused Monday's 6.8-magnitude earthquake off the Chuetsu region of Niigata Prefecture runs directly below Kashiwazaki-Kariwa Nuclear Power Plant, experts have found.
     Small radioactive leaks and dozens of malfunctions have been reported at the plant since the quake, which registered upper 6 on the seismic intensity scale of 7 in Kashiwazaki in the prefecture.
     The revelation is likely to affect the operator's decision on when to resume operations as well as whether to review the quake-resistance strength of the facilities.
     Experts analyzed the distribution of aftershocks and found that an undersea fault where the earthquake struck extends inland right beneath the nuclear power plant. The plant was built under the assumption that the maximum temblor to hit the area would be around 6.5 in magnitude.
     The focus of Monday's quake was 17 kilometers deep and 9 km north of the plant.
     Experts of the Japan Meteorological Agency, the National Research Institute for Earth Science and Disaster Prevention and the University of Tokyo's Earthquake Research Institute separately studied the aftershocks.
     They found that their focuses were centered mainly southwest of the main temblor's and in an area straddling both the sea and land along the coast.
Monday afternoon's 5.8-magnitude aftershock, which registered an intensity of lower 6 in some areas, is believed to have been focused inland.
     Because aftershocks occur at parts of the fault that slipped as a result of the main temblor, the distribution of aftershocks shows where the fault plane lies.
     The fault plane in Niigata is believed to extend from beneath the Sea of Japan, slanting downward in an inland direction, according to the experts.
     The portion of the fault plane in the land area right below the nuclear plant is more than 20 km deep. The portion away from the plant is shallower.
     The shallower portion is believed to have caused bigger jolts.
     "Just because the fault is right below (the nuclear plant) does not mean that it is risky," Kazushige Obara, who is in charge of seismic data at the National Research Institute for Earth Science and Disaster Prevention, said.
     Still, the power plant, which has seven reactors, was built on the assumption that no active fault lies beneath the location.
     Quake-resistance calculations were based on a maximum quake smaller than Monday's temblor.
     "When the plant's application for construction was submitted, such a temblor (as Monday's earthquake) was likely beyond the scope of calculations," said Masaaki Tateishi, professor of geology and sedimentology at Niigata University. "There is a pressing need to re-evaluate the quake-resistance strength (of nuclear power plants)."
     Representatives of Tokyo Electric Power said that the company was aware of such issues, and that it may conduct its own study if more data on Monday's temblor is released.

     The structural safety of nuclear power plants in earthquakes has emerged as a critical issue following Monday's powerful temblor in and around the Chuetsu region of Niigata Prefecture. At the Kashiwazaki-Kariwa Nuclear Power Plant run by Tokyo Electric Power Co. near the epicenter, the tremor was well beyond the level of intensity for which this plant has been designed. Radioactive water spilled from a building housing a nuclear reactor and flowed into the Sea of Japan. A transformer on the plant premises caught fire.
     The shaking from Monday's quake was the strongest ever recorded at a nuclear power plant in Japan. Although the epicenter was only about 9 kilometers away, there is no excuse for the fire and the spillage of radioactive water. As a basic premise, each nuclear power plant should be built with every safety measure against contingencies.
     As many as 55 nuclear reactors dot this earthquake-prone archipelago. The 2005 earthquake off the coast of Miyagi Prefecture and the Noto Peninsula earthquake in March were both stronger than anticipated at the Onagawa Nuclear Power Plant of Tohoku Electric Power Co. and the Shika Nuclear Power Plant of Hokuriku Electric Power Co., respectively.
     All nuclear power plants around the nation must recheck their structures for earthquake safety, and take necessary measures at once.
     Monday's quake is believed to have been caused by an active fault in the seabed that had not been considered dangerous. It is possible that Japan is sitting on any number of yet-to-be-known active faults. A much more thorough survey of active faults is called for, and we believe this is one important lesson taught by the latest quake.
     Earthquake-proof guidelines were reinforced last year for the first time in about 30 years. Experiences from the Great Hanshin Earthquake of 1995 and other temblors made it clear that the old guidelines were inadequate because they were calculated only on the basis of a near-field earthquake with a magnitude of around 6.5.
     While the new guidelines do not give any specific number for the intensity of the anticipated earthquake, they are said to imply a jolt with a magnitude of around 6.8.
     But Monday's quake was of magnitude 6.8, and it caused the radioactive water to spill and a fire. We need to re-examine the adequacy of the new guidelines.
     The Kashiwazaki-Kariwa plant proved ill-prepared for the quake, and its handling of the situation was anything but commendable. The operators of the plant should have foreseen that an earthquake would shake the storage pool for spent fuel and cause its radioactive water to spill. But instead of ensuring that the spill was contained in a managed area, the operators let the water leak out of the premises.
     They must find out exactly where and how they erred. Other nuclear power plants likely have similar defects.
     Although the transformer that caught fire was far from any of the nuclear reactors on the premises, it was a dangerous incident all the same. We suspect the operators lacked precautions for a possible overload in an earthquake. It is believed that the transformer's insulator oil caught fire, but we wonder why this occurred so easily.
     A bigger question is why it took nearly two hours to extinguish the fire. Apparently, local firefighters were late in arriving, but it makes us uneasy to think that the plant workers were unable to douse the fire swiftly by themselves.
     The Kashiwazaki-Kariwa plant is relatively new. But what if the same thing had happened at an old plant? The damage must be investigated thoroughly, and lessons must be learned.

     TOKAIMURA--About 480 liters of hydrochloric acid leaked from an outdoor tank for a nuclear safety research reactor at the Japan Atomic Energy Agency's Nuclear Science Research Institute here, agency officials told the fire department Wednesday morning.
     No one was injured and there were no radioactive leaks from the reactor, officials said. Hydrochloric acid is used to purify the water used to operate the reactor.
     About 920 liters were originally in the tank. The leaked acid was collected in a tray beneath the tank and then pooled in another tank, where it is to be neutralized and disposed of.(IHT/Asahi: July 19,2007)
     Why is Niigata prone to quakes? / Scientists analyze links between latest incident and 2004 Chuetsu temblor
The Yomiuri Shimbun (Jul. 18, 2007)

     A crack caused by the Niigata Prefecture Chuetsu Offshore Earthquake is seen along a section of the Hokuriku Expressway, near the Nishiyama interchange in Kashiwazaki, Niigata Prefecture, on Monday.
     Less than three years since the October 2004 Niigata Prefecture Chuetsu Earthquake that killed 67 people, another strong quake of upper 6 intensity on the Japanese seismic scale jolted the prefecture Monday.
     Experts put the reason for the series of major quakes in the prefecture down to the existence of a tectonic belt where seismic strains are concentrated.
     According to an analysis by the Meteorological Agency, the latest earthquake was caused by a fault slip at a very shallow part of a plate. The depth of the quake's focus was about 17 kilometers below the seabed with a magnitude of 6.8.
     Its magnitude was almost identical to the 2004 Chuetsu Earthquake, but the focus this time was about 40 kilometers northwest of that of the 2004 earthquake, so a different fault from the previous quake is believed to have moved. The focus of the latest quake was offshore and the existence of the fault was previously unknown.
     In Iizunamachi, Nagano Prefecture, about 80 kilometers from the focus, an intensity of upper 6 was recorded. The agency's Earthquake and Tsunami Observation Division said the area's soft ground intensified the jolt.
     Quakes that occur at shallow depths are called epicentral or inland quakes. The Great Hanshin Earthquake in January 1995 and the Noto Peninsula Earthquake in March both fall into this category. This type can occur anytime anywhere across the country.

     Across the Japanese archipelago, the Pacific plate and the Philippine Sea plate subduct under the land plates and strain energy accumulates through the power of the land plate pushing back the power of the sea plates. When the strain reaches its limit, the power is freed, faults in weak ground are exposed and a quake occurs.
     Why has Niigata Prefecture been hit by two strong quakes in a relatively short period of time?
     The Chuetsu Offshore Earthquake occurred in a belt named the Niigata-Kobe tectonic belt, much like other great inland quakes, such as the Great Hanshin Earthquake, the Nobi Earthquake and the Chuetsu Earthquake.
     The existence of the belt was revealed in 2001 for the first time from data of the Geographical Survey Institute's global positioning system. The strain is concentrated in a belt of about 50-200 kilometers between Niigata Prefecture and Kobe, with land and sea plates pushing each other about two centimeters annually. The rate is estimated at up to 10 times higher than surrounding areas.
Takeshi Sagiya, an associate professor at Nagoya University who analyzed the data, said: "The strong relationship between the concentration of strains and quakes with magnitudes of about 7 has been reinforced [by the latest earthquake]. Preparations for earthquakes are necessary because there are active faults which have not caused quakes."

Link to Chuetsu Earthquake
     Shinji Tooda, senior researcher at the National Institute of Advanced Industrial Science and Technology's Active Fault Research Center, said it was highly likely the Chuetsu Offshore Earthquake was induced by the Chuetsu Earthquake.
     According to Tooda, after a quake, areas appear with decreased strain caused by reduced pressure and those with increased strain caused by heightened pressure.
     Tooda calculated the changes in pressure to the crust around quake areas just after the Chuetsu Earthquake and applied the calculation to the focus of the Chuetsu Offshore Earthquake and discovered about one-fifth of the atmospheric pressure was added to places around the quake's focus.

Repeated aftershocks a concern
     Since it is highly possible the areas of the Chuetsu Offshore Earthquake have a very similar crust structure to that of the areas of the Chuetsu Earthquake, repeated aftershocks are a concern.
     Prof. Hiroshi Sato of Tokyo University's Earthquake Research Institute said: "The areas of the Chuetsu Offshore Earthquake have many factors consistent with those of the Chuetsu Earthquake. It's certain there are areas more vulnerable to aftershocks, such as places where old wounds exist from the time when the Japanese Archipelago was dragged away from the Asian continent to create the Sea of Japan."
     The elements of the Chuetsu Offshore Earthquake are the same as the Chuetsu Earthquake, but if the manner of the fault destruction was simpler, aftershocks would be reduced. So far, the agency said, aftershocks would be fewer than the Chuetsu Earthquake. But Kei Katsumata, associate professor at the center, said, "We can't drop our guard because there is a pattern in which aftershocks increase, even if there are not many just after the main quake."

The municipal government of Kashiwazaki, Niigata Prefecture, issued an emergency order Wednesday to Tokyo Electric Power Co. to shut down a nuclear power plant where a radiation leak and transformer fire occurred after Monday's Niigata Prefecture Chuetsu Offshore Earthquake.
It also has been revealed through aftershock analysis by a group of experts from institutes including the National Research Institute for Earth Science and Disaster Prevention, based in Tsukuba, Ibaraki Prefecture, that it is likely the fault that caused the earthquake stretches directly under the Kashiwazaki-Kariwa nuclear power plant.
All of the plant's seven reactors have been suspended under the order based on the Fire Service Law. This is the first time TEPCO has been ordered to shut down a facility under the law. The order was issued as the safety of equipment, such as outside storage tanks used with power generating turbines, cannot be assured. As the plant cannot be operated until the equipment is confirmed to be safe, the order is tantamount to suspending the operation of the plant.
The decision was made based on investigations by the city government and the Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency.
Kashiwazaki Mayor Hiroshi Aida summoned TEPCO's President Tsunehisa Katsumata to the city hall at 11 a.m. and issued the order. Kashiwazaki and Kariwamura municipal governments also told TEPCO on Wednesday that, based on safety agreements with the power company, the plant must only be reopened after TEPCO gains permission from local municipalities. Katsumata apologized to the mayor.

     Analysis by the group of seismic waves and aftershock distribution has shown it is likely the fault that set off the earthquake stretches directly under the plant.
The magnitude 6.8 temblor's focus was about nine kilometers north of the plant and about 17 kilometers below the seabed. Aftershocks have been distributed in a southwesterly direction from this seismic source.

     KASHIWAZAKI, Japan (AP) -- The world's largest nuclear power plant was ordered closed indefinitely amid growing anger over revelations that damage was much worse than initially announced after it suffered a near-direct hit by a powerful earthquake earlier this week.
     Toyota and other major automakers meanwhile announced they would temporarily halt production because a local parts maker was heavily affected by the magnitude-6.8 quake, which killed 10 and left tens of thousands in the region without power or water.
     The mayor of Kashiwazaki, a city of 93,500 on Japan's northern coastline, called in the head of the nation's biggest power company on Wednesday and ordered the damaged facility closed until its safety could be confirmed, escalating a showdown over a long list of problems at the plant, which is the world's biggest in output capacity.
     "I am worried," Mayor Hiroshi Aida said in issuing the closure order. "The safety of the plant must be assured before it is reopened."
     Repercussions were felt in the business world and overseas as well.
     The temporary closure of auto parts maker Riken Corp.'s plant at Kashiwazaki forced Toyota Motor Corp., Nissan Motor Co., Mitsubishi Motors Corp. and Fuji Heavy Industries to scale back production.
     Toyota, Japan's No. 1 automaker, will stop production lines at a dozen factories centered in central Aichi prefecture Thursday afternoon and all day Friday, said Toyota spokesman Paul Nolasco.
     The International Atomic Energy Agency pressed Japan to undertake a thorough investigation of the damage to see if lessons could be applied to nuclear plants elsewhere.
     Speaking in Malaysia, IAEA chief Mohamed ElBaradei said such a review was key and offered help from his Vienna-based agency.
     "I would hope and I trust that Japan would be fully transparent in its investigation of that accident," he said.
     Officials at Tokyo Electric Power Co., the company running the plant, said the damage caused by the quake posed no danger to residents or to the environment.
But there was visible damage on the site, from cracked roads and buckled sidewalks to the charred outside wall of a transformer building.
     TEPCO also warned Wednesday that the closure of the key nuclear reactor could trigger a power shortage in the summer months. The Tokyo-based company has asked six other power companies in Japan to consider providing emergency electricity to prepare for a surge in demand as people turn up their air conditioners in the summer heat, according to TEPCO spokesman Hiroshi Itagaki.
     "To be honest, it's a mess," said TEPCO President Tsunehisa Katsumata.
But he said fears of radiation leaks were unfounded.
     "We will conduct an investigation from the ground up. But I think fundamentally we have confirmed that our safety measures worked," he said. "It is hard to make everything go perfectly."
     Though Japan is one of the world's most earthquake-prone countries, officials at the plant admitted that they had not foreseen such a powerful temblor hitting the facility.
     New data from aftershocks of Monday's offshore quake suggested a fault line may run underneath the power plant itself, which was only 19 kilometers (12 miles) from the epicenter.

     Quake damage at the Kashiwazaki-Kariwa Nuclear Power Plant was more extensive than initially thought, with radioactive materials discharged into the air, barrels of waste overturning and transformers leaking oil, officials said.
Tokyo Electric Power Co. (TEPCO), operator of the plant in Niigata Prefecture, said 50 cases of mechanical glitches and damage were confirmed at the plant's seven reactors after Monday's powerful quake rocked Niigata and Nagano prefectures.
     The latest findings came after TEPCO acknowledged that water containing radioactive materials flowed into the Sea of Japan because of the temblor and that an electric transformer caught fire.
     Although TEPCO says the radioactive substances that leaked outside pose no health risks, the damage exposed the vulnerability of nuclear power plants in major earthquakes, experts warn. The Kashiwazaki-Kariwa Nuclear Power Plant was designed to withstand shaking from a quake at a level much lower than what was recorded Monday.
     "We need to review (the situation), including conducting anti-quake reinforcement work," a TEPCO official said.
     Kashiwazaki Mayor Hiroshi Aida on Wednesday ordered TEPCO to suspend the use of hazardous facilities, such as fuel tanks, at all reactors in the plant "until safety is confirmed."
     The mayor's emergency order, in accordance with the fire prevention law, came after he summoned TEPCO President Tsunehisa Katsumata and Akio Takahashi, head of the plant.
     The suspension of nuclear reactors cannot be ordered based on the fire prevention law. But if operations of hazardous facilities are halted, it effectively means that the entire nuclear plant will have to shut down.
     The quake had a magnitude of 6.8 and an intensity of upper 6 on the Japanese scale of 7. The epicenter of the quake was an estimated 9 kilometers from the plant's location.
     The radioactive substances that leaked into the air came through the main exhaust stack used to decontaminate air inside a steam condenser.
     The condenser cools steam generated at the reactor and converts it back into water. The air is decontaminated and discharged through the exhaust stack.
     When TEPCO conducted checks Tuesday, it detected radioactive substances, such as iodine, chrome and cobalt, outside the reactor, the company said.
     The company said an estimated 300 million becquerels of radiation was detected at the plant, a figure about one-thousandth of the legal limit, TEPCO said, adding that there should be no ill effects on people or the environment.
But the company said it has yet to determine the cause of the leak at the No. 7 reactor exhaust stack. TEPCO said radioactive materials are usually kept inside nuclear reactors.
     The earthquake also caused exhaust ducts at the No. 1, 2, 3, 4 and 5 reactors to shift a little, but TEPCO officials said there was only a small likelihood that air containing radioactive substances had leaked outside the reactor.
     In addition, the shaking caused about 100 metal barrels containing low-level radioactive waste to topple. The lids of some of the barrels came off.
     Radioactive materials measuring 0.5 becquerels per square centimeter were confirmed from part of the floor.
     About 22,000 barrels, containing waste such as screws, piping materials, gloves and incinerated ash, are kept at the plant's two storage buildings.
     Meanwhile, the water containing trace amounts of radioactive materials from a spent fuel pool at the No. 6 reactor continued to leak inside the plant on Tuesday.
     The leak started Monday after the quake rocked the spent fuel pool, causing the water to flow into drainage ditches leading to the Sea of Japan.
     The flow of the radioactive water outside was stopped on Monday, but one drop of radioactive water formed every three seconds Tuesday inside the reactor building.
     The earthquake also caused other spent fuel pools to overflow, flooding the top floors of the reactor buildings.
     In addition, seven electric transformers other than the one that caught fire were found to have suffered minor damage, such as oil leaks and broken bolts.
     At least one water-supply pipe for fire-fighting was damaged, resulting in water  leaks, TEPCO said.
     "It cannot be denied that a fire might have occurred at several transformers, and the fire control equipment was not functioning properly," the TEPCO official said.
     On-site inspections of the plant by Kashiwazaki city's fire department Tuesday found parts of the ground damaged and pipes deformed. Department officials said hazardous facilities, including an outdoor oil storage area, may have also been damaged.(IHT/Asahi: July 19,2007)

     The nuclear power plant where a radiation leak and transformer fire occurred after the earthquake was told two years ago by the International Atomic Energy Agency that it lacked fire prevention measures, it was learned Wednesday.
     Even though Tokyo Electric Power Co. reviewed the measures after the IAEA's evaluation that was issued in 2005, the fact that it took two hours to extinguish the fire suggests efforts to improve circumstances were insufficient.
     The IAEA sent a team of experts to TEPCO's Kashiwazaki-Kariwa nuclear power plant in November 2004. The 16-member team examined the safety management system and interviewed the employees.
     A report of the examination released in June 2005 criticized the fire control measures, saying:
     * There was no section in charge of fire prevention measures.
     * Some members of the volunteer firefighters group at the power plant were not trained, and other members are not engaged in periodic safety patrols.
     * A fire control committee has not met for two years.
     The report urged TEPCO to strengthen the fire control system and improve the quality of fire drills.
     After the report, TEPCO held a joint fire drill with the local fire station and appointed an official in charge of fire prevention. The IAEA acknowledged that the problems were solved by the time it reexamined the power plant in May last year, the company said.