Tag Archives: Natural Disasters and Hazards

The Japanese Sendai Nuclear Plant Threatened by the Sakurajima Volcano


Myself

By T.V. Antony Raj

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The lithosphere is the rigid, outermost shell on Earth. It comprises the crust and the part of the upper mantle that has an elastic behavior on, timescales of thousands of years or greater.

The scientific theory of plate tectonics describes the large-scale motion of Earth’s lithosphere. The geoscientific community accepted the theoretical model of plate tectonics developed during the first few decades of the 20th century based on the concept of continental drift. The concepts of seafloor spreading developed in the late 1950s and early 1960s.

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The tectonic plates of the world were mapped in the second half of the 20th century.
The tectonic plates of the world were mapped in the second half of the 20th century.

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The Earth’s lithosphere, the rigid outermost crust and upper mantle, is broken up into seven or eight major tectonic plates and many minor plates.

These massive slabs of the earth’s crust forever creep, slip, lock up and then jolt again. The typical annual lateral relative movement of the plates varies from zero to 100 mm.

Almost all creation of mountains, earthquakes, volcanic activity, and the formation of oceanic trenches occurs along these tectonic plate boundaries.

The islands that compose the Japanese nation sit on or near the boundary of four tectonic plates: the Pacific, North American, Eurasian and Filipino plates.

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The Pacific Ring of Fire
The Pacific Ring of Fire

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Also, Japan lies on the “Ring of Fire” also known as the circum-Pacific belt.  –  The Ring of Fire is a horseshoe-shaped band of fault lines in the basin of the Pacific Ocean, associated with a continuous series of oceanic trenches, volcanic arcs, and volcanic belts and  tectonic plate movements.  It has 452 volcanoes and has over 75% of the world’s active and dormant volcanoes. A large number of earthquakes and volcanic eruptions occur in this region.

Sendai Nuclear Power Plant

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The Sendai Nuclear Power Plant (Source: power-eng.com)
The Sendai Nuclear Power Plant (Source: power-eng.com)

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The Sendai Nuclear Power Plant, owned and operated by the Kyūshū Electric Power Company, is in the city of Satsumasendai in the Kagoshima Prefecture.  It is located near five giant calderas, a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, with the closest one about 40 km away from the plant.

Before the earthquake and tsunami of March 2011, and the nuclear disasters that resulted from it, Japan had generated 30% of its electrical power from nuclear reactors. It had planned to increase electrical power production to 40%.

Nuclear energy was a national strategic priority in Japan, but there had been concern about the ability of Japan’s nuclear plants to withstand seismic activity.

The earthquake and tsunami of on March 11, 2011, caused the failure of the cooling systems at the Fukushima I Nuclear Power Plant.  Japan then declared its first-ever nuclear emergency. This caused the evacuation of around 140,000 residents within 12 miles (20 km) of the plant.

On May 6, 2011, Prime Minister Naoto Kan ordered the shutdown of the Hamaoka Nuclear Power Plant as an earthquake of magnitude 8.0 or higher is likely to hit the area within the next 30 years.

Also, many other nuclear power plants, including the Sendai plant stopped  generating electricity.

In the wake of the Fukushima Daiichi nuclear disaster in 2011, Japan set new safety standards for its nuclear reactor plants.

On September 10, 2014, the Japanese Nuclear Regulation Authority (NRA) declared the Sendai Nuclear Power Plant safe for operation.

On August 11, 2015, Kyushu Electric Power Co., restarted its operation by bringing online the No. 1 reactor at its Sendai power station according to the new safety standards. Now it is providing power to the nearby towns again. Sendai is the first of Japan’s nuclear power plants to be restarted.

The Sakurajima Volcano

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View of Sakurajima from mainland Kagoshima in 2009
View of Sakurajima from mainland Kagoshima in 2009

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Sakurajima is an active composite volcano (stratovolcano) 990 km southwest of Tokyo. It is a former island in Kagoshima Prefecture in Kyushu, Japan. It is one of Japan’s most active volcanoes and erupts all the time. The lava flows of the 1914 eruption caused the former island to be connected to the Osumi Peninsula. The volcanic activity still continues, dropping large amounts of volcanic ash on the surroundings. Earlier eruptions built the white sands highlands in the region.

The Japan Meteorological Agency  on its website said that it believes that a larger than the usual eruption could be in the offing since it detected multiple earthquakes in the area on Saturday morning.  So, on Saturday, August 15, 2015, the agency raised the warning level for the volcanic island of Sakurajima from Level 3 to an unprecedented Level 4 (red). It has warned the residents in the villages on Sakurajima and has advised them to evacuate since stones could rain down on areas near the mountain’s base.

The Kagoshima prefectural government has formed an emergency response team.

The Kyushu Electric Power Company says a possible eruption on Mount Sakurajima will not affect the operation of its Sendai Nuclear Power Plant. The company made the comment after raising the alert level to 4. They said that they will collect the relevant data while proceeding with work to increase output as planned.

The Japanese Nuclear Regulation Authority (NRA) also says any possible eruption of the Sakurajima volcano will not affect the Sendai Nuclear Power Plant.

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Did Chang Hêng’s Seismoscope (“Earthquake Weathercock”) Ever Exist?


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Myself By T.V. Antony Raj .

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Earthquake

For more than eighteen centuries, people have used devices such as seismoscopes (“Earthquake Weathercock”) to study of earthquakes. The earliest known seismoscope recorded both the occurrence of earthquakes and the azimuth of their origins from the observer.

In the eighteenth century, there were schemes to record the times of earthquakes as well as the dynamics of the ground movement occurring in earthquakes. Significant progress resulted in the late nineteenth century with the development of instruments known as seismographs that produced records of ground motion in earthquakes as a continuous function of time.

The Chinese philosopher Chang Hêng, also called Choko and Tyoko, invented the earliest known seismoscope in 132 A.D. Needham says it resembled a wine jar of diameter six feet. There were eight dragon-heads on the outside surface of the vessel facing the eight principal directions of the compass. Below each dragon-head was a toad, with its mouth opened toward the dragon-head. The mouth of each dragon held an orb. Whenever an earthquake occurred one of the eight dragon-mouths would release an orb into the gaping mouth of the toad below it. The direction of the ground motion determined which of the dragons discharged its orb. Reports say the device detected an earthquake that occurred at a distance of four hundred miles from the site of the seismoscope.

However, to date, nobody knows about the inside of the Chang Hêng’s seismoscope. Seismologists of the nineteenth and twentieth centuries speculated on the mechanism of the Chinese seismoscope. Most believe it must have contained a device similar to a pendulum as the main sensing component to trigger one of the dragons to spew out an orb. In 1886, John Milne, a British geologist and mining engineer who labored on a horizontal seismograph, suggested that the pendulum was a suspended mass – a common pendulum.

In 1939, Akitsune Imamura, a Japanese seismologist, figured that the Chinese seismoscope might have housed an inverted pendulum. Takahiro Hagiwara, Professor Emeritus of the University of Tokyo, constructed an inverted-pendulum seismoscope which worked pretty much like Chang Hêng’s. As per reports the Chinese seismoscope indicated the azimuth of the earthquake. However, Hagiwara’s device responded to transverse movement. It indicated a direction normal to the azimuth between the observer and the epicenter.

In 1959, Needham suggested that Chang Hêng would have calibrated his device empirically for its direction-determining capabilities. He states that knowledge of Chang Hêng’s device existed for more than four hundred years. Works enumerating the functioning of “earthquake weathercocks” appeared as late as the end of the sixth century. Later, however, the seismoscope disappeared from Chinese’s disciplines.

Currently several Chinese writers have questioned whether Chang Hêng’s seismoscope ever existed.

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