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Wednesday, May 1, 2013
Mt Fuji watch - signs of unrest continue as earthquakes possibly signaling magma movement occurring ! Landslides and ground fissures again could signal seismic activity as Mt Fuji..... something to keep an eye on !
On 3/3/2013, Fukushima Diary reported about the strong connection between the potential eruption of Hakone and Mt. Fuji.
(cf, Potential eruption of Hakone would trigger the eruption of Mt. Fuji [URL])
In this report, Fukushima Diary mentioned a professor emeritus Kimura from Ryukyu university. He commented,
Low‐frequency earthquake occurs just before an eruption or after. It’s caused by the movement of magma.
Low-frequency earthquake can suggest the potential volcanic activity.
According to National Research Institute for Earth Science and Disaster Prevention, the low-frequency earthquakes are rapidly increasing this April. The quakes are concentrated on the North East side of Mt. Fuji.
Most of the low-frequency earthquakes are 10~20km deep. The reason is not announced yet.
↓ Low-frequency earthquakes are increasing this April
Japanese scientists predict Mt. Fuji will blow due to new tectonic pressures that are higher than when the volcano last erupted more than 300 years ago. Estimates say the eruption will affect more than 400,000 people and cost over $30 billion.
The National Research Institute for Earth Science and Disaster Prevention has issued a warning that Japan’s 9.0 magnitude undersea quake last year, plus an aftershock four days later near Mt. Fuji, has created large pressure on the volcano’s magma chamber, which could lead to an eruption.
Mt. Fuji has already been classified as an active volcano, but scientists revealed new readings that show that the current pressure is at 1.6 megapascals, nearly 16 times higher than that required to trigger an eruption (0.1 megapascals).
It is "not a small figure", Kyodo News quotes lead volcanologist on the case as saying.
However, no signs of an eruption have so far been detected.
Nevertheless, “it’s possible for Mt. Fuji to erupt even several years after the 2011 earthquake, therefore we need to be careful about the development,” a team researcher stated.
Japan’s tallest mountain and national symbol poses a high risk to its own population.
In 2004, the government estimated a Fuji eruption would affect more than 400,000 people around the Tokyo area and cost $31.25 billion in damages. Further, volcanic dust from Mt. Fuji is said be likely to travel more than 100 km and be able to reach Tokyo, which could lead to the national capital losing its ability to function for several months, Wired Magazine reports.
Prefectures that could potentially be affected, such as Kanagawa, Yamanashi and Shizuoka (all in between Mt. Fuji and Tokyo), are planning to test run an evacuation by 2014 and local governments will prepare shelter plans by April 2013.
Newly-detected pressure is not the only thing that could trigger an eruption. Researchers published evidence in May that Mt. Fuji might even collapse if a newly-discovered fault-line underneath it were to shift. This could be triggered by various factors, including slight tremors in the surrounding area.
Fuji’s last recorded eruption was in 1707, which lasted for just over two weeks and formed a new crater and a second peak halfway down the side of the mountain. Fuji emitted 800 million cubic meters of volcanic ash, which spread over vast areas, even reaching the ancient capital of Edo, almost 100 km away.
Many people lost their lives from starvation after the eruption since they could not obtain food from their lands or move elsewhere because of damages caused by the volcano, stated Naomichi Miyaji from Nihon University.
Since the Great Tohoku Earthquake of March 2011, scientists have been anxiously watching the massive volcano known as Mt Fuji for signs of activity. In September of last year, a report was released stating that Mt Fuji’s magma chamber pressure had risen to a worrisome 1.6 megapascals, which is estimated to be higher than when it last erupted.
According to retired professor Masaki Kimura of Ryukyu University, this and other recent phenomena indicate an eruption of Mt Fuji should have taken place in 2011 with a four-year margin of error ending in 2015.
First, a little background on Mt Fuji. Japan sits on the edge of a “subduction zone” which is where one layer of the Earth’s crust is pushed under another. This pushing is an ongoing process and results in part of the Earth’s crust being pushed down into the hot magma of the Earth’s mantle. However, because this crust is saturated with water, it mixes differently with the magma in the mantle causing a lighter material to rise back up through the top layer of crust.
This rising magma then becomes a magma chamber. Here, away from the mantle, various gases are released from the magma and accumulate. When pressure becomes stronger than the rock containing it, the rock pops open in a volcanic eruption.
Mt Fuji was formed in this manner, and the subduction which occurs during large-scale earthquakes is believed to cause an increase in the magma chamber. The previous 1707 eruption of Mt Fuji is said to have been triggered by a massive earthquake occurring near Osaka a month before.
Prof Kimura believes that aside from the Tohoku earthquake there has been an overall increase in more “normal” seismic activity around the mountain – particularly on its northeast side.
“Magma is rising from beneath Mt Fuji. Cracks in the crust have been growing. Some things hanging above have been falling. No one is pointing it out, but I think there is a possibility.”
By “things hanging”, Prof Kimura is possibly alluding to the partial collapse of the Sasago expressway tunnel in December last year, which killed nine. Authorities are still investigating the cause of the collapse and no earthquake was detected at the time, but deformation of the tunnel is speculated as being the cause.
Prof Kimura also mentions the rise of the water level at Lake Sai which is located to the northeast of Mt Fuji. At the time of the Tohoku earthquake, the lake’s water-level rose by one meter. Kimura believes that this was caused by the permafrost near Fuji’s summit melted by rising magma.
Prof Kimura also claims that there have been a large number of phreatic eruptions – explosions of steam caused by heating of ground water from rising magma – around the mountain. No lava is released during these explosions, only water and rock.
However, some say that phreatic eruptions are precursors to major volcanic eruptions. Prior to the 1980 eruption of Mt Saint Helens in the US, there were numerous reports of phreatic eruptions. This is a theory which Prof. Kimura seems to agree with.
“It looks like the danger of eruption is in the northeast corner of Mt Fuji, but there is also a possibility of an eruption from the summit crater at the same time. Volcanic earthquakes are increasing, and their epicenters are becoming increasingly shallow.”
It should be noted that Prof Kimura is co-author of “Fujisan No Funka Wa Hajimatteiru!” (The Eruption of Mt Fuji Has Begun!), a book released in June last year, as well as author of 2011’s “Fujisan Dai Funka! Bukimina Itsutsu No Choko” (Mt Fuji’s Big Eruption! Five Eerie Signs).
Also, despite the evidence at hand it is still difficult to predict disasters like earthquakes and volcanic eruptions with absolute accuracy.
However, in the event of a Mt Fuji eruption, many speculate the cost to human life would be low due to the slow moving lava that would likely occur. On the other hand, the cost of damage to public and private property would undoubtedly be immense.
So if you’re planning purchasing any property in the vicinity of Mt Fuji, you might want to sit on it for a while.