Geologist and anti-nuclear power campaigner Kazuro Kawamoto
talks to Simon Piggott
Q. Why do earthquakes occur?
A. Apart from its core, most
of the Earth is made up of soft rocks. And these rocks are hot. They
still retain heat from the birth of the Earth around 4600 million
years ago. However, from the Earth’s surface to a depth of about 100
kilometers the rocks have cooled down. This upper layer includes a
number of “plates”. The islands of Japan are located at a point
where two of the plates, the Pacific plate and the Philippine Sea
plate, come into contact with two continental plates, the Eurasian
plate and the North American plate. In fact, the Japanese islands
came into being as a result of this collision, which pushed up
sedimentary rocks from the seabed to form 3000 meter-high
These plates are still moving. For example, the Ogasawara islands
are located on the Philippine Sea plate, and we know that every year
they get 3.8 centimeters closer to Honshu. Where the Philippine Sea
plate has pushed under the Southwest Japan plate (which is part of
the Asian continent) the two plates are meshed tightly together.
Meanwhile, tension continues to build. When the strain becomes too
great sudden movement at the interface of the two plates occurs.
This is an earthquake, and the amount of energy released is
expressed numerically in the earthquake’s magnitude.
Do earthquakes happen at regular intervals?
In Japan they do. For example, a Tokai earthquake
resulting from plate movements under Suruga Bay and Shizuoka
will occur every 100 to 150 years. Nankai earthquakes, which
are centered off the coast of Shikoku, have a cycle of the same
sort. Actually the two are related. In 1707 and 1854 Tokai and
Nankai earthquakes occurred almost simultaneously.
Can we expect a large earthquake in the Tokai region in the
Yes. The last major Tokai quake was in 1854. The
one before that was in 1707. That’s an interval of 147 years. So the
next one is due.
How easy is it to predict exactly when an
earthquake will strike?
This is much more difficult. For
example, in the Tokai region a major quake is expected to be
directly preceded by sudden fluctuations in the level of Omaezaki
cape. The Japan Meteorological Agency has bored holes in this area
to detect any sudden rock deformations that occur at the very
beginning of the quake. In all probability there will be a few hours
warning. But there is no guarantee.
What power of quake and what sort of damage can be
The latest predictions, in 2001, were for a
magnitude-8. This is ten times greater than the earthquake in Kobe
According to the Japan Meteorological Agency, in many
places the seismic intensity will be at the top of its scale of 7
(equivalent to XII on the international Mercalli Scale).
A quake’s “intensity” indicates the actual movement of the
ground. According to JMA, an intensity-7 quake will destroy at least
30 per cent of all buildings. In Kobe only a very small area
experienced such an intensity, with catastrophic results. In the
Tokai earthquake it will be much larger. Wide areas of newer
sedimental strata between Mishima and Hamanako lake could receive
intensity-7 shocks. Projections are for 5,900 deaths and 19,000
injuries in Shizuoka Prefecture. However, these calculations were
made before the latest predictions, which suggest more deaths and
injuries in the western part of the prefecture.
What is the
scale of damage outside Shizuoka likely to be?
figures envisage 1010 deaths in Kanagawa, 344 in Yamanashi, 211 in
Gifu, 95 in Aichi and 71 in Nagano. I feel that the figure for Aichi
is rather conservative. The new predictions show the city of Nagoya
experiencing an intensity-6 shock, which will cause weak wooden
buildings to collapse.
However, the greatest worry is the safety
of the nuclear power plant at Hamaoka, which is located in a part of
Shizuoka with considerable seismic crustal deformation. Here the
land could rise 1-2 meters in little more than a minute. Hamaoka is
a large plant with four reactors (and an additional one under
construction). If any one of these reactors suffers a meltdown as a
result of damage incurred during the quake it may lead to thousands
of radiation-related deaths.
But surely the danger of a major
earthquake was taken into account in the planning and construction
of the plant?
The construction of the first two reactors,
which went into operation in 1976 and 1978, did not take into
consideration the high risk of their location. They were designed to
resist only a 450-gal acceleration level in the intensity of the
impact. It was not until 1976 that a detailed model for the coming
Tokai earthquake was made — with resultant and widespread public
concern. This was followed in 1978 by a law requiring the
implementation of an earthquake observation system. Consequently, a
new resistance level of 600 gal was established for reactors 3 and
4, as well as for reactor 5, now being constructed. However, in Kobe
in 1995 a level of 800 gal was recorded in some places. For Tokai,
the authorities’ estimation of the intensity derives from a
simplified model based on a premise that all of an earthquake’s
energy will emanate from the central point of the earthquake fault
plane. This point is set at a distance away from Hamaoka. But, here
there are two problems: first, there could be a considerable
underestimation of the impact on Hamaoka, which is located on a big
earthquake fault. And second, they haven’t taken into account the
possibility of the earthquake being much more complex in nature.
No nuclear reactor anywhere in the world has ever experienced
such as powerful earthquake as we expect to strike Hamaoka in the
near future. So the situation is extremely worrying.
the reactors shutdown automatically in an earthquake?
case of Hamaoka there is an automatic shutdown mechanism when the
shock exceeds a certain level. However, after shutdown it requires a
number of days for the reactor core to cool. If the earthquake
destroys the normal and emergency cooling systems, meltdown is
unavoidable. Reactors 1 and 2 are nearing their life expectancy of
30 years and have lately suffered several malfunctions. This makes
us even more anxious. In fact, operations at both reactors have been
suspended since November 2001 due to the hydrogen explosion of a
pipe connected to the emergency core cooling system of reactor 1. At
the moment a campaign is being conducted by a citizens’ groups to
prevent the two problematic reactors from being put back into
service and to halt the operation of reactors 3 and 4 until after
the expected earthquake has occurred. Legal proceedings are being
In the worst case, if an earthquake did cause one of
the Hamaoka reactors to explode what would happen?
large-scale steam explosion resulting from a meltdown, around 20 per
cent of the radioactive material in the reactor would be released
into the environment. It would be approximately the same amount as
that of the Chernobyl disaster in 1986. With average winds, the
radiation would take two hours to reach Shizuoka and Hamamatsu, five
hours to Nagoya and seven hours to Tokyo.
In such a situation
how should one react?
You must remember that serious damage
from the earthquake will have put out public transport and caused
enormous traffic jams. So it will probably be impossible to escape
from the radiation area. Anyway, first, check the direction and
speed of the wind (the prevalent wind direction at Hamaoka is
eastward towards Tokyo, but on one out of four days there will be a
west wind blowing towards Nagoya). On a fine day the radiation will
be spread over a wider area. On a cloudy day it will stay lower. If
it’s raining stay out of the rain!
Radioactive particles can be inhaled from the air. If you think
that you have been exposed, remove your clothing and wash your body.
Short-life, high-level radioactive isotopes cause acute radiation
disease. Also, remember that children are at high risk from
radioactive iodine, which causes thyroid cancer. Since the body
absorbs iodine from the atmosphere, as well as from drinks and food,
it would be useful to have an emergency supply to cover the crucial
first several weeks (the first tablet must be taken before
exposure). Radioactive iodine has a relatively short half-life of 8
days. This means that its power decreases by half every 8 days--down
to 50 per cent after the first 8 days, to 25 per cent after 16 days,
and so on. Local government offices within 8 kilometers of nuclear
plants have free supplies of iodine tablets to distribute to
citizens, but distribution will be almost impossible. No other towns
have any such contingency plans.
Over a wide area locally produced vegetables, meat, milk and
other fresh foods will be polluted, so avoid them. Water supplies
may also be affected.
It’s an apocalypse scenario. But, although the earthquake itself
is unavoidable, the authorities can certainly avoid the concomitant
Chernobyl-style disaster by taking the decision to suspend
operations at Hamaoka. As citizens and residents of this country,
each of us possesses the freedom and right to encourage them to do
Kazuro Kawamoto is curator of the award-winning Median
Tectonic Line Museum in Oshika, Nagano. The museum, which is open
Tues-Sun 9:30-16:30, is about 3 hours by car from Nagoya. Tel.
0265-39-2205 (Japanese or English).