Andes Cordillera mountains near the town of Valdivia. This generated a tsunami
and waves of less than 1 m on the sea floor, but when the bottom waves reached
shallow water depths the wave’s crest was more than 20 m high and killed more
than 2,000 people (Cromie 1962).
On December 26, 2004, more than 100 years after the Krakatau volcanic
eruption in Indonesia, the Sumatra-Java trench was again the site of a large
earthquake with a magnitude of 9.3 on the Richter scale. This earthquake generated
a tsunami wave that was felt on the other side of the Indian Ocean striking the coast
of Somalia in eastern Africa and killing a total of about 300,000. The epicenter was
located on the northern portion of the Sumatra–Java trench at about 100 km away
from the coast of Sumatra near the island of Simelue where the relatively denser
Indo-Australian plate is moving beneath the lighter Burma-Malaysian plate.
On June 3, 2011, an earthquake started at 58 min after midnight and lasted
about 7 min extending northwestward along the Sunda trench for about 1200 km
almost reaching the coast of Myanmar (Burma) (Park et al. 2005). The faulted area
was about 100 km wide.
An earthquake with a magnitude of 7.2 was felt in the morning of November
29, 1975, in Hawaii and was monitored by the Hawaiian Volcano Observatory
located on the Kilauea Volcano (Tilling et al. 1975). The epicenter was located on
the flank of the Kilauea caldera on the sea floor at about 25 km from the town of
Halapa on the southeast coast of the island. This gave rise to sea waves as high as
12 m. Underwater landslides probably provoked the collapse of the submarine
flank of the volcano. This triggered and pushed a large wave into motion due to the
uplift of the sea floor at the base of the volcano. New open fissures 50–100 m wide
occurred at the same time on the island itself. Since the tsunami expended much of
its energy on a sparsely populated area, only two people were killed. About half an
hour after the main earthquake shock, Kilauea begun to erupt along a 500 m long
fissure formed in the caldera of the volcano. This was a quiet eruption with lava
fountaining up to a maximum of 50 m high (Head and Wilson 1989).
Of course the most famous tsunami of recent date took place on March 11,
2011, when a giant wave hit the north coast of Honshu Island in Japan and caused
an accidental nuclear catastrophe when an electric power plant in Fukushima was
infiltrated by seawater. The source of the movement of the ocean floor was an area
in the Japan trench which had been previously explored by Xavier Le Pichon
(Kaiko project, 1984–1985). Le Pichon and his colleagues knew this region was
tectonically active, so the event of an earthquake was not surprising. The magnitude of the Tohoku earthquake, which attained 9.0 on the Richter scale, was,
however, the highest magnitude ever recorded in Japan, and the results were
disastrous, as we all know.
Unfortunately, no early warning was possible since the wave hit the shore of
Japan only 51 min after the tectonic activity occurred, so the number of deaths
after the ‘‘Fukushima tsunami’’ could not have been prevented. Now, however,
man needs to take stock of the location of the world’s nuclear power plants and
decide what to do about them should they be found in tectonically active areas or
along the path of potential future tsunamis.
140
5 Earth’s Mantle Melting and Volcanism
and waves of less than 1 m on the sea floor, but when the bottom waves reached
shallow water depths the wave’s crest was more than 20 m high and killed more
than 2,000 people (Cromie 1962).
On December 26, 2004, more than 100 years after the Krakatau volcanic
eruption in Indonesia, the Sumatra-Java trench was again the site of a large
earthquake with a magnitude of 9.3 on the Richter scale. This earthquake generated
a tsunami wave that was felt on the other side of the Indian Ocean striking the coast
of Somalia in eastern Africa and killing a total of about 300,000. The epicenter was
located on the northern portion of the Sumatra–Java trench at about 100 km away
from the coast of Sumatra near the island of Simelue where the relatively denser
Indo-Australian plate is moving beneath the lighter Burma-Malaysian plate.
On June 3, 2011, an earthquake started at 58 min after midnight and lasted
about 7 min extending northwestward along the Sunda trench for about 1200 km
almost reaching the coast of Myanmar (Burma) (Park et al. 2005). The faulted area
was about 100 km wide.
An earthquake with a magnitude of 7.2 was felt in the morning of November
29, 1975, in Hawaii and was monitored by the Hawaiian Volcano Observatory
located on the Kilauea Volcano (Tilling et al. 1975). The epicenter was located on
the flank of the Kilauea caldera on the sea floor at about 25 km from the town of
Halapa on the southeast coast of the island. This gave rise to sea waves as high as
12 m. Underwater landslides probably provoked the collapse of the submarine
flank of the volcano. This triggered and pushed a large wave into motion due to the
uplift of the sea floor at the base of the volcano. New open fissures 50–100 m wide
occurred at the same time on the island itself. Since the tsunami expended much of
its energy on a sparsely populated area, only two people were killed. About half an
hour after the main earthquake shock, Kilauea begun to erupt along a 500 m long
fissure formed in the caldera of the volcano. This was a quiet eruption with lava
fountaining up to a maximum of 50 m high (Head and Wilson 1989).
Of course the most famous tsunami of recent date took place on March 11,
2011, when a giant wave hit the north coast of Honshu Island in Japan and caused
an accidental nuclear catastrophe when an electric power plant in Fukushima was
infiltrated by seawater. The source of the movement of the ocean floor was an area
in the Japan trench which had been previously explored by Xavier Le Pichon
(Kaiko project, 1984–1985). Le Pichon and his colleagues knew this region was
tectonically active, so the event of an earthquake was not surprising. The magnitude of the Tohoku earthquake, which attained 9.0 on the Richter scale, was,
however, the highest magnitude ever recorded in Japan, and the results were
disastrous, as we all know.
Unfortunately, no early warning was possible since the wave hit the shore of
Japan only 51 min after the tectonic activity occurred, so the number of deaths
after the ‘‘Fukushima tsunami’’ could not have been prevented. Now, however,
man needs to take stock of the location of the world’s nuclear power plants and
decide what to do about them should they be found in tectonically active areas or
along the path of potential future tsunamis.
140
5 Earth’s Mantle Melting and Volcanism