1944 Tōnankai earthquake
Encyclopedia
The 1944 Tōnankai earthquake occurred at 13:35 local time (04:35 UTC
) on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale
and a maximum felt intensity of greater than 5 shindo
(about VIII (destructive) on the Mercalli intensity scale
). It triggered a large tsunami that caused serious damage along the coast of Wakayama Prefecture
and the Tōkai region
. Together the earthquake and tsunami caused 1,223 casualties.
particularly at Shingū
and Temma. A total of 26,146 houses were destroyed by the shaking, including 11 that burned down and a further 3,059 houses were destroyed by the tsunami. Nearly 47,000 houses were seriously damaged by the combined effects of the earthquake and tsunami. 1,223 people were killed and a further 2,135 were seriously injured.
, which marks the subduction
of the Philippine Sea Plate beneath the Eurasian Plate
. Movement on this convergent plate boundary leads to many earthquakes, some of them of megathrust type
. The Nankai megathrust has five distinct segments (A-E) that can rupture independently, the segments have ruptured either singly or together repeatedly over the last 1300 years. Megathrust earthquakes on this structure tend to occur in pairs, with a relatively short time gap between them. The 1944 event, which ruptured the C & D segments was followed two years late by the 1946 Nankaidō earthquake
, rupturing segments A & B. In addition to these two events, there were two similar earthquakes in 1854. In each case the northeastern segment ruptured before the southwestern segment.
coast. Run-ups in excess of 5 m were also recorded at several locations along the coasts of Mie
and Wakayama Prefecture
s. The tsunami was observed along the Pacific coast of Japan from Izu Peninsula
to Kyushu
, and recorded by tide gauges from Alaska to Hawaii.
.
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
and a maximum felt intensity of greater than 5 shindo
Japan Meteorological Agency seismic intensity scale
The Japan Meteorological Agency seismic intensity scale is a seismic scale used in Japan and Taiwan to measure the intensity of earthquakes. It is measured in units of...
(about VIII (destructive) on the Mercalli intensity scale
Mercalli intensity scale
The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...
). It triggered a large tsunami that caused serious damage along the coast of Wakayama Prefecture
Wakayama Prefecture
is a prefecture of Japan located on the Kii Peninsula in the Kansai region on Honshū island. The capital is the city of Wakayama.- History :Present-day Wakayama is mostly the western part of the province of Kii.- 1953 Wakayama Prefecture flood disaster :...
and the Tōkai region
Tokai region
The is a sub-region of the Chūbu region in Japan that runs along the Pacific Ocean. The name means "East sea" and comes from the Tōkaidō, one of the Edo Five Routes...
. Together the earthquake and tsunami caused 1,223 casualties.
Damage
There was severe damage from the earthquake on the eastern side of the Kii PeninsulaKii Peninsula
The is the largest peninsula on the island of Honshū in Japan. The area south of the “Central Tectonic Line” is called Nankii , and includes the most poleward living coral reefs in the world due to the presence of the warm Kuroshio Current, though these are threatened by global warming and human...
particularly at Shingū
Shingu, Wakayama
is a city located in Wakayama, Japan.As of May 1, 2011, the city has an estimated population of 32,288, with a household number of 16,003, and the density of 126.41 persons per km². The total area is 255.43 km²....
and Temma. A total of 26,146 houses were destroyed by the shaking, including 11 that burned down and a further 3,059 houses were destroyed by the tsunami. Nearly 47,000 houses were seriously damaged by the combined effects of the earthquake and tsunami. 1,223 people were killed and a further 2,135 were seriously injured.
Tectonic setting
The southern coast of Honshū runs parallel to the Nankai TroughNankai Trough
The Nankai Trough is a submarine trough located south of Japan's island of Honshū, extending approximately 900 km offshore. In plate tectonics, the Nankai Trough marks a subduction zone that is caused by subduction of the Philippine Sea Plate beneath Japan, part of the Eurasian plate...
, which marks the subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
of the Philippine Sea Plate beneath the Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
. Movement on this convergent plate boundary leads to many earthquakes, some of them of megathrust type
Megathrust earthquake
Megathrust earthquakes occur at subduction zones at destructive plate boundaries , where one tectonic plate is forced under another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, these earthquakes are among the world's largest, with moment magnitudes ...
. The Nankai megathrust has five distinct segments (A-E) that can rupture independently, the segments have ruptured either singly or together repeatedly over the last 1300 years. Megathrust earthquakes on this structure tend to occur in pairs, with a relatively short time gap between them. The 1944 event, which ruptured the C & D segments was followed two years late by the 1946 Nankaidō earthquake
1946 Nankaido earthquake
The 1946 Nankaidō earthquake was a great earthquake in Nankaidō, Japan. It occurred on December 20, 1946 at 19:19 UTC. The earthquake measured between 8.1 and 8.4 on the moment magnitude scale, and was felt from Northern Honshū to Kyūshū...
, rupturing segments A & B. In addition to these two events, there were two similar earthquakes in 1854. In each case the northeastern segment ruptured before the southwestern segment.
Earthquake
Felt intensities of greater than Shindo 5 were recorded along the southern coast of Honshū, with Shindo 3–4 in Tokyo. The observed teleseismic response and tsunami records have been matched using a rupture area of 220 x 140 km and a maximum displacement of 2.3 m. It has been suggested that splay faults, linking back into the plate interface, have had an important role in generating large tsunamigenic earthquakes along the Nankai trough. The 1944 event could have occurred on such a splay fault.Tsunami
The maximum recorded wave height was 10 m on the KumanoKumano, Mie
is a city located in Mie, Japan.The city was founded on November 3, 1954.On November 1, 2005 the town of Kiwa, from Minamimuro District, was merged into Kumano....
coast. Run-ups in excess of 5 m were also recorded at several locations along the coasts of Mie
Mie Prefecture
is a prefecture of Japan which is part of the Kansai regions on Honshū island. The capital is the city of Tsu.- History :Until the Meiji Restoration, Mie prefecture was known as Ise Province and Iga Province....
and Wakayama Prefecture
Wakayama Prefecture
is a prefecture of Japan located on the Kii Peninsula in the Kansai region on Honshū island. The capital is the city of Wakayama.- History :Present-day Wakayama is mostly the western part of the province of Kii.- 1953 Wakayama Prefecture flood disaster :...
s. The tsunami was observed along the Pacific coast of Japan from Izu Peninsula
Izu Peninsula
The is a large mountainous peninsula with deeply indented coasts to the west of Tokyo on the Pacific coast of the island of Honshū, Japan. Formerly the eponymous Izu Province, Izu peninsula is now a part of Shizuoka Prefecture...
to Kyushu
Kyushu
is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....
, and recorded by tide gauges from Alaska to Hawaii.
Future seismic hazard
The segment of the megathrust to the east of the rupture area for the 1944 earthquake has not ruptured since 1854 and the likelihood of a 'Tokai earthquake' is considered to be high. There is no evidence that this segment has ruptured on its own in the past, although this cannot be ruled out. Any rupture of segment E may also include segments C & D, possibly causing a repeat of the damaging 1854 Ansei-Tokai earthquake1854 Ansei-Tōkai earthquake
The 1854 Ansei-Tōkai earthquake was the first of the Ansei Great Earthquakes . It occurred at about 09:00 local time on 23 December, 1854. It had a magnitude of 8.4 and caused a damaging tsunami...
.