1707 Hōei earthquake
Encyclopedia
The 1707 Hōei earthquake, which occurred at 14:00 local time on October 28, 1707, was the largest in Japanese history until the 2011 Tōhoku earthquake
surpassed it. It caused moderate to severe damage throughout southwestern Honshu
, Shikoku
and southeastern Kyūshū
. The earthquake and the resulting destructive tsunami
, caused more than 5,000 casualties. This event ruptured all of the segments of the Nankai megathrust simultaneously, the only earthquake known to have done this, with an estimated magnitude
of 8.6 ML. It may also have triggered the last eruption
of Mount Fuji
some 49 days later.
, 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 1,300 years. Megathrust earthquakes on this structure tend to occur in pairs, with a relatively short time gap between them. In addition to the two events in 1854, there were similar earthquakes in 1944 and 1946. In each case, the northeastern segment ruptured before the southwestern segment. In the 1707 event, the earthquakes were either simultaneous, or close enough in time, to not be distinguished by historical sources.
was triggered by the earthquake, the Ohya slide in Shizuoka
. This landslide, one of the three largest in Japan, involved an area of 1.8 km2, with an estimated volume of 120 million m3. The Nara
Basin shows evidence of liquefaction
caused by this event.
and Ansei-Nankai earthquakes
, based on several observations. The uplift at Cape Muroto, Kōchi
is estimated at 2.3 m in 1707 compared to 1.5 m in 1854, the presence of an area of seismic intensity of 6–7 on the JMA scale
in Kawachi
Plain, the degree of damage and inundations heights for the corresponding tsunami and records of tsunami at distant locations, such as Nagasaki
and Jeju-do
, South Korea
.
2011 Tōhoku earthquake and tsunami
The 2011 earthquake off the Pacific coast of Tohoku, also known as the 2011 Tohoku earthquake, or the Great East Japan Earthquake, was a magnitude 9.0 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday, 11 March 2011, with the epicenter approximately east...
surpassed it. It caused moderate to severe damage throughout southwestern Honshu
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...
, Shikoku
Shikoku
is the smallest and least populous of the four main islands of Japan, located south of Honshū and east of the island of Kyūshū. Its ancient names include Iyo-no-futana-shima , Iyo-shima , and Futana-shima...
and southeastern Kyūshū
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....
. The earthquake and the resulting destructive tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
, caused more than 5,000 casualties. This event ruptured all of the segments of the Nankai megathrust simultaneously, the only earthquake known to have done this, with an estimated magnitude
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
of 8.6 ML. It may also have triggered the last eruption
Historic eruptions of Mount Fuji
Mount Fuji is the tallest volcano in Japan.The mountain as it appears now is the "New Fuji volcano", which began to erupt about 10,000 years ago. Under the "New Fuji volcano" lie the "Komitake volcano", which became active 700,000 years ago, and the "Old Fuji volcano", which was active between...
of Mount Fuji
Mount Fuji
is the highest mountain in Japan at . An active stratovolcano that last erupted in 1707–08, Mount Fuji lies about south-west of Tokyo, and can be seen from there on a clear day. Mount Fuji's exceptionally symmetrical cone is a well-known symbol of Japan and it is frequently depicted in art and...
some 49 days later.
Background
The southern coast of Honshu 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 1,300 years. Megathrust earthquakes on this structure tend to occur in pairs, with a relatively short time gap between them. In addition to the two events in 1854, there were similar earthquakes in 1944 and 1946. In each case, the northeastern segment ruptured before the southwestern segment. In the 1707 event, the earthquakes were either simultaneous, or close enough in time, to not be distinguished by historical sources.
Damage
29,000 houses were destroyed and there were more than 5,000 casualties. At least one major landslideLandslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
was triggered by the earthquake, the Ohya slide in Shizuoka
Shizuoka Prefecture
is a prefecture of Japan located in the Chūbu region on Honshu island. The capital is the city of Shizuoka.- History :Shizuoka prefecture was formed from the former Tōtōmi, Suruga and Izu provinces.The area was the home of the first Tokugawa Shogun...
. This landslide, one of the three largest in Japan, involved an area of 1.8 km2, with an estimated volume of 120 million m3. The Nara
Nara Prefecture
is a prefecture in the Kansai region on Honshū Island, Japan. The capital is the city of Nara.-History:The present-day Nara Prefecture was created in 1887, making it independent of Osaka Prefecture....
Basin shows evidence of liquefaction
Soil liquefaction
Soil liquefaction describes a phenomenon whereby a saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid....
caused by this event.
Earthquake
The magnitude of the 1707 event exceeded that of both the 1854 Ansei-Tōkai1854 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...
and Ansei-Nankai earthquakes
1854 Ansei-Nankai earthquake
The 1854 Ansei-Nankai earthquake occurred at about 16:00 local time on 24 December, 1854. It had a magnitude of 8.4 and caused a damaging tsunami...
, based on several observations. The uplift at Cape Muroto, Kōchi
Kochi Prefecture
is a prefecture of Japan located on the south coast of Shikoku. The capital is the city of Kōchi.- History :Prior to the Meiji Restoration, Kōchi was known as Tosa Province and was controlled by the Chosokabe clan in the Sengoku period and the Yamauchi family during the Edo period.- Geography...
is estimated at 2.3 m in 1707 compared to 1.5 m in 1854, the presence of an area of seismic intensity of 6–7 on the JMA scale
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...
in Kawachi
Kawachi Province
was a province of Japan in the eastern part of modern Osaka Prefecture. It originally held the southwestern area that was split off into Izumi Province...
Plain, the degree of damage and inundations heights for the corresponding tsunami and records of tsunami at distant locations, such as Nagasaki
Nagasaki
is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. Nagasaki was founded by the Portuguese in the second half of the 16th century on the site of a small fishing village, formerly part of Nishisonogi District...
and Jeju-do
Jeju-do
Jeju-do is the only special autonomous province of South Korea, situated on and coterminous with the country's largest island. Jeju-do lies in the Korea Strait, southwest of Jeollanam-do Province, of which it was a part before it became a separate province in 1946...
, South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
.