1498 Meiō Nankaidō earthquake
Encyclopedia
The 1498 Meiō Nankaidō earthquake occurred off the coast of Nankai
, Japan, at about 08:00 local time on 20 September, 1498. It had a magnitude estimated at 8.6 MS
and triggered a large tsunami
. The death toll associated with this event is uncertain, but between 26,000 and 31,000 casualties were reported.
, 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 1498 event, the earthquake is thought to have ruptured segments C, D and E and possibly A and B. If both parts of the megathrust ruptured, the events were either simultaneous, or close enough in time, to not be distinguished by historical sources.
in the northeast to Kii Peninsula
in the southwest. A tsunami was recorded in Suruga Bay
and at Kamakura
, where it destroyed the building housing the statue of the Great Buddha at Kōtoku-in
. There is also evidence of severe shaking from records of ground liquefaction
in the Nankai
area. Tsunami deposit
s attributed to this earthquake have been described from the coastal plains around the Sagami Trough
and the Izu Peninsula
.
Uplift of the seafloor of up to 4 m has been estimated for this earthquake, with a much smaller subsidence near the coast. Lake Hamana
became a brackish lake because the tsunami broke shoal between the lake and the Pacific Ocean
(Enshū Nada).
Nankaido
The , literally meaning "southern sea road," is a Japanese term denoting both an ancient division of the country and the main road running through it. The road connected provincial capitals in this region...
, Japan, at about 08:00 local time on 20 September, 1498. It had a magnitude estimated at 8.6 MS
Surface wave magnitude
The surface wave magnitude scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements in Rayleigh surface waves that travel primarily along the uppermost layers of the earth...
and triggered a large 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...
. The death toll associated with this event is uncertain, but between 26,000 and 31,000 casualties were reported.
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 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 1498 event, the earthquake is thought to have ruptured segments C, D and E and possibly A and B. If both parts of the megathrust ruptured, the events were either simultaneous, or close enough in time, to not be distinguished by historical sources.
Characteristics
Severe shaking caused by this earthquake was recorded from Bōsō PeninsulaBoso Peninsula
thumb|Locationthumb|Landsat image with high-resolution data from Space Shuttle is a peninsula in Chiba prefecture on Honshū, the largest island of Japan. It forms the eastern edge of Tokyo Bay, separating it from the Pacific Ocean....
in the northeast to Kii Peninsula
Kii 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...
in the southwest. A tsunami was recorded in Suruga Bay
Suruga Bay
Suruga Bay is a bay on the Pacific coast of Honshū in Shizuoka Prefecture, Japan. It is situated north of an imaginary line joining Omaezaki Point and Irōzaki Point at the tip of the Izu Peninsula and surrounded by Honshū to the southwest and west and the Izu Peninsula to the east.-Geology:Suruga...
and at Kamakura
Kamakura, Kanagawa
is a city located in Kanagawa Prefecture, Japan, about south-south-west of Tokyo. It used to be also called .Although Kamakura proper is today rather small, it is often described in history books as a former de facto capital of Japan as the seat of the Shogunate and of the Regency during the...
, where it destroyed the building housing the statue of the Great Buddha at Kōtoku-in
Kotoku-in
is a Buddhist temple of the Jōdo-shū sect in the city of Kamakura in Kanagawa Prefecture, Japan.The temple is renowned for its , a monumental outdoor bronze statue of Amida Buddha which is one of the most famous icons of Japan.- The Great Buddha :...
. There is also evidence of severe shaking from records of ground 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....
in the Nankai
Nankaido
The , literally meaning "southern sea road," is a Japanese term denoting both an ancient division of the country and the main road running through it. The road connected provincial capitals in this region...
area. Tsunami deposit
Tsunami deposit
A tsunami deposit is a sedimentary unit deposited as the result of of a tsunami. Such deposits may be left onshore during the inundation phase or offshore during the 'backwash' phase. Such deposits are being used to identify past tsunami events and thereby better constrain estimates of both...
s attributed to this earthquake have been described from the coastal plains around the Sagami Trough
Sagami Trough
The also Sagami Trench, Sagami Megathrust, or Sagami Subduction Zone is a 210-mile long trough where the Kanto earthquakes of 1703 , 1855 and 1923 arose. It stretches from the Boso Triple Junction where it meets the Japan Trench to Sagami Bay. It runs north of the Izu Islands chain and the...
and the 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...
.
Uplift of the seafloor of up to 4 m has been estimated for this earthquake, with a much smaller subsidence near the coast. Lake Hamana
Lake Hamana
in Shizuoka Prefecture is Japan's tenth largest lake . It spans the boundaries of the cities of Hamamatsu and Kosai.-Data:The lake has an area of 65.0 km² and holds 0.35 km³ of water. Its circumference is 114 km. At its deepest point, the water is 16.6 m deep...
became a brackish lake because the tsunami broke shoal between the lake and the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
(Enshū Nada).