The struck south-central Japan at 14:00 local time on 28 October. It was the largest earthquake in Japanese history until it was surpassed by the

2011 Tōhoku earthquake Eleven or 11 may refer to: * 11 (number), the natural number following 10 and preceding 12 * one of the years 11 BC, AD 11, 1911, 2011, or any year ending in 11 Literature * ''Eleven'' (novel), a 2006 novel by British author David Llewellyn * ...

. It caused moderate to severe damage throughout southwestern

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island ...

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), ...

and southeastern Kyūshū. The earthquake, and the resulting destructive

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

, caused more than 5,000 casualties. This event ruptured all of the segments of the

Nankai megathrust The is a submarine trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately offshore. The underlying fault, the ''Nankai megathrust,'' is the source of the devastating Nankai megathrust earthquakes, w ...

simultaneously, the only earthquake known to have done this, with an estimated

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of 8.6 or 8.7 . It possibly also triggered the last eruption of

Mount Fuji , or Fugaku, located on the island of Honshū, is the highest mountain in Japan, with a summit elevation of . It is the second-highest volcano located on an island in Asia (after Mount Kerinci on the island of Sumatra), and seventh-highes ...

49 days later.

Hōei was a after Genroku and before Shōtoku''.'' This period spanned the years from March 1704 through April 1711. The reigning emperors were and . Change of era * 1704 : In reaction to the Great Genroku earthquake in Genroku 16, the era name w ...

(宝永) was the era spanning the years from March 1704 through April 1711.

Tectonic setting

The southern coast of Honshu runs parallel to the

Nankai Trough The is a submarine trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately offshore. The underlying fault, the ''Nankai megathrust,'' is the source of the devastating Nankai megathrust earthquakes, w ...

, which marks the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

of the

Philippine Sea Plate The Philippine Sea Plate or the Philippine Plate is a tectonic plate comprising oceanic lithosphere that lies beneath the Philippine Sea, to the east of the Philippines. Most segments of the Philippines, including northern Luzon, are part of ...

beneath the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

. Movement on this

convergent plate boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a p ...

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 two events in 1854, a similar pair occurred in 1944 and 1946. In both instances, 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

The earthquake caused more than 5,000 casualties, destroyed 29,000 houses, and triggered at least one major

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, ...

, the Ohya slide in Shizuoka. One of Japan's three largest, it buried a 1.8 km² area under an estimated 120 million m³ of debris. The

Nara The National Archives and Records Administration (NARA) is an " independent federal agency of the United States government within the executive branch", charged with the preservation and documentation of government and historical records. It ...

Basin shows evidence of event-induced

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of t ...

Characteristics

Earthquake

The magnitude of the 1707 event exceeded that of both the 1854 Tōkai and Nankai earthquakes, based on several observations. The uplift at Cape Muroto,

Kōchi Kochi is a city in Kerala, India. Kochi or Kōchi may also refer to: People * Kochi people, a predominantly Pashtun nomadic people of Afghanistan * , a Japanese surname: ** Arata Kochi (born 1948 or 1949), Japanese physician and World Health Org ...

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 is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. It became the sole port used for trade with the Portuguese and Dutch during the 16th through 19th centuries. The Hidden Christian Sites in th ...

and Jeju-do,

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

. The length of the rupture has been estimated from the modelling of the observed tsunami and the location of

tsunami deposit A tsunami deposit (the term tsunamiite is also sometimes used) is a sedimentary unit deposited as the result of a tsunami. Such deposits may be left onshore during the inundation phase or offshore during the 'backwash' phase. Such deposits are u ...

s. Initial estimates of 605 km, based on four segments rupturing failed to explain tsunami deposits discovered at the western end of the trough. Including an additional area at the southwestern end, part of the so-called Hayuga-nada segment, gave a better match, with a total rupture length in the range 675–700 km.

Tsunami

Along the southwestern coast of Kōchi, run-up heights averaged 7.7 m with up to 10 m in places; In Japanese. 25.7 m high at Kure, Nakatosa, Kōchi, and 23 m at Tanezaki.

Akitsune Imamura was a Japanese seismologist. As a University of Tokyo seismologist he represented a new generation of scientists, trained by Western experts. He who predicted the timing and magnitude of the 1923 Great Kantō earthquake 16 years in advance. Bo ...

.(1938
土佐に於ける宝永・安政両度津浪の高さ
地震第1輯, 10, 394–404. in Japanese.

Eruption of Mount Fuji

Evidence suggests that changes in stress caused by large earthquakes may be sufficient to trigger volcanic eruptions, assuming that the magma system involved is close to a critical state. The 1707 earthquake may have triggered a shift in static stress that led to pressure changes in the magma chamber beneath Mount Fuji: the volcano erupted on 16 December 1707, 49 days after the quake.

References

{{DEFAULTSORT:1707 Hoei earthquake 1707 earthquakes Hoei earthquake 1707 tsunamis Megathrust earthquakes in Japan Tsunamis in Japan Mount Fuji Earthquakes of the Edo period 1707 disasters in Asia 18th-century disasters in Japan