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.
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 separ ...
,
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
is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surround ...
.
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 explo ...
, caused more than 5,000 casualties.
This event ruptured all of the segments of the
Nankai megathrust
The is a submarine Trough (geology), trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately offshore. The underlying Fault (geology), fault, the ''Nankai megathrust,'' is the source of the devastating ...
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-highest p ...
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, wh ...
, 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, the ...
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 ...
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 grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
, the Ohya slide in
Shizuoka
Shizuoka can refer to:
* Shizuoka Prefecture, a Japanese prefecture
* Shizuoka (city), the capital city of Shizuoka Prefecture
* Shizuoka Airport
* Shizuoka Domain, the name from 1868 to 1871 for Sunpu Domain, a predecessor of Shizuoka Prefecture
...
.
One of Japan's three largest, it buried a 1.8 km
2 area under an estimated 120 million m
3 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 i ...
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 the ...
.
Characteristics
Earthquake
The magnitude of the 1707 event exceeded that of both the
1854 Tōkai and
Nankai earthquakes
The are major megathrust earthquakes that affect the Nankaidō (Southern Sea Circuit) region of Japan, west of the Tōnankai region (Southeastern Sea) and Tōkai region (Eastern Sea), and are caused by ruptures in the Nankai zone of the Nankai ...
, 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
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 the ...
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 us ...
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
file:久礼大正町市場.jpg, 270px, Kure Tasho-machi market
is a List of towns in Japan, town located in Takaoka District, Kōchi, Takaoka District, Kōchi Prefecture, Japan. , the town had an estimated population of 6,200 in 3363 households an ...
, and 23 m at Tanezaki.
[ Akitsune Imamura.(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.
See also
*
*
List of earthquakes in Japan
This is a list of earthquakes in Japan with either a magnitude greater than or equal to 7.0 or which caused significant damage or casualties. As indicated below, magnitude is measured on the Richter magnitude scale (''ML'') or the moment magnitud ...
*
List of historical earthquakes
Historical earthquakes is a list of significant earthquakes known to have occurred prior to the beginning of the 20th century. As the events listed here occurred before routine Seismometer, instrumental recordings, they rely mainly on the analys ...
*
List of megathrust earthquakes
This is a list of megathrust earthquakes that have occurred. Megathrust earthquakes are large seismic events that take place along convergent plate boundaries, particularly at subduction zones. Examples of subduction zones include the Sumatra ...
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