The 1867 Keelung earthquake occurred off the northern coast of

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

on the morning of

December 18 Events Pre-1600 * 1118 – The city of Zaragoza is conquered by king Alfonso I of Aragon from the Almoravid. * 1271 – Kublai Khan renames his empire "Yuan" (元 yuán), officially marking the start of the Yuan dynasty of Mongolia an ...

with a magnitude of 7.0. It produced strong shaking that seriously damaged the cities of

Keelung Keelung ( ; zh, p=Jīlóng, c=基隆, poj=Ke-lâng), Chilung or Jilong ( ; ), officially known as Keelung City, is a major port city in northeastern Taiwan. The city is part of the Taipei–Keelung metropolitan area with neighboring New Ta ...

and

Taipei , nickname = The City of Azaleas , image_map = , map_caption = , pushpin_map = Taiwan#Asia#Pacific Ocean#Earth , coordinates = , subdivision_type = Country ...

. A

tsunami A tsunami ( ; from , ) 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 underwater explosions (including detonations, ...

, thought to be the only confirmed destructive of its kind in Taiwan, drowned hundreds and had a run-up exceeding . The total death toll was estimated to be 580 while more than 100 were injured. It was followed by

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

s that were felt on average ten times a day.

Tectonic setting

Taiwan is situated on a complex

convergent 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 ...

between the Eurasian plate and 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 ...

. Off the northeastern coast of the island, the Philippine Sea plate

subduct Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plat ...

s northwards beneath the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Geography of Taiwan, Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi Islands, Ōsumi, Tokara Islands, Tokara and A ...

(on the overriding Eurasian plate) along the Ryukyu Trench. To the south of the island,

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramaf ...

of the Eurasian plate subducts beneath eastwards the Philippine Sea plate along the

Manila Trench The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about , in contrast with the average depth of the South China Sea of about . It i ...

. Taiwan lies at the junction of the two subduction zones, on the edge of the Asian

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...

(Eurasian plate), where the northwest–southeast convergence rate is estimated to be 7 cm/year.

Continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at Convergent boundary, convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroy ...

occurs due to convergence of the Asian

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

with continental crust of the Philippine Sea plate on the island. Continental crust of the Eurasian plate is being subducted beneath the island, forming east-dipping thrust faults.

Geology

Multiple studies have been conducted to identify the source of the earthquake and subsequent tsunami. The moment () and

local Local may refer to: Geography and transportation * Local (train), a train serving local traffic demand * Local, Missouri, a community in the United States Arts, entertainment, and media * ''Local'' (comics), a limited series comic book by Bria ...

() magnitudes have been estimated to be 7.0 and 6.8, respectively. Due to the unusually large tsunami, several studies have suggested a

submarine landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting stres ...

or an eruption of the nearby

Tatun Volcanic Group The Tatun Volcanic Group () constitutes a group of volcanoes located in northern Taiwan. It is located 15 km north of Taipei, and lies to the west of Keelung. It just adjoins the northern coast of the Taiwan island. The volcanic group was a ...

was the source of the tsunami. The lack of historical documentation of the tsunami effects made identifying the fault difficult. Academics have associated the earthquake with a rupture along the Shanchiao Fault, a northeast–southwest trending

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

. The fault runs onshore from the Taipei area to Jinshan for a length of , and further extends offshore for another . The fault dips towards the southeast at varying angles of 80° onshore to 62° offshore. It was also associated with an earthquake and tsunami in 1694. The Jinshan area formed due to rifting during the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

. In a 2017 study by Sugawara and others, modelling of the earthquake suggest a 7.24 event with coseismic slip of 6 meters was required to reproduce the tsunami heights reported. The modelled earthquake involved a rupture on the onshore and offshore segments. An earlier study (2016) by Cheng and others estimated a rupture offshore at a depth of was consistent with the seismic intensity and tsunami reports. The modelled earthquake had a of 7.0 and an

epicenter The epicenter (), epicentre, or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Determination The primary purpose of a ...

located at .

Earthquake

The earthquake occurred at 09:00 or 10:00

local time Local time is the time observed in a specific locality. There is no canonical definition. Originally it was mean solar time, but since the introduction of time zones it is generally the time as determined by the time zone in effect, with daylight s ...

and produced shaking that lasted 15–30 seconds. In Taipei's

Shilin District Shilin District (also spelled Shihlin District, zh, t=士林區, p=Shìlínqū, poj=Sū-lîm-khu) is a district of Taipei. The central command center of the Republic of China Navy (ROCN) is located in Shilin. History The name ''Shilin'' w ...

, many streets were damaged. Buildings collapsed in the city, killing hundreds. Major landslides occurred between Taipei and Keelung, demolishing villages. A large

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

measuring in length was reported at Huangzuishan. The landslide carved a

gorge A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tend ...

and hot sulfur-laced water flowed. Fissures formed and closed in the ground. More than half the number of homes in Jinshan collapsed. At a beach in Huanggang,

hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

s erupted to a height of . One person was killed and many were injured in Huangku when a hot spring erupted from a field. Water from the spring formed a large pond that still exists. Heavy damage was reported at Keelung where collapses buried several hundred residents. In

Tamsui Tamsui District () is a seaside district in New Taipei City, Taiwan adjacent to the Tamsui River and overlooking the Taiwan Strait. The name of the district means "fresh water" in Chinese. Although modest in size (population 189,271), Tamsui ...

, homes collapsed, killing 30, and a British merchant warehouse was extensively damaged. At a nearby town, not far from Tamsui, 150 deaths occurred. An estimated 400 people were killed near the coast. The earthquake also killed more than 300 buffaloes and pigs due to collapses. Land subsidence by between and was estimated.

Tsunami

Seawater receded approximately five minutes after the earthquake and 25 minutes later, exposed the seafloor by . The tsunami struck at 11:00 local time, killed between 70 and 80 people in Jinshan. Tsunami victims were also reported at

Yilan Yilan may refer to: China * Yilan County, Heilongjiang (依兰县), county of central Heilongjiang province, People's Republic of China * Yilan Town, Heilongjiang (依兰镇), seat of Yilan County * Yilan, Jilin (依兰镇), town in Yanji Taiwan ...

and Hualien. Many were killed after they went to the coast to collect fishes after the water receded. Over 100 were injured. A reported tsunami height of was observed at Huanggang and Shuiwei. Several

Chinese junk A junk () is a type of Chinese sailing ship characterized by a central rudder, an overhanging flat transom, watertight bulkheads, and a flat-bottomed design. They are also characteristically built using iron nails and clamps. The term applie ...

s were beached and pushed further inland while others sunk. At the harbour in Keelung, the tsunami was . The waves destroyed 200 homes. A run-up of over was estimated at Jinbaoli Old Street and Badouzi. The high run-up at Jinbaoli Old Street was due to a river which allowed waves from the sea to flow upstream. Tsunami damage at Keelung was minimal and only affected the immediate coastal parts of the city. Waves were reported on Heping Island and

Tongpan Island Tongpan Island () is an island in Tongpan Village (), Magong, Magong City, Penghu County (the Pescadores), Taiwan. Tongpan Island is about from the main island of Penghu. A ferry runs between Tongpan Island and Penghu Main Island twice a day an ...

. A

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 use ...

was found above sea level on Heping Island. A 2016 study in Jinshan found tsunami deposits up to inland. An unusual tide was observed at

Hangzhou Hangzhou, , Standard Mandarin pronunciation: ; formerly romanized as Hangchow is a sub-provincial city in East China and the capital of Zhejiang province. With a population of 13 million, the municipality comprises ten districts, two counti ...

while at the

Yangtze River The Yangtze or Yangzi ( or ) is the longest river in Eurasia and the third-longest in the world. It rises at Jari Hill in the Tanggula Mountains of the Tibetan Plateau and flows including Dam Qu River the longest source of the Yangtze, i ...

, the water level fell before rising in 48 hours. These observations are believed to be the effects of the tsunami.

Volcanic eruption

A report of a

submarine eruption Submarine eruptions are volcano eruptions which take place beneath the surface of water. These occur at constructive margins, subduction zones, and within tectonic plates due to hotspots. This eruption style is far more prevalent than subaerial ...

at the time of the earthquake and tsunami was vaguely described and published in 1917. It is thought to be the only instance of an earthquake, tsunami and eruption occurring at the same time in the region. The eruption occurred off the northeast coast of the island but nature of it is unknown.

References