On June 5, 1920, a shallow magnitude 8.2 earthquake struck offshore

Hualien County Hualien County (Mandarin Wade–Giles: Hua¹-lien² Hsien⁴; Pīnyīn: ''Huālián Xiàn''; Hokkien POJ: ''Hoa-lian-koān'' or ''Hoa-liân-koān''; Hakka PFS: ''Fâ-lièn-yen''; Amis: ''Kalingko'') is a county on the east coast of Taiwan. It ...

Empire of Japan The also known as the Japanese Empire or Imperial Japan, was a historical nation-state and great power that existed from the Meiji Restoration in 1868 until the enactment of the post-World War II 1947 constitution and subsequent fo ...

(now

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

). It is currently the largest earthquake in

's modern history.

Tectonic summary

is located within a complex zone of convergence between the

Philippine The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

and

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 ...

s. Off the island's east coast, these plates converge at a rate of 75 mm per year. To the south of Taiwan,

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 ultramafic cumu ...

of the Eurasian Plate is

subducting 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 ...

beneath the Philippine Plate, creating an

island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

, the Luzon Arc. At Taiwan the oceanic crust has all been subducted and the arc is colliding with

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic 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 ''sial'' be ...

of the Eurasian Plate. To the north of Taiwan the Philippine Sea Plate is in contrast subducting beneath the Eurasian Plate, forming the Ryukyu Arc.

Earthquake

The earthquake had a moment-magnitude of 8.2 according to the International Seismological Centre. Lower-end estimates of the moment magnitude yielded a value of 7.7 ± 0.2, which would still make it the largest in Taiwan. The USGS ShakeMap shows all areas of

felt shaking of between V and VII on the

Modified Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

. The shaking was also felt in southeast

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, the island of

Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as ...

in the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

, and southwest

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. The source fault responsible for the earthquake has not been conclusively identified, although the epicenter location suggest it was associated with the southern portion of the Ryukyu subduction zone. Based on analyzing stations in Taiwan that recorded the earthquake, the hypocenter was determined to be within the

accretionary wedge An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the do ...

at focal depth. The likely source is a rupture propagating down-dip and laterally along a splay fault associated with the subduction zone.

Impact

Eight deaths and 24 injuries were reported. 1,530 houses were affected in the cities of

Taipei Taipei (), officially Taipei City, is the capital and a special municipality of the Republic of China (Taiwan). Located in Northern Taiwan, Taipei City is an enclave of the municipality of New Taipei City that sits about southwest of the n ...

, Taitung,

Hsinchu Hsinchu (, Chinese: 新竹, Pinyin: ''Xīnzhú'', Wade–Giles: ''Hsin¹-chu²'') is a city located in northwestern Taiwan. It is the most populous city in Taiwan Province not among the special municipalities, with estimated 450,655 inhabi ...

and Taoyuan, of which 273 were destroyed, and 277 others were severely damaged.

References

{{Earthquakes in Taiwan 1920 earthquakes Earthquakes in Taiwan Hualien City Hualien County History of Taiwan 1920 in Taiwan

Tectonic summary

Earthquake

Impact

See also

References