Plate boundary between the Amurian and Okhotsk plates in East Asia
The eastern margin of the Sea of Japan is a zone of concentrated geological strain which extends several hundred kilometers and north–south along the eastern margin of the Sea of Japan. The margin has undergone convergence tectonics since the end of the Pliocene.[1][2] It is believed to be an incipient subduction zone which defines the tectonic boundary between the Amurian and Okhotsk plates. This geological zone is seismically active and has been the source of destructive tsunamis. The feature runs off the west coast of Honshu, passes west of the Shakotan Peninsula on Hokkaido and through the Strait of Tartary, between Sakhalin and mainland Russia.
The Sea of Japan represents a back-arc basin that formed via geological rifting of continental crust from the late Oligocene to middle Miocene (28–13 million years ago).[3] The Sea of Japan can be divided into sub-basins; the Japan Basin, Yamato Basin and Tsushima Basin. Seafloor spreading in the Sea of Japan was restricted to the Japan Basin and ceased by the middle Miocene.[4]
Following the end of seafloor spreading, its eastern margin experienced weak compression between 10 and 3.5 million years ago. Crustal shortening has been ongoing in the eastern margin and back-arc region of the Northeastern Japan Arc since 3.5 million years ago. This deformation is attributed to east–west compressive forces, forming fold and thrust belts along the eastern margin. The southern margin was subjected to north–south or northwest–southeast compression about 8–5 million years ago. Presently, the southern margin hosts mainly strike-slip faults.[4]
The margin is located at the boundary marking the Amurian and Okhotsk microplates. Oceanic lithosphere from the Sea of Japan located on the Amurian Plate converges with the Japanese archipelago on the Okhotsk Plate. A Wadati–Benioff zone which is evidence for subduction, is absent in the zone, hence subduction is doubtful. However, it may be an incipient eastward-dipping subduction zone.[5] In 1983, it was proposed that subduction along the eastern margin commenced about 1–2 million years ago.[6]
The basis for defining this tectonic boundary is the occurrence of large magnitude 7 or greater earthquakes along a linear zone from offshore Niigata Prefecture to off the west coast of Hokkaido.[7] Following the 1983 Nihonkai-Chubu earthquake,
the idea of a young plate boundary was proposed, but its mechanism is unknown—it has been proposed as a transform boundary or collision zone.[8]
The eastern margin of the Sea of Japan was the source of historically destructive earthquakes and tsunamis. These events were considered intraplate earthquakes until 1983 when the plate boundary theory was proposed.[11] The associated geological faults related to the opening of the sea and compressive forces along the eastern margin influence seismic activity. Large earthquakes in 1833, 1940, 1964, 1983, and 1993 were the result of reverse faulting associated with the present deformation. The Sea of Japan is considered one of the world's most seismically active back-arc basins.[12]
About 2,000 people killed along the west coast of Japan from the resulting tsunami. Homes and fishing boats destroyed in Korea.[15] Tsunami magnitude calculated at Mt 8.4; largest tsunami in the region.[16]
At least 19 people killed, 732 homes destroyed and 1,423 damaged.[21] Caused 2 m (6 ft 7 in) of uplift on the Ogi Peninsula, exposing pillow lava from the Miocene.[22]
Ten people killed, 24 injured, and many homes and fishing boats damaged or destroyed in Hokkaido, North Korea and Russia.[30] Tsunami recorded with a maximum height of 5 m (16 ft) at Kamenka, Primorsky Krai.[31]
Felt at Haboro and Rumoi. Tsunami recorded with a height of 2 m (6 ft 7 in) at Wakkanai and Rishiri Island; 0.7 m (2 ft 4 in) at Haboro and several tens of centimeters at Otaru. Minor damage.[32][33]
Rockfalls and landslides on Moneron Island. Damage to buildings in Shebunino and Gomozavodsk on Sakhalin. Felt VII–VIII (MSK) on Moneron Island and VII (MMI) in southern Sakhalin.[35] Tsunami recorded with a maximum height of 2 m (6 ft 7 in) at Shebunino, Sakhalin.[36]
Heavy damage due to liquefaction. At least 104 people dead—4 as a direct effect of the earthquake. One hundred deaths attributed to the tsunami including three deaths in South Korea.[37]
At least 230 people killed including 165 on Okushiri. Tsunami recorded 30.6 m (100 ft) on the southern coast of Okushiri; 10 m (33 ft) along the Hokkaido coast; also recorded in Russia and South Korea. Considerable damage from fires, landslides and tsunami. Three people missing along Russia's southeastern coast.
Occurred on a west-dipping reverse fault as opposed to east-dipping faults involved in large Sea of Japan earthquakes. Three tsunami waves measuring up to 3.2 m (10 ft).[45] Two people killed, ten injured and severe damage occurred in Nevelsk. Over half of the town's 11,000 residents displaced. Maximum MSK-64 intensity VIII.[46]
Large earthquakes with epicenters offshore and north of the Noto Peninsula are mostly accompanied by tsunamis. These events have recurrence intervals of 1,000 years.[54] Due to their closer proximity to land, the accompanying tsunamis require a shorter time arriving compared to earthquakes along Japan's Pacific coast.[55] These earthquakes tend to generate considerably large tsunamis.[56]
The 75 km (47 mi)-long Akita-oki seismic gap lies off the coast of Akita Prefecture. This plate-boundary segment is located between the rupture zones of the 1833 and 1983 earthquakes and has not experienced a major earthquake during historical times. It has the potential to produce a magnitude 7.5 earthquake, probably by the end of the 21st century. Another seismic gap of 50 km (31 mi) length is thought to exist off the coast of Hokkaido between the 1940 and 1993 rupture zones. [11]
^Uda, Tsuyoshi; Hiramatsu, Yukiko; Azuma, Shinji. "新潟平野~信濃川構造帯の地震と活断層" [Earthquakes and Active Faults in the Niigata Plain-Shinanogawa Tectonic Zone] (PDF) (in Japanese). Niigata University. Archived from the original(PDF) on 2 February 2016. {{cite journal}}: Cite journal requires |journal= (help)
^Yukinobu Okamura (1998). 日本海東縁海域の活構造およびその地震との関係 [Active structure in the eastern margin of the Sea of Japan and its relationship with earthquakes] (PDF). Geological Survey Monthly Report (in Japanese). 49 (1). Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology. Archived(PDF) from the original on 2 April 2022. Retrieved 31 March 2021.
^Okada, R.; Umeda, K.; Kamataki, T.; Sawai, Y.; Matsumoto, D.; Shimada, Y.; Ioki, K. (2022). "Geological record of 18th and 19th century tsunamis along the Japan Sea coast of Tsugaru Peninsula, northwestern Japan". Marine Geology. 453: 106905. Bibcode:2022MGeol.45306905O. doi:10.1016/j.margeo.2022.106905. S2CID252657984.
^Ota, Y.; Matsuda, T.; Naganuma, K. (1976). "佐渡小木地震 (1802年) による土地隆起量の分布とその意義" [Distribution and Significance of Land Uplift Due to the Sado Ogi Earthquake (1802)]. Earthquake Series 2. 29 (1): 55–70. doi:10.4294/zisin1948.29.1_55. Archived from the original on 2019-02-13. Retrieved 2023-01-11.
^Mizuta, T.; Kagami, H. (2010). "1939.5.1男鹿地震の被害分布に関する文献調査" [Literature survey on the damage distribution of the 1939.5.1 Oga earthquake]. Architectural Institute of Japan Technical Report Collection. 16 (33): 817–820. Archived from the original on 2021-08-21. Retrieved 2023-01-11.
^"Niigata earthquake of 1964"(PDF). Japan National Committee on Earthquake Engineering. Archived(PDF) from the original on 21 September 2021. Retrieved 11 January 2023.
^National Earthquake Information Center (4 August 2000). "M 6.8 - 35 km SSE of Uglegorsk, Russia". United States Geological Survey. Archived from the original on 20 June 2022. Retrieved 11 January 2023.
^Konovalov, A. V.; Nagornykh, T. V.; Safonov, D. A.; Lomtev, V. L. (5 December 2015). "Nevelsk earthquakes of August 2, 2007 and seismic setting in the southeastern margin of Sakhalin Island". Russian Journal of Pacific Geology. 9 (6): 451–466. Bibcode:2015RuJPG...9..451K. doi:10.1134/S1819714015060056. S2CID130563216.