Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions, Climate Change and other Natural and Man-Made Hazards and Disasters - Disaster Archaeology,

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The Earthquake and Tsunami of 26 May 1983 in the Sea of Japan / East Sea

George Pararas-Carayannis

Copyright © 2000. All Rights Reserved


INTRODUCTION

On 26 May, 1983, a major earthquake - named the "Nihonkai-chubu (Japan sea ) Earthquake of 1983 - occurred in the Central Sea of Japan (Japan Sea). The earthquake generated a major local tsunami which was destructive in Japan and Korea. Almost all of the destruction and deaths near the northern coast of Akita and elsewhere in Japan and Korea were caused by the tsunami.

Date and Time of Occurrence - 26 May 1983; 12:00

Epicenter - 40.46 N 139.10 E NEAR WEST COAST OF HONSHU, JAPAN.

Magnitude - The magnitude was invariably given as Ms 7.7 (BRK), 7.7 (PAS), 7.8 (PAL) and as 7.9 (Mw)

Quake Felt - The earthquake ground motions were strongly felt throughout northern and central island of Honshu and in Hokkaido.

Earthquake Focal Mechanism - The focal mechanism of this earthquake was moderately well controlled and corresponded to reverse faulting.

Seismicity of the Region - The seismicity of Northern Japan is the result of a double seismic zone (DSZ), and compressional deep trench and outer rise events and by the magmatic effects of plumes or superplumes which, originally, may have hydrated the subducting oceanic lithosphere. Usually, shallow normal faulting occurs in the trench-outer rise region. Earthquakes in the Sea of Japan occur less frequently.

Damages and Death Toll from Earthquake and Tsunami - The earthquake and tsunami waves caused extensive damage to dwellings, roads, and vessels along the Japan Sea coast from southern Hokkaido to the Niigata area, Honshu. At least 104 people were killed and 325 others were injured. 5100 houses were damaged. Many of the casualties and much of the damage occurred on the Oga Peninsula of the Akita Prefecture. Most of the earthquake damage to buildings resulted from ground liquefaction. Tsunami damage occurred as far away as the Yamaguchi Prefecture in southwestern Honshu, along the Japan Sea coast of Russia ( then USSR), and along the eastern and southern coasts of South Korea, where three people were killed.

Tectonic Setting of the Northern Japan/Kuril Island Region

Tectonic Setting - The overall tectonics of northeast Asia are very complicated. Whether the Sea of Okhotsk and the northern Japanese islands are part of the North American plate or of a separate Okhotsk plate has not been determined. On the Pacific Ocean side, earthquake slip vectors along the Kuril and Japan trenches are consistent with either a Pacific-North America or a Pacific-Okhotsk plate motion. We will assume that the Pacific-North America plate motion is better supported.

The Kuril island arc is located between the Kamchatka Peninsula and the Japanese island of Hokkaido. The Kuril Trench has been formed by the subduction of the Pacific plate under the North American plate. It extends from the offshore central area of Kamchatka to Hokkaido.

The plate tectonics of the Southern Kuril islands-Northern Hokkaido region are quite complex and very different than those along the southern portion of the Japanese Trench. The South Kuril Islands are part of the Kuril arc in the Okhotsk plate which has been colliding westward against the Northeast Japan arc, along the Hidaka Collision Zone (HCZ), where new continental crust is created by active arc-arc collision.

Deep seismic reflection studies (Ito, Kazuka @Abe, 2001) show the lower crust of the Kuril arc to be delaminated at a depth of about 23 km. These studies indicate that the upper half (above 23 km) - consisting of the earth's upper crust and the upper portion of lower crust of the Kuril arc - is thrusting over the Northeast Japan arc along the Hidaka Main Thrust (HMT). However, the lower half (below 23 km) - consisting of the lower portion of lower crust and upper mantle material - is descending downward.

Ocean bottom morphology of Kamchatka, the Kuril Island Trench, Sakhalin Island, and the Sea of Okhotsk.

As a result of such kinematic processes, the wedge of the Northeast Japan arc is intruded into the delaminated Kuril arc, as the Pacific plate is subducting northward beneath both of the above mentioned structures, thus continuing the arc-arc collision (and continental crust production). The complex, seismo- tectonic kinematic process of this region has been named "Delamination-wedge-subduction system" - which may apply also to other areas where active arc-arc collision and concurrent subduction take place.

 

Accordingly Hokkaido - Japan's northernmost island - extends northeast into Kuril Islands and is composed of multiple compressed island arcs. The northern half of Honshu (north of Tokyo), which is Japan's main island, represents a typical mature island arc, with the Pacific plate subducting below the North American plate, while the southern half of the island represents also a typical mature island arc, as the Philippine Sea plate subducts below the Eurasian plate.

On the western side, the Sea of Japan is a complex basin between Japan and the Korea/Okhotsk Sea Basin. It represents another subplate with apparent rotational movement as it interacts against the Okhotsk plate, along the inland sea boundary of the Hidaka Collision Zone (HCZ). Sakhalin island , north of Hokkaido, which separates the Sea of Japan from the Sea of Okhotsk, is probably the result of transpressional tectonics along the North America-Eurasia boundary. The 1983 earthquake and tsunami in the Sea of Japan occured south of the boundary of these interacting subplates. This a seismic region that has generated tsunamis in the past, which have caused considerable damage along the Japanese, Russian and Korean coasts.

The Tsunami of 26 May 1983 in the Sea of Japan / East Sea

The Tsunami

The earthquake of 26 May 1983 generated a destructive tsunami in the Sea of Japan. The first of the destructive tsunami waves took seven minutes after the earthquake to strike the coast of the Akita Prefecture in the north-east part of the Honshu Island, in northern Japan. Maximum waves reached 14 m along the coast of Akita. Also, the eastern coast of Korea was struck by destructive waves.

There was no sufficient time to issue a local warning. A warning was issued about 13- 15 minutes after the earthquake. It was too late. One hundred four persons died in Japan and three more in Korea. There was extensive destruction of houses, ships and port facilities.

Tsunami Generating Area and Tsunami Travel Times in the Sea of Japan and around the Japanese Islands ( in minutes) .

Subsequent surveys of the affected region along the western coast of Japan , sponsored by Japan's National Research Center for Disaster Prevention, documented the effects and runup heights of the tsunami waves. The results of these surveys are summarized here.

Tsunami Wave Heights - Estimated tsunami heights were 14 meters at Minehama, Honshu, 2-6 meters along southern Hokkaido and northern Honshu, up to 8 meters along the coast of Russia (USSR at the time), and ranged between 2-7.5 meters along the coast of South Korea.

Damages and Death Toll from the Tsunami - Many of the casualties and much of the tsunami damage occurred on the Oga Peninsula of the Akita Prefecture. Tsunami damage occurred as far away as the Yamaguchi Prefecture in southwestern Honshu, along the Japan Sea coast of Russia ( then USSR), and along the eastern and southern coasts of South Korea, where three people were killed.

The tsunami comletely destroyed Oga Peninsula in Japan

The Tsunami in the Akita Prefecture of Japan - The tsunami reached more than 11 m (max 14 m.) along the Akita Prefecture in the northern coast of Japan.There was extensive destruction of houses,buildins, ships and port facilities. It caused a number of fatalities. A total of 104 persons died. The tsunami destroyed 700 boats and 59 houses for a total of $800 million in property damage (1983 dollars).

The Effects of the Tsunami in Southern Korea - It took approximately 90 minutes for the first tsunami wave to travel across the Japan Sea and strike the east coast of the Korean Peninsula. This was the first tsunami to inflict heavy damage on the eastern coast of Korea since the 1741 Oshima-oshima tsunami. According to observations, the wave reached a height of 5 meters on Ullung Is.. Samchuk port, Geunduk, Yongwha beach and Yongwha port were also affected. Damage was particularly significant at the Imwon port, where tsunami runup height was about 3.6 m. On a coastal road close to Imwon the tsunami runup reached 5.1 m. Maximum runup of 7.5 m occurred at the upper part of the town along the river. Three persons were killed and twenty houses were damaged or destroyed.

At Wondok Town and Kangwon-do, a maximum tsunami height of 3.6-4.0m was recorded. Fishing boats were carried into the residential area, and a gas oil tank holding 130,000 litters was carried by about 10 meter. One person was killed at Tonghae City. The amount of damage in the Republic of Korea was estimated to be about 400 million won (about $500,000 - 1983 US dollars).
 
Tide gauge recordings in South Korea showed the initial sea level movement to be rise at Pusan. Ulsan, Mukho (Tonghae City), Sokch'o, and Chodong (Ullung Island). However, at P'ohang port the tide gauge record indicates an initial drop in sea level.

Lessons Learned - Even in a country like Japan where there is considerable awareness of the tsunami danger, it is very difficult to issue local warnings when the earthquake source is so close to the coast. However, as a result of this tsunami, there was an increased effort for public education. Japan introduced a new regional system which offers a shorter lead time for tsunami warnings.

 

Historical Tsunamis in the Sea of Japan / East Sea
Historical tsunamis generated by earthquakes along the possible boundary of the Eurasian and the North American plates, in the Sea of Japan, have been responsible for a great deal of destruction along the coastal areas of Japan, Russia and Korea. A review of archival material in Japan and Korea will undboubtedly reveal the occurrence of many historical tsunamis in the Sea of Japan - perhaps as many as 6-8 events spaced apart in time and location. Most noteworthy of the known historical events are the following.

Recent reports in the literature, quoting records of the Choson Dynasty, indicate that the Kampo earthquake of 1741 (estimated magnitude M = 7.5), off the southwestern coast of Hokkaido, in the Sea of Japan, generated a destructive tsunami that was responsible for the death of about 1,500 people and that the waves affected the entire coast of Kangwondo, destroying houses and boats.


More recently, the earthquake of 1949 (M = 7.5) - known as the Kamuizaki-Oki Earthquake - and the Tsunami it generated were destructive. In the east coast of the Korean Peninsula, the tsunami waves ranged up to 2.0m at Uljin, Kyongsang-Pukdo, and the island of Ullung.

Photos of tsunami effects, inundation and destruction along the Akita Prefecture of Japan

Note the movement of the heavy, concrete tetrapods which had been placed for protection along the shore

REFERENCES AND FURTHER READING

(Tetsuzo Seno and many other Japanese and Korean scientists have studied extensively the tectonic interactions along the Japanese arc. The following are selected references for further reading on the kinematics of this complex tectonic area of the world, which historically has produced numerous destructive tsunamis).

 

Aida, I. (1984), A source models of the 1983 Nihonkai-earthquake tsunami, Proceeding of 3rd UJNR(UnitedStates-Japan Cooperative Program in Natural Resources) Tsunami Workshop, pp. 57-76.

Nakamura, K., V. Renard, J. Angelier, J. Azema, J. Bourgois, C. Deplus, K. Fujioka, Y. Hamano, P. Huchon, H. Kinoshita, P. Labaume, Y. Ogawa, T. Seno, A. Takeuchi, M. Tanahashi, A. Uchiyama, and J. L. Vigneresse. Oblique and near collision subduction, Sagami and Suruga troughs -Preliminary results of French-Japanese 1984 KAIKO cruise, leg 2 Earth Planet. Sci. Lett. 83 229-242 1987


Nakasa, Y., and T. Seno.
Compensation mechanism of the Yamato Basin, Japan Sea J. Phys. Earth 42 187-195 1994


NIDP (1999),
Study on tsunami hazards mitigations along the Korean eastern coast(I), Report of NIDP (National Institute for Disaster Prevention), 192 pp.


Ogawa, Y., T. Seno, H. Akiyoshi, H. Tokuyama, K. Fujioka, and H. Taniguchi.
Structure and development of the Sagami Trough and off-Boso triple junction Tectonophysics 160 135-150, 1989


Kawakatsu, H., and T. Seno.
Triple seismic zone and the regional variation of seismicity along the northern Honshu arc. J. Geophys. Res. 88 4215-4230 1983

Renard, V., Nakamura, K., J. Angelier, J. Azema, J. Bourgois, C. Deplus, K. Fujioka, Y. Hamano, P. Huchon, H. Kinoshita, P. Labaume, Y. Ogawa, T. Seno, A. Takeuchi, M. Tanahashi, A. Uchiyama, and J. L. Vigneresse.
Trench triple junction off central Japan - Preliminary results of French-Japanese 1984 KAIKO cruise, leg 2 Earth Planet. Sci. Letters 87 243-256 1987

Seno, T. and D. G. Gonzalez. Faulting caused by earthquakes beneath the outer slope of the Japan Trench. J. Phys. Earth 35 381-407 1987

Seno, T.
Is northern Honshu a microplate? Tectonophysics 115 177-196 1985

Seno, T.
Syntheses of the regional stress fields of the Japanese islands The Island Arc 8 66-79 1999


Seno, T., and Y. Yamanaka.
Arc stresses determined by slabs: Implications for mechanisms of back-arc spreading Geopys. Res. Lett. 25 3227-3230 1998

Seno, T., and Y. Yamanaka.
Double seismic zones, compressional deep trench - outer rise events and superplumes in Subduction Top to Bottom, edited by G. E. Bebout, D. W. Scholl, S. H. Kirby, and J. P. Platt Geophys. Monogr. 96 347-355 1996


Seno, T., T. Sakurai, and S. Stein.
Can the Okhotsk plate be discriminated from the North American plate? J. Geophys. Res. 101 11305-11315 1996


Seno, T.
Intraplate sesmicity in Tohoku and Hokkaido and large interplate earthquakes: A possibility of a large interplate earthquake off the southern Sanriku coast, northern Japan J. Phys. Earth 27 21-51 1979

Seno, T. Pattern of intraplate seismicity in southwest Japan before and after great interplate earthquakes Tectonophysics 57 267-283 1979

Seno, T., Shimazaki, K., Somerville, P., Sudo, K., and T. Eguchi. Rupture process of the Miyagi-Oki, Japan, earthquake of June 12, 1978 Phys. Earth Planet. Inter. 23 39-61, 1980

Seno, T., and B. Pongsawat. A triple-planed structure of seismicity and earthquake mechanisms at the subduction zone off Miyagi Prefecture, northern Honshu, Japan Earth Planet. Sci. Lett. 55 25-36, 1981

Seno, T., and G. C. Kroeger. A reexamination of earthquakes previously thought to have occurred within the slab between the trench axis and double seismic zone, northern Honshu J. Phys. Earth 31 195-216 1983


Seno, T., and T. Takano.
Seismotectonics at the trench-trench-trench triple junction off central Honshu Pure Appl. Geophys. 129 27-40, 1989

Seno, T., T. Sakurai, and S. Stein. Can the Okhotsk plate be discriminated from the North American plate? J. Geophys. Res. 101 11305-11315, 1996

Seno, T., and Y. Yamanaka. Double seismic zones, compressional deep trench - outer rise events and superplumes in Subduction Top to Bottom, edited by G. E. Bebout, D. W. Scholl, S. H. Kirby, and J. P. Platt Geophys. Monogr. 96 347-355, 1996

Seno, T. Earthquake Research Institute, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan The Island Arc, 8, 66-79, 1999


Watanabe, T., T. Koyaguchi, and T. Seno.
Tectonics stress controls on ascent and emplacement of magmas J. Volcanol. Geotherm. Res. 91 65-78, 1999

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