1987 Chiba earthquake

Earthquake near Tokyo, Japan

1987 Chiba earthquake千葉県沖地震

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UTC time| 1987-12-17 02:08:19
ISC event| 450774
USGS-ANSS| ComCat
Local date| December 17, 1987 (1987-12-17)
Local time| 11:08
Magnitude| 7.3 Me[1]
6.7 Mw[2]
Depth| 62.9 km (39.1 mi)
Epicenter| 35°22′19″N 140°31′08″E﻿ / ﻿35.372°N 140.519°E﻿ / 35.372; 140.519[3]
Type| Strike-slip
Max. intensity| JMA 5− [4]

VII (Very strong)
Casualties| 2 dead, 144 injured

The 1987 Chiba Prefecture offshore earthquake (Japanese: 1987 千葉県沖地震) occurred off the east coast of the Boso Peninsula in Chiba Prefecture at 11:08:01 JST on December 17, 1987.

## Tectonic setting[edit]

The crustal structure in the southern Kanto region is complex, involving boundaries between three tectonic plates. The Philippine Sea Plate is subducting beneath the Okhotsk Plate along the line of the Sagami Trough and beneath the Eurasian Plate along the line of the Nankai Trough. Further to the east, the Pacific Plate is subducting beneath the Okhotsk and Philippine Sea plates along the line of the Japan Trench.[3] A velocity analysis of the region beneath Kanto suggests that the wedge of oceanic mantle lithosphere of the Philippine Sea Plate in contact with the Pacific Plate is affected by serpentinization as shown by the anomalously low seismic velocity. The boundary between the serpentinized and unmetamorphosed parts of the mantle wedge is interpreted to be vertical and NNW–SSE trending.[5]

## Earthquake[edit]

The earthquake had a strike-slip focal mechanism, which with its depth, indicates that it was a result of faulting within the Philippine Sea Plate. The focal mechanism gives two possible fault planes, one west–east trending, dipping steeply to the south, and the other north–south trending, dipping steeply to the east. The distribution of aftershocks suggests a NNW–SSE trending rupture, consistent with the nearly north–south fault plane, indicating dextral (right-lateral) strike-slip faulting with a small component of reverse faulting.[3] The earthquake is interpreted to have ruptured part of the boundary between the two parts of the Philippine Sea Plate mantle wedge.[5]

## Damage[edit]

According to the materials of the Fire and Disaster Prevention Division of the Chiba Prefecture General Affairs Department, two deaths (one in Mobara and another in Ichihara), 26 serious injuries and 118 minor injuries were reported. 16 buildings collapsed, 102 were severely damaged, and 63,692 suffered minor damage. Three fires, power outages, and train service disruptions were also reported.[6][7] Liquefaction was observed on landfills and riverbanks. Even though most of the damage occurred in Chiba Prefecture, damage and landslides were also reported in Kanagawa Prefecture.[8][9][10]

## See also[edit]

* List of earthquakes in 1987
* List of earthquakes in Japan
* 2012 Chiba earthquake
* 2021 Chiba earthquake

## References[edit]

1. ^ "M 6.7 - 10 km SW of Mobara, Japan - Technical Summary". earthquake.usgs.gov.
2. ^ "M 6.7 - 10 km SW of Mobara, Japan". earthquake.usgs.gov.
3. ^ a b c Okada, Y.; Kasahara, K. (1990). "Earthquake of 1987, off Chiba, central Japan and possible triggering of eastern Tokyo earthquake of 1988". Tectonophysics. 172 (3–4): 351–364. Bibcode:1990Tectp.172..351O. doi:10.1016/0040-1951(90)90041-6.
4. ^ "震度データベース検索". 気象庁. Retrieved 2022-04-11.
5. ^ a b Nakajima, J.; Hasegawa, A. (2010). "Cause of M ~ 7 intraslab earthquakes beneath the Tokyo metropolitan area, Japan: Possible evidence for a vertical tear at the easternmost portion of the Philippine Sea slab". Journal of Geophysical Research: Solid Earth. 115 (B4). Bibcode:2010JGRB..115.4301N. doi:10.1029/2009JB006863.
6. ^ "1987年千葉県東方沖地における災害情報の伝達と市町村・住民の対応] 東京大学社会情報研究所廣井研究室" [1987 Transmission of disaster information off the east coast of Chiba Prefecture and response of municipalities and residents] (PDF). Hiroi Laboratory, Institute of Social Information, University of Tokyo. Archived from the original (PDF) on 2016-03-05. Retrieved 2022-04-11.
7. ^ 千葉県東方沖地震による山地災害とその対応 -その後 地すべり Vol.26 (1989-1990) No.1 P.41-43, doi:10.3313/jls1964.26.41
8. ^ 久保 徹：千葉県東方沖地震に伴う三浦半島の被害状況 地すべり Vol.24 (1987-1988) No.4 P.39-40, doi:10.3313/jls1964.24.4_39
9. ^ Butts, David (December 17, 1987). "Earthquake in Japan kills two, injures 53". United Press International. Retrieved April 12, 2022.
10. ^ "千葉県東方沖地震" [Chiba Prefecture East Offshore Earthquake]. typhoon.yahoo.co.jp (in Japanese). Retrieved April 12, 2022.

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Earthquakes in Japan

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* 1854 Nankai
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* 1872 Hamada
* 1889 Kumamoto
* 1891 Mino–Owari
* 1894 Tokyo
* 1894 Shōnai
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20th century|

* 1911 Kikai Island
* 1914 Senboku
* 1923 Great Kantō
* 1925 North Tajima
* 1927 North Tango
* 1930 North Izu
* 1933 Sanriku
* 1936 Miyagi
* 1939 Oga
* 1940 Shakotan
* 1941 Hyūga-nada
* 1943 Tottori
* 1944 Tōnankai
* 1945 Mikawa
* 1946 Nankai
* 1948 Fukui
* 1952 Tokachi
* 1961 North Mino
* 1963 Kuril Islands
* 1964 Niigata
* 1968 Ebino
* 1968 Hyūga-nada
* 1968 Tokachi
* 1973 Nemuro Peninsula
* 1974 Izu Peninsula
* 1978 Izu Ōshima
* 1978 Miyagi
* 1982 Urakawa
* 1983 Sea of Japan
* 1984 Nagano
* 1993 Kushiro
* 1993 Okushiri
* 1994 offshore Sanriku
* 1995 Hanshin
* 2000 Tottori

21st century|

* 2001 Geiyo
* 2003 Miyagi
* 2003 Tokachi
* 2004 Chūetsu
* 2005 Fukuoka
* 2005 Miyagi
* 2006 Kuril Islands
* 2007 Chūetsu
* 2007 Kuril Islands
* 2007 Noto
* 2008 Iwate–Miyagi
* 2008 Iwate
* 2009 Shizuoka
* 2011 Tōhoku
* 2011 Nagano
* 2011 Shizuoka
* 2011 Miyagi
* 2011 Fukushima
* 2012 Chiba
* 2012 Sanriku
* 2014 Nagano
* 2015 Ogasawara
* 2016 Kumamoto
* 2016 Tottori
* 2016 Fukushima
* 2018 Osaka
* 2018 Hokkaido Eastern Iburi
* 2019 Yamagata
* 2021 Fukushima
* 2021 Miyagi
* 2021 Chiba
* 2022 Fukushima
* 2023 Ishikawa
* 2024 Noto

Related articles|

* Tōkai earthquakes
* Nankai megathrust earthquakes
* Kantō earthquakes
* South Kantō earthquakes
* Matsushiro earthquake swarm
* Noto earthquake swarm

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← Earthquakes in 1987 →

* Edgecumbe (6.5, Mar 2)
* Ecuador (7.1, Mar 6) † ‡
* Whittier Narrows (5.9, Oct 1)
* Santiago de Chuco (5.6, Oct 2)
* Imperial County (6.2, 6.6, Nov 23, 24)

† indicates earthquake resulting in at least 30 deaths
‡ indicates the deadliest earthquake of the year
*[Max.]: Maximum
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