The Matsushiro earthquake swarm (Japanese: 松代群発地震[1]) was an earthquake swarm that occurred near Matsushiro, a suburb of Nagano, to the northwest of Tokyo in 1965. The event is one of the best ever documented earthquake swarms.
(August 1965 ~ May 1967)
Overview
editThe Matsushiro swarm lasted from 1965 to 1967 and generated about 1 million earthquakes.[2] The total sum of energy from all the tremors was approximately equivalent to an M6.4 earthquake.[3][4] This swarm had the peculiarity to be sited just under a seismological observatory installed in 1947 in a decommissioned military tunnel. It began in August 1965 with three earthquakes too weak to be felt, but three months later, a hundred earthquakes could be felt daily. On 17 April 1966, the observatory recorded 6,780 earthquakes, with 585 of them having a magnitude large enough to be felt, which meant that one earthquake could be felt every 2 minutes 30 seconds on average.[5] The phenomenon was clearly identified as linked to a magma uplift, perhaps initiated by the 1964 Niigata earthquake which happened one year before.[6]
References
edit- ^ 日本国語大辞典,デジタル大辞泉,世界大百科事典内言及, 日本大百科全書(ニッポニカ),精選版. "松代群発地震とは". コトバンク (in Japanese). Retrieved 2021-05-26.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ "松代群発地震（1965年8月3日） ｜ 災害カレンダー". Yahoo!天気・災害 (in Japanese). Retrieved 2021-05-26.
- ^ "松代群発地震_松代地震観測所". www.data.jma.go.jp. Retrieved 2021-05-26.
- ^ 国立天文台 『理科年表 令和3年』 丸善 P.801 ISBN 978-4-621-30560-7
- ^ "Matsushiro earthquake swarm". www.data.jma.go.jp. Retrieved 2017-10-31.
- ^ Mogi, Kiyoo (1989). "The mechanics of the occurrence of the Matsushiro earthquake swarm in central Japan and its relation to the 1964 Niigata earthquake". Tectonophysics. 159 (1–2): 109–119. Bibcode:1989Tectp.159..109M. doi:10.1016/0040-1951(89)90173-X.
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