Sakurajima volcano, open conduit, gravity change, crustal movements, response function
その他のタイトル
Diagnosis of Conduit State of Sakurajima Volcano Using Continuous Records on Gravity and Crustal Movements (Special Issue: “Possible Effect of Mega Earthquake on Long-term Volcanic Activity” Part 2)
Sakurajima is one of the most active volcanoes in the world; 500 to 1,000 explosions have occurred every year since 2009. In particular, significant seismicity (>800 volcano-tectonic earthquakes in 15 hours) and crustal deformations (>10 cm displacement) were observed on Aug. 15, 2015, followed by an unusually long quiescent period since October 2015. The event is attributed to a dyke intrusion (tensile dislocation accompanied by magma injection) beneath the volcano. We compare gravity change Δg(t) with strain and tilt records ε(t) and find two remarkable aspects: (i) ratio |Δg(t)/ ε(t)| during dyke intrusion (Aug. 15, 2015) is 20 times smaller than that during the other explosion period; and, (ii) time lag between Δg(t) and ε(t) is negligibly small during dyke intrusion, while it is Δg(t) during the other period, exhibiting a significant time lag (～1 day) to ε(t). These characteristics are explained well from the viewpoint of whether the conduit is open to the free surface or is blocked.
雑誌名
東京大学地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
92
号
2-4
ページ
91 - 99
発行年
2017
ISSN
00408972
書誌レコードID
AN00162258
著者版フラグ
publisher
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
重力と地殻変動連続観測に基づく桜島火山の火道状態の診断 (特集:「巨大地震と火山活動」Part 2)
IHO922405.pdf
(2.28MB)
