2:45 PM - 3:00 PM
[SVC47-05] Gravity vs Strain/Tilt Changes at Sakurajima Volcano from the Dyke Intrusion Event in August 2015 through Resumption of Frequent Explosions in February 2016
Keywords:Gravity, Sakurajima, Magma Head, Crustal Deformation, Open Conduit, Vulcanian Eruption
We compared gravity g(t) with strain or tilt record e(t) on Sakurajima volcano. Two aspects are noteworthy to point out. That is,
(1) The ratio | g(t) / e(t) | during the dyke intrusion (Aug. 15, 2015) is 100 times smaller than that during the other explosion period.
(2) Time lag between g(t) and e(t) is negligibly small during the dyke intrusion (Aug. 15, 2015) while g(t) during the other period shows significant time lag (~1 day) to e(t).
These characteristics are well explained in terms of the conduit status (open/closed). When the conduit is closed as in the case of the dyke intrusion event, both strain/tilt and gravity are principally governed by instantaneous elastic deformation, which implies absence of time lag. On the other hand, when the conduit is open as in the explosion period other than the dyke intrusion event, inflation/deflation of magma chamber does not cause effective elastic deformation, which means larger |g(t) / e(t) | compared to the case of closed conduit and significant time lag of g(t) to e(t) because magma migration in a conduit requires certain amount of time.