Rapid changes in magma storage beneath the Klyuchevskoy group of volcanoes inferred from time-dependent seismic tomography

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• 作者：Ivan Koulakov ; Evgeniy I. Gordeev ; Nikolay L. Dobretsov ; Valery A. Vernikovsky ; Sergey Senyukov ; Andrey Jakovlev ; Kayrly Jaxybulatov
• 关键词：Seismic tomography ; Kluchevskoy volcano ; Magma sources ; Kamchatka
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：2013
• 出版时间：1 August, 2013
• 年：2013
• 卷：263
• 期：Complete
• 页码：75-91
• 全文大小：9614 K

文摘

We present the results of time-dependent local earthquake tomography for the Kluchevskoy group of volcanoes in Kamchatka, Russia. We consider the time period from 1999 to 2009, which covers several stages of activity of Kluchevskoy and Bezymianny volcanoes. The results are supported by synthetic tests that recover a common 3D model based on data corresponding to different time windows. Throughout the period, we observe a robust feature below 25 km depth with anomalously high V_p/V_s values (up to 2.2). We interpret this feature as a channel bringing deep mantle materials with high fluid and melt content to the bottom of the crust. This mantle channel directly or indirectly determines the activity of all volcanoes of the Kluchevskoy group. In the crust, we model complex structure that varies over time. During the pre-eruptive period, we detected two levels of potential magma storage: one in the middle crust at 10-12 km depth and one close to the surface just below Kluchevskoy volcano. In 2005, a year of powerful eruptions of Kluchevskoy and Besymiyanny volcanoes, we observe a general increase in V_p/V_s throughout the crust. In the relaxation period following the eruption, the V_p/V_s values are generally low, and no strong anomalous zones in the crust are observed. We propose that very rapid variations in V_p/V_s are most likely due to abrupt changes in the stress and deformation states, which cause fracturing and the active transport of fluids. These fluids drive more fracturing in a positive feedback system that ultimately leads to eruption. We envision the magma reservoirs beneath the Kluchevskoy group as sponge-structured volumes that may quickly change the content of the molten phases as fluids pulse rapidly through the system.