Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July–August 2008
Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July–August 2008
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DOI：
10.1029/2009jb006970
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发表时间：
2010-05
影响因子：
--
通讯作者：
Zhong Lu;D. Dzurisin
中科院分区：
文献类型：
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作者：
Zhong Lu;D. Dzurisin
[1]阿拉斯加奥克莫克火山口底锥体D附近的一次火山喷发于2008年7月12日开始，一直持续到2008年8月下旬。在这次喷发之前，位于火山口中心下方的岩浆库和海平面以下3公里处的∼岩浆库膨胀，这是在1997年奥克莫克上次喷发后立即开始的。本文利用几颗雷达卫星的数据和先进的干涉合成孔径雷达(InSAR)技术生成了一套2008年的强迫变形图。喷发期间发生的大部分地表变形是由位于火山口中心下方的莫吉型震源和2-3公里的BSL引起的，即基本上与喷发前膨胀的震源相同。在喷发期间，储集层以随时间呈指数下降的速度下降，1/e时间常数为∼13天。我们设想一个由相互连接的裂隙和熔体组成的海绵状网络，这些裂隙和熔体共同构成奥克莫克火山口下复杂的岩浆储存带。在喷发过程中，储集层的泄气速度可以由储集层和地表之间不断减小的压力差来控制。一种类似的机制可能解释了储集层膨胀随着喷发的临近而放缓的趋势，直到深部岩浆产生区和储集层之间的压力差足够大，足以沿着火山口环-裂缝系统驱动入侵或喷发。
[1] A hydrovolcanic eruption near Cone D on the floor of Okmok caldera, Alaska, began on 12 July 2008 and continued until late August 2008. The eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and ∼3 km below sea level (bsl), which began immediately after Okmok's previous eruption in 1997. In this paper we use data from several radar satellites and advanced interferometric synthetic aperture radar (InSAR) techniques to produce a suite of 2008 coeruption deformation maps. Most of the surface deformation that occurred during the eruption is explained by deflation of a Mogi-type source located beneath the center of the caldera and 2–3 km bsl, i.e., essentially the same source that inflated prior to the eruption. During the eruption the reservoir deflated at a rate that decreased exponentially with time with a 1/e time constant of ∼13 days. We envision a sponge-like network of interconnected fractures and melt bodies that in aggregate constitute a complex magma storage zone beneath Okmok caldera. The rate at which the reservoir deflates during an eruption may be controlled by the diminishing pressure difference between the reservoir and surface. A similar mechanism might explain the tendency for reservoir inflation to slow as an eruption approaches until the pressure difference between a deep magma production zone and the reservoir is great enough to drive an intrusion or eruption along the caldera ring-fracture system.