Kinematic analysis of vertical collapse on volcanoes using experimental models time series
Kinematic analysis of vertical collapse on volcanoes using experimental models time series
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使用实验模型时间序列对火山垂直塌陷进行运动分析
DOI：
10.1029/2012jb009229
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发表时间：
2012
影响因子：
--
通讯作者：
F. Corbi
中科院分区：
文献类型：
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作者：
J. Ruch;V. Acocella;N. Geshi;Adriano Nobile;F. Corbi
火山经常与垂直塌陷联系在一起，这是由于更深的岩浆撤退。火山口是最显著的垂直塌陷类型，在火山的顶部。只在Miyakejima（日本，2000年），Dolomieu（留尼旺岛，2007年）和Fernandina（加拉帕戈斯群岛，1968年）观察和监测过火山口崩塌，这突出了我们对其运动学行为的有限了解。在这里，我们使用实验模型来研究火山口和垂直崩塌的运动学演化。利用粒子图像测速（PIV）技术提取速度场和应变场，生成时间序列。恒定沉降速度下的垂直塌陷实验表现出三种主要的运动学行为：(1)连续塌陷，其速度与源沉降速度相近；(2)渐进式崩塌，沿预先存在的环形结构具有幕式（逐步）加速；(3)突发性塌陷，由空腔向上移动引起，仅适用于T/D bbb2 （T和D分别为岩浆房的深度和宽度），不存在环状构造。相对于震源的恒定沉降速度，陷落柱内的速度可增加4个数量级。与自然界的对比表明：(1)与监测到的崩塌破火山口有着密切的运动学相似性，解释了它们在环形构造发育后的渐进式沉降；(2)突发性坑坑的形成是由于深部岩浆的移除和环形构造的缺失导致的空洞向上扩展所致；(3)各类型垂直塌陷的形成机制和运动行为、T/D和环状构造的存在与否具有一致的作用。
[1] Volcanoes are often associated with vertical collapse, due to deeper magma withdrawal. Calderas are the most notable type of vertical collapse, on the summit of volcanoes. Caldera collapse has been observed and monitored only at Miyakejima (Japan; 2000), Dolomieu (Reunion; 2007) and Fernandina (Galapagos; 1968), highlighting our limited knowledge on its kinematic behavior. Here we use experimental models to investigate the kinematic evolution of calderas and vertical collapses in general. We extract velocity and strain fields using the Particle Image Velocimetry (PIV) technique, generating time series. Experimental vertical collapses undergoing constant subsidence velocity show three main kinematic behaviors: (1) continuous collapse, whose velocity is similar to the source subsidence velocity; (2) incremental collapse, with episodic (stepwise) accelerations along pre-existing ring structures; (3) sudden collapse, resulting from the upward migration of a cavity, only for T/D > 2 (T and D are the depth and width of the magma chamber, respectively) and without ring structures. The velocity in the collapsing column may increase up to four orders of magnitude with regard to the constant subsidence velocity of the source. Comparison to nature suggests that: (1) there are close kinematic similarities with monitored collapse calderas, explaining their incremental subsidence after the development of ring structures; (2) sudden pit crater formation is induced by the upward propagation of cavities, due to magma removal at depth and in absence of ring structures; (3) all these types of vertical collapses have a consistent mechanism of formation and kinematic behavior, function of T/D and the presence/absence of ring structures.