Micro-tilt changes preceding summit explosions at Semeru volcano, Indonesia
Micro-tilt changes preceding summit explosions at Semeru volcano, Indonesia
复制标题
印度尼西亚塞梅鲁火山山顶爆炸前的微倾斜变化
DOI：
10.1186/bf03352688
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
M. A. Purbawinata
中科院分区：
文献类型：
--
作者：
K. Nishi;M. Hendrasto;I. Mulyana;Umar Rosadi;M. A. Purbawinata
安装在印度尼西亚Semeru火山山顶的双轴倾斜仪揭示了两种不同的变形模式，短期和长期。短期变化是与峰顶爆发无关的膨胀。两次爆炸之间的时间间隔从几分钟到几十分钟不等，观测到的最大地壳倾斜变化约为0.1-0.2 μrad。这种倾斜的变化被解释为反映了一个浅的加压源，就在活动的陨石坑下面。长期的倾斜变化显示在几天到几周的时间内，在2005年12月22日火山碎屑流发生之前的近2周时间内稳定膨胀。短期和长期的变化都局限于径向倾斜分量，指向活跃的陨石坑和管道。为了解释这两个倾斜的变化，我们提出了相对较浅的管道加压，虽然在更深的水平，在长期变形的情况下。其成因机制涉及气体出溶、微晶结晶和流变硬化，这导致上部管道中更大的流动阻力和动压力，从而导致观察到的建筑物倾斜。岩浆中的气体孔隙压力不断增加，直到达到触发爆炸破碎所需的阈值。
A two-axis tiltmeter installed at the summit of Semeru volcano, Indonesia, reveals two different modes of deformation, short-term and longer-term. The short-term variations are inflations precursory to the occurrence of summit explosions. The time intervals between the explosions range from several minutes to several tens of minutes, and the maximum precursory tilt change observed is about 0.1–0.2 μrad. This change in tilt is interpreted to reflect a shallow pressurization source, just beneath the active crater. The longer-term tilt changes are displayed over a period of several days to weeks, and a steady inflation during a period of nearly 2 weeks preceded the occurrence of pyroclastic flows on December 22, 2005. Both short-term and longer-term changes are confined to the radial tilt component, pointing toward the active crater and conduit. To explain both of these tilt changes we propose relatively shallow conduit pressurization, although at somewhat deeper levels in the case of longer-term deformation. The causative mechanisms involve gas exsolution, microlite crystallization, and rheological stiffening, which results in greater flow resistance and dynamic pressure in the upper conduit, thus causing the edifice tilts observed. The gas pore pressure in the magma builds until the threshold required to trigger explosive fragmentation is reached.