Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile.
Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile.
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DOI：
10.1007/s00445-011-0545-1
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发表时间：
2012
影响因子：
3.5
通讯作者：
Pavez, A.
中科院分区：
文献类型：
--
作者：
Whelley, Patrick L.;Jay, J.;Calder, E. S.;Pritchard, M. E.;Cassidy, N. J.;Alcaraz, S.;Pavez, A.
1993年智利拉斯卡火山喷发时的松散火山碎屑流沉积，随着时间的推移，越来越多地被深度穿透的裂缝网络切割。裂隙网络由垂直的分米宽的线性空洞组成，这些空洞形成了在矿床表面可见的伪多边形网格。在这项工作中，我们将浅层地球物理成像工具与遥感观测和矿床的直接野外测量相结合，以研究这些裂缝及其潜在的成因机制。根据探地雷达图像，观察到裂缝已扩展到10米深。此外，轨道雷达干涉测量表明，1993年至1996年期间，沉积物沉降高达1厘米/年−1，此后持续下沉的速度较慢。现场测量表明，在地表以下1米处，1993年的沉积物在侵位18年后仍比邻近的沉积物高5℃至15℃。根据观测到的下沉和估计的冷却速度，这些裂缝被推断为沉积后几个月到几年内脱氧、热收缩和沉积压实的综合结果。重要的环境因素，包括1995年和2007年的地区性地震，在断断续续的时刻加速沉降。裂缝形态的空间变化与地表坡度、岩相变化以及基岩岩性有关。据报道，类似的裂缝也出现在其他原始岩中，但通常只暴露在横截面上，通常被认为是由外力形成的。在这里，我们建议应谨慎地引用这样的解释，而变形，包括侵位后的沉降和在侵位后几个月到几年内松散堆积的富含火山灰的矿床的破裂，是火山碎屑物质沉降所固有的过程。本文的在线版本(doi：10.1007/s00445-0110545-1)包含补充材料，可供授权用户使用。
Unconsolidated pyroclastic flow deposits of the 1993 eruption of Lascar Volcano, Chile, have, with time, become increasingly dissected by a network of deeply penetrating fractures. The fracture network comprises orthogonal sets of decimeter-wide linear voids that form a pseudo-polygonal grid visible on the deposit surface. In this work, we combine shallow surface geophysical imaging tools with remote sensing observations and direct field measurements of the deposit to investigate these fractures and their underlying causal mechanisms. Based on ground penetrating radar images, the fractures are observed to have propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to 1 cm/year−1 occurred between 1993 and 1996 with continued subsidence occurring at a slower rate thereafter. In situ measurements show that 1 m below the surface, the 1993 deposits remain 5°C to 15°C hotter, 18 years after emplacement, than adjacent deposits. Based on the observed subsidence as well as estimated cooling rates, the fractures are inferred to be the combined result of deaeration, thermal contraction, and sedimentary compaction in the months to years following deposition. Significant environmental factors, including regional earthquakes in 1995 and 2007, accelerated settling at punctuated moments in time. The spatially variable fracture pattern relates to surface slope and lithofacies variations as well as substrate lithology. Similar fractures have been reported in other ignimbrites but are generally exposed only in cross section and are often attributed to formation by external forces. Here we suggest that such interpretations should be invoked with caution, and deformation including post-emplacement subsidence and fracturing of loosely packed ash-rich deposits in the months to years post-emplacement is a process inherent in the settling of pyroclastic material. The online version of this article (doi:10.1007/s00445-011-0545-1) contains supplementary material, which is available to authorized users.
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影响因子：
5.2
作者：
Druitt, TH;Bruni, G;Yates, JG
通讯作者：
Yates, JG
DOI：
10.1016/s0377-0273(97)00075-9
发表时间：
1998-04-01
影响因子：
2.9
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影响因子：
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作者：
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影响因子：
2
作者：
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通讯作者：
Carreno, F.