Temperature‐calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps)
Temperature‐calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps)
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DOI：
10.1029/2008jf001209
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发表时间：
2010-06
影响因子：
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通讯作者：
M. Krautblatter;Sarah Verleysdonk;A. Flores-Orozco;A. Kemna
中科院分区：
文献类型：
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作者：
M. Krautblatter;Sarah Verleysdonk;A. Flores-Orozco;A. Kemna
[1]多年冻土岩墙内部岩石和冰的温度变化对冻土岩墙的稳定性有着重要的影响。楚格峰的永久冻土岩石在3.7 ka B. P.发生了0.3-0.4 km 3的落石，其沉积物现在居住着数千人。该峰（海拔2962米）107年的气候记录显示，1991-2007年气温急剧上升。本文应用电阻率层析成像技术（ERT）研究了冻土岩石的空间解冻和再冻结特性，首次提出了用冻结岩石温度标定ERT的方法。2007年2月和5月至10月期间，在楚格峰落石陡坎北侧进行了高分辨率ERT。一个平滑约束的反演与合并的数据误差模型，校准的基础上正常的倒数测量差异。楚格峰石灰岩的实验室分析表明，温度-电阻率关系呈双线性，除以0.5 ± 0.1°C和30 ± 3 kΩm的平衡凝固点，冻结温度-电阻率梯度增加了20倍（19.3 ± 2.1 kΩm/°C）。温度在-0.5 °C以下的岩石电阻率变化中占主导地位，而在这种情况下，地质参数则不那么重要。ERT显示了与温度数据相对应的岩石中冻结条件的衰退和复苏。最大电阻率变化的深度可达27米，与最大测量水流量在5月的裂缝。在这里，我们表明，实验室校准的ERT不仅可以识别冻结和未冻结的岩石，但提供定量信息冻结岩石温度相关的稳定性考虑。
[1] Changes of rock and ice temperature inside permafrost rock walls crucially affect their stability. Permafrost rocks at the Zugspitze were involved in a 0.3–0.4 km3 rockfall at 3.7 ka B.P. whose deposits are now inhabited by several thousands of people. A 107 year climate record at the summit (2962 m asl) shows a sharp temperature increase in 1991–2007. This article applies electrical resistivity tomography (ERT) to gain insight into spatial thaw and refreezing behavior of permafrost rocks and presents the first approach to calibrating ERT with frozen rock temperature. High-resolution ERT was conducted in the north face adjacent to the Zugspitze rockfall scarp in February and monthly from May to October 2007. A smoothness-constrained inversion is employed with an incorporated data error model, calibrated on the basis of normal reciprocal measurement discrepancy. Laboratory analysis of Zugspitze limestone indicates a bilinear temperature-resistivity relationship divided by a 0.5 ± 0.1°C and 30 ± 3 kΩm equilibrium freezing point and a twentyfold increase of the frozen temperature-resistivity gradient (19.3 ± 2.1 kΩm/°C). Temperature dominates resistivity changes in rock below −0.5°C, while in this case geological parameters are less important. ERT shows recession and readvance of frozen conditions in rock correspondingly to temperature data. Maximum resistivity changes in depths up to 27 m coincide with maximum measured water flow in fractures in May. Here we show that laboratory-calibrated ERT does not only identify frozen and unfrozen rock but provides quantitative information on frozen rock temperature relevant for stability considerations.