Advancement of the capacitive resistivity method to estimate ice content in permafrost.

估算永久冻土中冰含量的电容电阻率方法的进展。

基本信息

批准号：
213214736
负责人：
Professor Dr. Andreas Hördt
金额：
--
依托单位：
Institut für Geophysik und Extraterrestrische Physik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/213214736?language=en
关键词：
Advancement capacitive resistivity method estimate

项目摘要

Permafrost ist permanently frozen ground that exists predominantly in polar regions and high-altitude mountains. The global abundance of permafrost is essential for ecology, infrastructure and the carbon inventory of the earth. In the context of global warming, the mapping and observation of permafrost occurence becomes increasingly important; a task where geophysics can make substantial contributions. Refraction seismics and DC resistivity methods are most frequently used, however, they can be logistically difficult to apply in rough terrain. In this project, we investigate the feasibility of capacitive resistivity for permafrost research. Instead of metal sticks, electrode sheets are being used, which may inject a high-frequency alternating current without direct contact to the ground. The high-frequency alternating current offers the opportunity to determine electrical permittivity, which constitutes important complementary information in addition to the electrical conductivity. In the frequency range between 10 Hz and 100 kHz, the permittivity of water ice displays a characteristic frequency dependence, which shall be exploited to estimate the ice content in frozen rocks. So far, we developed and tested suitable equipment in cooperation with the manufacturer. With an appropriate theoretical description of the measured impedance, we demonstrated at several locations that the typical frequency spectrum of permittivity may be measured under field conditions. Here, we propose to continue the project by applying the method to several specific problems. At three locations in Switzerland, which are frequently investigated by other working groups and where extensive a priori information is available, we will characterize the inner structure of the permafrost bodies and estimate the ice content. In another region located in Siberia, we will, in addition to the estimation of the ice content, delineate the boundary between the frozen and unfrozen ground and map its lateral variation. The application requires further methodological requirements. In our previous experiments, the penetration depth was limited to a few meters; we intend to push the limits as far as possible. In particular, we will investigatie and avoid distortion by electromagnetic coupling effects, which become increasingly important for larger electrode spacing. We also will adapt inversion and interpretation methods to the large bandwidth and the large phase phase shift of the impedance compared to more conventional techniques.

永久性冻土永久冷冻的地面，主要存在于极地和高海拔山脉中。永久冻土的全球丰度对于生态学，基础设施和地球的碳库存至关重要。在全球变暖的背景下，对永久冻土发生的映射和观察变得越来越重要。地球物理学可以做出重大贡献的任务。折射地震学和直流电阻率方法是最常使用的，但是，它们在崎terrain中可能很难应用。在该项目中，我们研究了电容电阻率对多年冻土研究的可行性。使用电极板而不是金属棒，它可能会注入高频交替的电流，而无需直接接触地面。高频交替电流提供了确定电介电常数的机会，除电导率外，该电流构成了重要的互补信息。在10 Hz至100 kHz之间的频率范围内，水冰的介电性显示出特征性的频率依赖性，应利用该频率依赖性以估算冷冻岩石中的冰含量。到目前为止，我们与制造商合作开发并测试了合适的设备。通过对测量阻抗的适当理论描述，我们在几个位置证明了典型的介电常数频谱可以在田间条件下测量。在这里，我们建议通过将方法应用于几个特定问题来继续该项目。在瑞士的三个地点，这些地点经常由其他工作组进行研究，并且在可获得广泛的先验信息的情况下，我们将表征多年冻土体的内部结构并估算冰含量。在西伯利亚的另一个地区，除了对冰含量的估计外，我们还将描绘冰冻和未覆盖的地面之间的边界并绘制其横向变化。该应用需要进一步的方法论要求。在我们以前的实验中，穿透深度仅限于几米。我们打算尽可能地推动极限。特别是，我们将通过电磁耦合效应进行研究并避免失真，这对于较大的电极间距变得越来越重要。与更常规的技术相比，我们还将适应大型带宽和阻抗的大相位移位。