漠河盆地具有良好的天然气水合物成藏前景,了解盆地内冻土发育状况对评价水合物资源潜力和有利区优选十分重要。在东北漠河地区开展音频大地电磁测深(AMT)的剖面测量工作,目的之一是查明工区内冻土层埋深厚度以及空间分布。本文通过对东北漠河盆地北部冻土层电性特征的分析,依据冻土层的高阻特性进行了厚度识别和划分,勘探结果显示,漠河盆地北部冻土呈岛状分布,冻土分布特点为北厚南薄,西部薄,中东部厚,最大厚度为120 m,平均厚度40～80 m,反映了该区具有形成天然气水合物良好的冻土条件。

作为冻土区天然气水合物重要的成藏因素——盖层冻土的厚度,其勘探方法多样且各具特点。选择性价比较高的音频大地电磁测深(AMT)为探测技术,以青海木里地区为研究对象,通过多种典型模型的AMT正演模拟,并对正演响应进行一维自适应正则化反演与分析,结果表明一维正则化反演曲线取对数求导曲线(或称地层界面分层因子曲线)可较好地划分多年冻土层底板,并在木里地区划分多年冻土厚度中取得了较好的应用效果,为冻土区天然气水合物靶区预测提供良好的支撑作用。由过井DK9的两条十字剖面研究表明,井DK9附近的多年冻土厚度起伏变化不大,约在60～100 m之间变化,为天然气水合物的富集提供了良好的盖层条件。其中,垂直于断裂构造方向DK9-2剖面的多年冻土厚度变化较大,约为60～100 m;平行于断裂构造方向的DK9-1剖面的多年冻土厚度变化较小,为68～92 m。

在中低纬度多年冻土区多次实验分析如何改善音频大地电磁测深(AMT)高频段出现的"跳点"现象。根据测量结果认为天然电磁场信号、季节气候、采集时间、极距长短对高频段视电阻率数据下跳影响明显。提高野外测量数据质量,AMT高频段视电阻率测点具有真实圆滑连续性,对研究青藏高原冻土分布有重要指导意义。

根据祁连山永久冻土区区域地质背景、成矿条件和岩石物性特征,开展了CSAMT方法的探测研究。通过对CSAMT原始数据的分析解释,发现测区浅部0～100m深度段,呈现一似层状的高电阻率异常;在中深部存在纵向条带状低电阻率异常且电阻率呈现横向不连续变化。结合地质、钻孔资料得出浅部0～100m深度段的高电阻率异常为冻土层的反映,中深部呈现横向不连续的电阻率变化或纵向条带状低阻异常为断裂构造引起。因此认为CSAMT能够很好地分辨出天然气水合物形成、运移所需要的冻土盖层和断裂构造。

Global warming is likely to transform Siberian environments. Recent eco-hydrological evidence indicates that water and carbon cycles have been changing rapidly, with potentially serious effects on the Siberian flora and fauna. We have comprehensively analysed dendrochronological, hydrological, and meteorological data and satellite remote sensing data to track changes in vegetation and the water and carbon cycles in the Lena River Basin, eastern Siberia. The basin is largely covered with larch forest and receives little precipitation. However, from 2005 to 2008 the central part of the basin experienced an extraordinarily high level of precipitation in late summer and winter. This resulted in the degradation of permafrost, forest, and hydrological elements in the region. Dendrochronological data implied that this event was the only incidence of such conditions in the previous 150 years. Based on data collected before and after the event, we developed a permafrost-ecosystem model, including surface soil freeze-thawing processes, to better represent the heat, water, and carbon fluxes in the region. We focused on the surface soil layer, in which an increased thawing depth is now apparent, surface soil moisture, and net primary production. An analysis of observed and model-simulated data indicated that the annual maximum thawing depth (AMTD) had increased gradually on a decadal scale and deepened abruptly after 2005. Climatological analyses of atmospheric water circulation over the region indicated that the recent increases in precipitation over the central Lena River Basin were partly related to cyclone activity. Consequently, the increased precipitation from late-summer to winter resulted in increases in soil moisture, soil temperature, and AMTD in the region.