Regional Fault Systems of Qaidam Basin and Adjacent Orogenic Belts

The purpose of this paper is to analyze the regional fault systems of Qaidam basin and ad-jacent orogenic belts. Field investigation and seismic interpretation indicate that five regional fault sys-tans occurred in the Qaidam and adjacent nment.qin belts, controlling the development and evolution of the Qaidam basin. These fault systems are: (1)north Qaidam-Qilian Mountain fault system; (2) south Qaidam-East Kunhm Mountain fault system;（3）Altun strike-slip fault system; (4) Elashan strike-slip fault system, and (5) Gansen-Xiaochaidan fault system. It is indicated that the fault systems controlled the orientation of the Qaidam basin, the formation and distribution of secondary faults within the basin,the migration of depocenters and the distribution of hydrocarbon accmnulation belt.     

Origin of Natural Gas in Kekeya Field, Tarim Basin, China

This paper is mainly concentrated on the geochemical characteristics and origin of gas of Kekeya field in the Tarim basin, NW China. This study shows that Permian mudstone is the main source rock of oil and gas. Based on the carbon isotopes of C1--C4, the carbon isotope of gas in Kekeya field is a little heavier than that in the typical marine-derived gas. The relationship between carbon isotopes of methane and ethane is coincident with Faber equation of gas derived from organic matter Ⅰ/Ⅱ. The majority of gas maturity is estimated, based on the formula, at 1.8%-2.2% besides K2 and K18 wells. In addition, the gas derived from 0.9%-1.2% Ro source rocks may also bemixture. ^40Ar/^36Ar and ^3He/^4He ratios from the gas samples also support the mixing process. Moreover, the gas in this region is mainly generated from more mature source rocks although the low mature gas exists.     

青藏高原与黄土高原毗邻地区晚更新世以来孢粉植物群及沉积环境

本文对青藏高原与黄土高原毗邻地区近20个剖面(点)的黄土沉积进行了孢粉分析表明,自晚更新世以来,研究区黄土剖面中古土壤层的孢粉种类、数量以及木本植物花粉成分均比黄土中多得多,反映了该时期研究区的气候条件比现今要温和湿润,植被较繁茂,以后逐渐旱化,但并不连续。此阶段研究区主要植物群的演替规律是:针叶林→森林草原→草原。     

突发地质灾害气象预警统计模型与应用

通过引入地质灾害潜势度,突发地质灾害气象预警统计模型解决了雨量判据法不能明确表达地质环境条件的问题,在此基础上,提出了潜势度计算、大气降雨变量设计、预警方程优化3方面的改进方法。为提高潜势度计算的准确性,增加了基于卡方检验的地质环境因子独立性判别步骤;对地质环境因子确信程度初始值和权值计算中确信程度变化量初始值设置进行了规定;并将预警模型中累计雨量修正为更为合理的有效累计雨量。在现有的预警方程的基础上提出了基于联合概率分析的预警方程,避免了其与基本地质认识和物理规律存在一定距离、方程系数的意义不明确的局限。以2009年7月2日发布的24 h雨量预报为例,计算结果表明：虽然预报区域面积从101 008 km²减小到27 553 km²,但是地质灾害点落入预报区的比例从44%增加到62%。这说明通过改进的预警模型理论上更加严密,空间准确率有所提高,空报率有所下降。     

Assessment of economic losses from tropical cyclone disasters based on PCA-BP

Tropical cyclones are the most common natural disasters in coastal regions and are the most costly in terms of economic losses. Economic loss assessment is the basis for disaster prevention and alleviation and for insurance indemnification. We use data from 1970 to 2008 for Zhejiang Province, China, in this study evaluating economic losses. We convert direct economic losses from tropical cyclone disasters in Zhejiang Province into indices of direct economic losses. To establish our assessment model, we process disaster-inducing assessment factors, disaster-formative environments and disaster-affected bodies using the principal component analysis method, and we abstract the principal component as the input of a BP neural network model. We found in the actual assessments of five tropical cyclones affecting Zhejiang Province in 2007 and 2008 that the post-disaster loss assessment values of tropical cyclones were higher than the actual losses, but that for more severe storms, the gap was smaller. This reflects the beneficial effect of efforts toward disaster prevention and alleviation for severe tropical cyclones. Pre-assessments based on relatively accurate forecast values of wind and precipitation at the start of a tropical cyclone have been in accordance with the post-disaster assessment values, while the pre-assessment results using less accurate forecast values have been unsatisfactory. Therefore, this model can be applied in the actual assessment of direct economic loss from tropical cyclone damage, but increasingly accurate forecasting of wind and precipitation remains crucial to improving the accuracy of pre-assessments.     

四川省都江堰市龙池地区泥石流危险性评价研究

汶川地震灾区震后泥石流灾害较震前活跃,对灾区泥石流危险性进行评价是灾后重建过程中合理防灾减灾的基础工作。通过研究泥石流灾害事件中的泥石流规模、泥石流沟堆积扇面积及相应的灾害损失等基础资料,提出以泥石流在泥石流沟堆积扇上的平均堆积厚度替代泥石流规模作为主要危险因子的单沟泥石流危险性评价方法。用该方法对汶川震区都江堰市龙池镇龙溪河流域2010年"8.13"泥石流事件中的29条沟谷型泥石流进行危险性评价,评价结果中9条为高度危险,12条为中度危险,8条为低度危险。用以泥石流规模为主要危险因子的单沟泥石流危险性评价方法进行对比评价,2种评价方法中有65.5%的泥石流的危险性评价结果一致。以泥石流沟堆积扇平均堆积厚度为主要危险因子的单沟泥石流危险性评价方法更能突出规模对泥石流综合危险度的贡献,能更好地反映小泥石流流域和小泥石流堆积扇的泥石流在中小规模的泥石流总量下的危险程度。     

Radioactive elements in natural gas: a case study on distribution of gaseous 222radon and its origin mechanism

As natural gas becomes increasingly important in our daily life, studies have been carried out on trace elements such as mercury and arsenic within it. Other than those, the existence of radioactive gaseous radon from the combustion of natural gas indoors can cause severe diseases and damages to body organs, putting a hazardous impact on human health. At the same time, the radon can also corrode gas production and transportation equipment. A review of the literature on radon concentrations in natural gas produced from gas reservoirs in China and other countries have been studied. Radon is a decay product from ²³⁸U, which is closely related to the accumulation and migration of organic matter during diagenesis. Gas recovered from reservoirs with higher than average natural ²³⁸U contains higher than average levels of ²²²Rn. Massive fault systems and fracture zones appear to play a significant role in radon concentrations in natural gas.     

断陷湖盆滩坝砂体成因与成藏:以东营凹陷沙四上亚段为例

滩坝砂是一种发育在滨浅湖高能环境的薄互层沉积,是以往未被重视的、认识程度较低的碎屑岩储集体。围绕滩坝砂成因与成藏的难点,研究了东营凹陷沙四上亚段滩坝砂沉积特征和分布规律,明确了滩坝砂成藏要素与富集规律。提出了滩坝砂沉积受古地貌、古水动力(波浪、湖流)和古基准面控制的"三古控砂"机制和油气成藏受断裂裂隙、有效储层、烃源岩超压控制的"三元控藏"认识,指出断陷盆地中长期基准面持续上升,短期基准面频繁震荡形成了大面积分布的滨浅湖滩坝砂沉积,烃源岩生烃增压与成岩过程中耗水降压共同作用下的"压-吸充注"是滩坝砂岩大面积含油的主要原因。     

贵州北盘江特大桥岩体工程地质评价

针对西部峡谷地区的公路大桥勘察的主要工程地质间题,如桥塔边坡稳定性问题、桥基、持力层选择间题等,以贵州省关(岭)兴(义)高等级公路北盘江特大桥主要岩土工程问题分析为例,根据岩体非线性变形破坏理论,结合岩体结构面模拟及Hock-Brown强度曲线,确定了桥位区斜坡的潜在滑动面、对该桥梁勘察中的高边坡稳定性问题、岩溶地质间题、桥位持力层选择问题以及桥基承载力问题作了进一步探讨,为实际工程的设计奠定了地质基础。     

Geochemical distribution and removal of As,Fe, Mn and Al in a surface water system affected by acid mine drainage at a coalfield in Southwestern China

The chemical characteristics, formation and natural attenuation of pollutants in the coal acid mine drainage (AMD) at Xingren coalfield, Southwest China, are discussed in this paper based on the results of a geochemical investigation as well as geological and hydrogeological background information. The chemical composition of the AMD is controlled by the dissolution of sulfide minerals in the coal seam, the initial composition of the groundwater and the water–rock interaction. The AMD is characterized by high sulfate concentrations, high levels of dissolved metals (Fe, Al, Mn, etc.) and low pH values. Ca²⁺ and SO₄ ²⁻ are the dominant cation and anion in the AMD, respectively, while Ca²⁺ and HCO₃ ⁻ are present at significant levels in background water and surface water after the drainage leaves the mine site. The pH and alkalinity increase asymptotically with the distance along the flow path, while concentrations of sulfate, ferrous iron, aluminum and manganese are typically controlled by the deposition of secondary minerals. Low concentrations of As and other pollutants in the surface waters of the Xingren coalfield could be due to relatively low quantities being released from coal seams, to adsorption and coprecipitation on secondary minerals in stream sediments, and to dilution by unpolluted surface recharge. Although As is not the most serious water quality problem in the Xingren region at present, it is still a potential environmental problem. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.