嘉山地震台大地电场资料真实性分析

分析嘉山地震台自2007年运行以来的大地电场观测资料,并对数据的变化特征进行研究,总结分析部分干扰引起的电场变化的曲线特征,给出不同影响因素导致的曲线异常变化情况,为大地电场干扰排除提供依据.     

Distribution and significance of novel low molecular weight sterenes in an immature evaporitic sediment from the Jinxian Sag,North China

An unusual series of C₂₂–C₂₇ monounsaturated sterenes and C₂₄–C₃₀ tetracyclic terpanes (17,21-secohopanes) were detected in relatively high concentrations in an immature evaporitic marl sediment of the Jinxian Sag, Bohai Bay Basin, North China. The site of unsaturation in these novel sterenes is assigned tentatively to the D ring on the basis of mass spectral interpretation, which also distinguishes them from reported unsaturated sterenes. Other hydrocarbon biomarker or stable isotope characteristics are indicative of microbial (e.g. methyl hopanes), phytoplankton or higher plant (depleted δ¹³C values of isoprenoids and hopanes) inputs and an anoxic carbonate depositional environment (hexacyclic hopanes; tetracyclic terpanes). The hydrocarbon composition showed no obvious biodegradation and the relatively high concentration of unsaturated terpenoids (e.g. gammacerene) and low values of other established maturity parameters (T_s/T_m = 0.23; R_o = 0.44%; T_max = 417 °C), are consistent with sediments of low maturity. The novel, low molecular weight sterenes and the tetracyclic terpanes may be early diagenetic products of microbial sources in a carbonate environment.     

藏东同普杂岩体年代学、地球化学、Sr-Nd同位素特征及大地构造意义

同普杂岩体位于藏东江达地区。本文对该杂岩体岩相学、年代学、主微量元素以及Sr-Nd同位素进行了详细的研究。结果表明,该杂岩体主要由石英闪长岩、花岗闪长岩、含黑云母花岗岩和斑状花岗岩4种岩石类型组成,前三者形成时代分别为262.8±1.5Ma、263.9±1.9Ma、263.7±1.6Ma。其中,含黑云母花岗岩与斑状花岗岩呈渐变过渡关系,它们和花岗闪长岩一起均具有高SiO₂(65.1%~76.6%)、高K₂O+Na₂O(4.84%~8.13%),低MgO(0.25%~2.28%),低FeO^T(0.99%~4.44%),高A/CNK值(除一件样品外两者A/CNK值均大于1.1),以及Ba、Sr、Eu亏损等,均符合强过铝质S型花岗岩的特征。但前两者与后者CaO/Na₂O、Rb/Ba、Rb/Sr值均存在明显差异,哈克图解上也不存在线性关系,表明它们源区存在差异。石英闪长岩则具有相对低的SiO₂(54.2%~55.4%)、低K₂O+Na₂O(3.15%~4.72%),高MgO(3.78%~4.79%),高FeO^T(6.13%~8.09%)等特征。其还具有明显的Nb负异常,不具有Sr的负异常,以及轻稀土相对富集等,均符合岛弧岩浆岩的特征。Sr-Nd同位素特征显示,斑状花岗岩与花岗闪长岩具有相似的初始Sr比值(分别为0.7099,0.7125)和ε_Nd(t)值(分别为-8.6,-10.3),而石英闪长岩则具有较低的初始Sr比值(0.7062),较高的ε_Nd(t)值(1.37)。前两者均落入研究区S型花岗岩与高硅流纹岩区域,后者落在金沙江MORB的下方。通过综合分析,本文认为同普杂岩体形成于火山弧环境,且各岩石类型具有不同的源区:含黑云母花岗岩、斑状花岗岩与花岗闪长岩的源区分别为古老的泥质变质岩和贫泥质的变质砂岩;石英闪长岩则来自富集地幔。表明在晚二叠世早期(~263Ma)金沙江洋盆仍处于俯冲阶段,江达地区主要受金沙江洋盆俯冲消减体系控制而非地幔柱体系。     

Modeling the sediment yield from landslides in the Shihmen Reservoir watershed,Taiwan

Landslides generate enormous volumes of sediment in mountainous watersheds; however, quantifying the downstream transport of landslide‐derived sediment remains a challenge. Landslide erosion and sediment delivery to the Shihmen Reservoir watershed in Taiwan was estimated using empirical landslide frequency–area and volume–area relationships, empirical landslide runout models, and the Hydrological Simulation Program‐ FORTRAN (HSPF). Landslide erosion rates ranged from 0.4 mm yr^‐1 to 2.2 mm yr^‐1 during the period 1986–2003, but increased to 7.9 mm yr^‐1 following Typhoon Aere in 2004. The percentage of landslide sediment delivered to streams decreased from 78% during the period 1986–1997 to 55% in 2004. Although the delivery ratio was lower, the volume of landslide sediment delivered to streams was 2.81 × 10⁶ Mg yr^‐1 in 1986–1997 and 8.60 × 10⁶ Mg yr^‐1 in 2004. Model simulations indicate that only a small proportion of the landslide material was delivered downstream. An average of 13% of the landslide material delivered to rivers was moved downstream during the period 1986–1997. In 2004, the period including Typhoon Aere, the annual fluvial sediment yield accounted for approximately 23% of the landslide material delivered to streams. In general, the transfer of sediment in the fluvial system in the Shihmen Reservoir watershed is dominantly transport limited. The imbalance between sediment supply and transport capacity has resulted in a considerable quantity of landslide material remaining in the upper‐stream regions of the watershed. Copyright © 2012 John Wiley & Sons, Ltd.     

泥石流源地土体应力应变特性对降雨响应过程的分析——以蒋家沟泥石流为例

根据对蒋家沟泥石流源地的崩塌、滑坡、散流坡,在旱季与雨季不同时段,降雨入渗后的土壤含水状况观测,以及泉水季节性变化,详细分析了泥石流源地崩塌、滑坡、散流坡土体的应力应变特性对降雨的响应过程差异.在雨季滑坡临空面和滑坡体内的土体含水量分别为6.67%、4.8%,滑坡活动主要是通过前缘剪出口崩塌方式补给下方沟床.崩塌体由于土体结构极为松散,在雨季该土体含水量通常高达8.85%～16%,使其土体的抗剪强度(C、φ)处于极限应力状态,一旦遇到降雨浸润和冲刷,迅速触变液化,转化为高浓度泥石流的侵蚀产沙过程.     

香溪河流域岩溶洞穴发育与分布特征

结合1∶5万水文地质调查,对香溪河岩溶流域溶洞特征进行了探究,统计其溶洞的规模、形态、发育地层、发育方向及分布高程,结果表明:该区洞穴规模中等,受岩性的控制,溶洞的发育表现出对碳酸盐岩岩组类型的选择性,其中寒武-奥陶系地层溶洞发育程度最高;溶洞的发育方向多为北北东和北北西向,与区域构造线一致,同时受本区构造运动间歇性抬升的影响,溶洞集中发育于4个高程区;从溶洞发育的构造部位来看,溶洞主要分布在宽缓向斜的东南翼及向斜核部,平面分布表现出分带性;该区溶洞多发育至早期就停止进一步发育,其规模、类型、分布特征等与鄂西南地区溶洞均存在差异。      

同位素地球化学方法与地震研究及地震预报

通过在地震活动区对有关地质体的K—Ar、Ar—Ar、FT、TL、~(14)C、ESR、U系等同位素年代学、地下水及其释放气体的D/H、~(13)C/~(12)C、~(18)O/~(16)O等稳定同位素以及He、Ar等稀有气体同位素的研究,可获得有关新构造运动的时间序列、断层运动的时间、地质体热历史以及地下断层流体运动的许多重要信息。因而,同位素地球化学已逐渐在研究地震成因机制以及监测预报地震中发挥重要作用。     

Direct Climatic Effect of Dust Aerosol in the NCAR Community Atmosphere Model Version 3 （CAM3）

Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 W m-2 in the solar spectrum and +0.09 W m-2 in the thermal spectrum on a global average. The magnitude of surface RF is larger than the TOA forcing, with global mean shortwave forcing of-1.76 W m-2 and longwave forcing of +0.31 W m-2 . As a result, dust aerosol causes the absorption of 1.1 W m-2 in t...     

Quantitative assessment on the influence of heavy rainfall on the crystalline schist landslide by monitoring system -case study on Zentoku landslide, Japan

On Shikoku Island, which is one of the four main islands of Japan, a large number of large-scale crystalline schist landslides have been revealed and are being monitored by an observation system. Seasonal heavy rainfall is the most active meteorological factor that can threaten the stability of this kind of site-specific landslide. In this paper, on the basis of the study of the rainfall-related behavior of a typical crystalline schist landslide, the Zentoku landslide, by analyzing the precisely and continuously observed piezometric and movement data, a method was developed to quantitatively assess the effect of heavy rainfall on a large-scale landslide. The results indicated that heavy rainfall-induced landslide displacement shows good correlation with the variation of groundwater levels. Variations of groundwater level have been simulated with the use of a tank model. The simulation using this model permits the change in water levels for future rainfall events to be predicted. By combining the predicted results with the empirical relation between displacements and water levels, rainfall-induced landslide movement during extreme rainfall events can be estimated in advance. The effect of heavy rainfall on sliding behavior can be quantified in terms of the change in displacement. Thus warning information or advisories for the local residents can be provided.