A mechanism for anomalous decline in radon precursory to an earthquake

Mechanisms for interpreting anomalous decreases in radon in ground water prior to earthquakes are examined with the help of a case study to show that radon potentially is a sensitive tracer of strain changes in the crust preceding an earthquake. The 2003 Chengkung earthquake of magnitude (M) 6.8 on December 10, 2003, was the strongest earthquake near the Chengkung area in eastern Taiwan since 1951. The Antung radon-monitoring station was located 20 km from the epicenter. Approximately 65 d prior to the 2003 Chengkung earthquake, precursory changes in radon concentration in ground water were observed. Specifically, radon decreased from a background level of 780 pCi/L to a minimum of 330 pCi/L. The Antung hot spring is situated in a fractured block of tuffaceous sandstone surrounded by ductile mudstone. Given these geological conditions, we hypothesized that the dilation of brittle rock mass occurred at a rate faster than the recharge of pore water and gas saturation developed in newly created cracks preceding the earthquake. Radon partitioning into the gas phase may explain the anomalous decrease of radon precursory to the 2003 Chengkung earthquake. To support the hypothesis, vapor-liquid, two-phase radon-partitioning experiments were conducted at formation temperature (60 degrees C) using formation brine from the Antung hot spring. Experimental data indicated that the decrease in radon required a gas saturation of 10% developed in rock cracks. The observed decline in radon can be correlated with the increase in gas saturation and then with the volumetric strain change for a given fracture porosity.     

Melt Events in A Nascent Mantle Wedge: Implication from the Luobusa Ophiolite,Tibet

The compositions of minerals and whole rocks of the Luobusa ophiolite in South Tibet, a fragment of Neo‐Tethyan forearc lithosphere, is used to investigate the magmatic evolution of nascent mantle wedges in newly‐initiated subduction zones. Clinopyroxenes in the Luobusa peridotites all have diopsidic compositions, and their Al₂O₃ contents vary from ～ 2% in the dunites and refractory harzburgites to 2‐4% in the cpx‐bearing harzburgites. The REE of clinopyroxenes in the harzburgites have left‐sloping patterns with contents comparable to those in abyssal peridotites that have experienced 5‐15% partial melting. Chromites in the Luobusa chromitites have the highest Cr#s (～ 80) and TiO2 contents (0.1‐0.2%), and those in the cpx‐bearing harzburgites have the lowest Cr#s (20‐60) and TiO2 contents (0‐0.1%), whereas those in refractory harzburgites and dunites have intermediate compositions. Cpx‐bearing and refractory harzburgites show spoon‐and U‐shaped REE patterns, respectively, and their HREE distribution patterns suggest at least 15%‐ 20% partial melting. The REE patterns of dunites and high‐Cr chromitites vary from spoon‐ to U‐shaped and require 15‐30% partial melting in their mantle sources to produce their parental melts. Our dataset reveals that the nascent Luobusa mantle wedge was first infiltrated by slab‐derived fluids and later refertilized by transitional lava‐like melts, resulting in cpx‐bearing harzburgites. Partial melting in the deeper cpx‐bearing mantle generated high‐Ca boninitic to arc picritic melts, which interacted with the peridotites in the uppermost mantle to generate high‐Cr chromitites, dunites and some refractory harzburgites. Lithological variation from cpx‐bearing to refractory harzburgites in forearc ophiolites is the result of multi‐stage melt events rather than increasing degrees of partial melting. Intermittent slab rollback during subduction initiation induces asthenospheric upwelling and high heat flux in nascent mantle wedges. Elevated geothermal gradients play a more important role than slab dehydration in triggering Mg‐rich magmatism in newly‐initiated subduction zones.     

雅鲁藏布江缝合带的双陆内俯冲构造与部分熔融层特征──INDEPTH项目结果的初步综合

根据中、美两国合作开展的西藏深反射地震结果,提出雅鲁藏布江缝合带（YZS）的"双陆内俯冲"构造模式和缝合带南、北分别存在着不同特征的、规模不一的部分熔融层;提出YZS处断裂向深部延深有限,认为YZS处地壳增厚有4种机制：①地壳规模的大的俯冲增厚;②上部地壳内的俯冲和背冲增厚;③下地壳内的底部垫托增厚和挤压增厚;④深部熔融体的向上挤入而引起的地壳增厚.提出可能存在两条大的伸展性断裂,造成江孜南、北地块间出现了大升降.     

ELEMENTARY VIEW OF GREENHOUSE EFFECT OF THE ATMOSPHERES OF VARIOUS PLANETS

The global mean temperatures of the atmosphere and the surface of various planets of the solar system are deter-mined by taking the system as in radiative equilibrium,with the atmosphere taken as transparent to solar radiation butwith an albedo α,and composed of N layers each of which absorbs all infrared radiation that falls on it,and a top layerof partial absorptivity a,while the surface is taken as black.It is found that,for the earth's atmosphere with α=0.33,N=0,a=0.83,it gives the current observed mean surface temperature T_s=15℃ and the effective mean radiative temper-ature of the atmosphere T_a=242.6K.On the other hand;the atmosphere of Venus is characterized by α=0.70 andN=70,which yields a surface temperature of about 700K.It is also found that surface evaporation and absorption of solar radiation by the atmosphere tend to lower the sur-face temperature.     

Genesis of Kaolinite Deposits in the Jungar Coalfield,NorthChina: Petrological,Mineralogical and Geochemical Evidence

Petrological, mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield, northern Ordos Basin, North China, define their characteristics, ore genesis and economic interest. Based on the crystalline size, two different types of kaolinite rocks, cryptocrystalline and grainy, were identified under the microscope. XRD data show that kaolinite is the predominant mineral, associated with boehmite, magnesite, anatase, pyrite,diaspore and calcite. However, high boehmite content(mean 70%) shows up in the middle layers. Kaolinite minerals present homogeneous shape and a good crystallinity(HI = 0.96–1.26). Geochemical studies show that the SiO2/Al2 O3 molar ratio of kaolinite is close to the theoretical value, and the contents of Na2 O, K2 O, CaO, MgO are less, suggesting a strong chemical weathering environment. The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite. A Ce anomaly reflects a continental sedimentary environment with shallow water. A temperature range of26.7–34℃ was calculated on the basis of the isotopic signatures(δ18 O, δD) of the kaolinite rocks. All these data indicate that the formation of the kaolinite is caused mainly by the dissolution, coagulation, precipitation and recrystallization of aluminosilicate clastics in acidic conditions. The formation of boehmite in the middle layers indicates that the source rocks have changed. Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis. In addition, it formed by desiliconization of kaolinite under acidic conditions. Due to its high kaolinite content(up to 90%) and low iron mineral content(less than 1%), and good crystallinity, kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future.     

Simplified lateral free field boundary based on a lumped mass system

After reviewing the studies on the lateral artificial boundaries in dynamic soil-structure interactions, the free field boundary was theoretically analyzed in asymmetric-and symmetric-matrix forms. First, the lumped mass system was combined with viscous or viscoelastic elements to obtain a lumped mass-free field boundary. Second, typical examples were implemented using the finite element software ABAQUS. The incident shear wave was taken to be perpendicular to the bottom to verify the effectiven...     

利用卫星影像获得汶川地震之同震地表变形来探讨其断层几何模型(英文)

On 12th May 2008, a MW7.9 earthquake occurred on the Longmenshan fault in the mountains to the west of Sichuan Province, which shook many Asian cities and killed at least 69 000 people.     

海峡两岸及邻近地区暴雨试验IOP608的中尺度对流系统

给出了海峡两岸及邻近地区暴雨试验1998年6月7－10日加密观测期的日平均红外云图的云顶亮温TBB的分布，并通过对逐时红外云图的普查共发现了14个中－α尺度的对汉系统和若干个中－β尺度对流系统，重点分析了6月7日和9日给台湾中部和珠江口带来的暴雨的多个中尺度对流系统连续发生过程及其发生的环境条件，利用可视化系统LiveView展示出了高，低空水平风场和垂直环流之间的联系及湿空气运动的三维轨迹。     

Windows下二维气象绘图软件——客观分析诊断图形系统

客观分析诊断图形系统是一款操作界面友好的二维气象绘图软件，它运行于微软Windows操作系统下，具有多种数据接口，能够绘制等值线、流线、矢量、多种投影地图及不规则数据分布图等多种图形。客观分析诊断图形系统还能够对气象地面、探空数据进行客观分析诊断，并能根据用户所选择气压层、变量由客观分析诊断的结果绘制相应图形。