洪涝统计方法探讨

利用深圳气象台1953--2005年的雨量资料，对洪涝的两种统计方法进行了对比分析，并引出了更为科学和合理的“任意连续10d／20d雨量统计洪涝的方法”。通过检验，该方法能够较准确地反映洪涝灾害的实际情况。     

河南省冬小麦干旱规律分析

根据河南省104个气象站1957 2000年降水量资料,以冬小麦全生育期降水负距平(%)为干旱指标,提取不同等级干旱的资料矩阵进行经验正交函数分解,并取主要模态特征向量值和时间系数进行分析,结果表明:河南省冬小麦干旱以轻旱和中旱为主要特征,40余年轻旱、中旱发生频率达59.71%和32.24%;各等级干旱的空间分布均表现为豫北、豫东以及豫西北的部分地区是干旱频发区,而豫西南和豫南地区则是干旱低发区;干旱的时间变化呈波峰波谷交替的振动形式,大规模轻旱2~3 a一遇,中旱3~4 a一遇,重旱约10 a一遇。降水负距平(%)平均值的分布特征可从总体上体现干旱的时空变化规律。     

洛阳地区雷暴活动规律和雷灾分析

利用洛阳市及9县10个观测站1966-2005年的雷暴观测资料,统计分析了洛阳地区雷暴活动时空分布特征,结果显示:洛阳地区雷暴时空分布很不均匀,栾川、嵩县、孟津偏多,宜阳、新安、汝阳偏少,南北多中部少;20世纪60年代中期到70年代雷暴日数偏多,80年代至今雷暴日数偏少,但从80年代开始,洛阳地区雷暴日数有缓慢上升的趋势,年际变化幅度大,季节性特点非常明显,集中出现在4-9月,而夏季雷暴日数接近全年的80%。洛阳地区雷击人员伤亡事件主要发生在农村,造成的财产损失主要在市区,近年来雷击次数及所造成的损失呈上升趋势。     

Interactions between basalts and oil source rocks in rift basins： CO2 generation

Basalts interbedded with oil source rocks are discovered frequently in rift basins of eastern China, where CO2 is found in reservoirs around or within basalts, for example in the Binnan reservoir of the Dongying Depression. In the reservoirs, CO2 with heavy carbon isotopic composition (δ13C>-10‰ PDB) is in most cases accounts for 40% of the total gas reserve, and is believed to have resulted from degassing of basaltic magma from the mantle. In their investigations of the Binnan reservoir, the authors suggested that the CO2 would result from interactions between the source rocks and basalts. As the source rocks around basalts are rich in carbonate minerals, volcanic minerals, transition metals and organic matter, during their burial history some of the transition metals were catalyzed on the thermal degradation of organic matter into hydrocarbons and on the decomposition of carbonate minerals into CO2, which was reproduced in thermal simulations of the source rocks with the transition metals (Ni and Co). This kind of CO2 accounts for 55%-85% of the total gas reserve generated in the process of thermal simulation, and its δ13C values range from -11‰- -7.2‰ PDB, which are very similar to those of CO2 found in the Binnan reservoir. The co-generation of CO2 and hydrocarbon gases makes it possible their accumulation together in one trap. In other words, if the CO2 resulted directly from degassing of basaltic magma or was derived from the mantle, it could not be accumulated with hydrocarbon gases because it came into the basin much earlier than hydrocarbon generation and much earlier than trap formation. Therefore, the source rocks around basalts generated hydrocarbons and CO2 simultaneously through catalysis of Co and Ni transition metals, which is useful for the explanation of co-accumulation of hydrocarbon gases and CO2 in rift basins in eastern China.     

鄂尔多斯盆地靖边潜台及其周边地区中奥陶统马家沟组马五1-4亚段储层非均质性主要控制因素

鄂尔多斯盆地靖边潜台及相邻区域在马五1-4时总体上为(内)陆棚盆缘坪亚环境.储层主要岩性为粉晶白云岩及含硬石膏结核和/或柱状晶的粉晶白云岩.地层在岩性上的分布差异是控制储层非均质发育的基础性因素,以含硬石膏结核和/或柱状晶的粉晶白云岩对研究区更具控制意义.其他主要控制因素还有地质背景、古岩溶成岩作用、构造裂隙及断层分布等,古地貌、储层有效厚度以及非储层发育程度等对储层非均质性也具一定影响.靖边潜台为目前天然气主产区,靠近研究区的西侧和东侧的储集性均较差,西侧地层剥蚀严重,东侧溶蚀作用过于强烈,储集性能均遭到严重破坏.     

High Precision Time Domain Forward Modeling for Crosshole Electromagnetic Tomography

To improve the resolution of crosshole electromagnetic tomography, high precision of forward modeling is necessary. A pseudo-spectral time domain (PSTD) forward modeling was used to simulate electromagnetic wave propagation between two boreholes. The PSTD algorithm is based on the finite difference time domain (FDTD) method and uses the fast Fourier transform (FFT) algorithm for spatial derivatives in Maxwell's equations. Besides having the strongpoint of the FDTD method, the calculation precision of the PSTD algorithm is higher than that of the FDTD method under the same calculation condition. The forward modeling using the PSTD method will play an important role in enhancing the resolution of crosshole electromagnetic tomography.     

Constraining the stepwise migration of the eastern Tibetan Plateau margin by apatite fission track thermochronology

Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in this study. The measured fission track apparent ages, combined with the simulated annealing mod- eling of the thermal history, have been used to reconstruct the thermal evolutionary histories of the samples and interpret the active history of the thrusts and faults in these areas. Thermal history mod- eling shows that earlier tectonic cooling occurred in the Garzê-Litang thrust in Miocene (~20―16 Ma) whereas the later cooling occurred mainly in the Longmen Shan thrust since ~5 Ma. Our study sug- gests that the margin of eastern Tibetan Plateau was extended by stages: through strike-slip faults deformations and related thrusts, the upper crust formed the Garzê-Litang margin in the Miocene epoch and then moved to the Longmen Shan margin since ~5 Ma. During this process, the deformations of different phases in the eastern Tibetan Plateau were absorbed by the thrusts within them and conse- quently the tectonic events of long-distance slip and extrusion up to hundreds of kilometers have not been found.     

Geological analysis and FT dating of the large-scale right-lateral strike-slip movement of the Red River fault zone

Tectonically, the large-scale right-lateral strike-slip movement along the Red River fault zone is char-acterized at its late phase with the southeastward extension and deformation of the Northwestern Yunnan normal fault depression on its northern segment, and the dextral shear displacement on its central-southern segment. Research of the relations between stratum deformation and fault movement on the typical fault segments, such as Jianchuan, southeast Midu, Yuanjiang River, Yuanyang, etc. since the Miocene Epoch shows that there are two times dextral faulting dominated by normal shearing occurring along the Red River fault zone since the Miocene Epoch. The fission track dating (abbrevi-ated to FT dating, the same below) is conducted on apatite samples collected from the above fault segments and relating to these movements. Based on the measured single grain’s age and the con-fined track length, we choose the Laslet annealing model to retrieve the thermal history of the samples, and the results show that the fault zone experienced two times obvious shear displacement, one in 5.5 ± 1.5 MaBP and the other in 2.1± 0.8 MaBP. The central-southern segment sees two intensive uplifts of mountain mass in the Yuanjiang River-Yuanyang region at 3.6―3.8 MaBP and 1.6―2.3 MaBP, which correspond to the above-mentioned two dextral normal displacement events since the late Miocene Epoch.     

Microbialite of anoxic condition from Permian-Triassic transition in Guizhou,China

Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.     

三维地震数据可视化原理及方法

可视化是实现三维地震数据真三维解释的有效方法,本文介绍了三维地震数据可视化的基本原理,论述了用光线投射算法实现可视化的主要步骤,详细推导了合成可视化图像的计算公式,分析了阻光度曲线的物理意义及对可视化图像的调节作用,并用两个实际三维地震数据进行了试验.结果表明该方法能够由原始三维地震数据直接对地质体进行成像,能将分散的、孤立的信息互相联系起来,揭示隐藏在数据中的地质现象和规律.