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941.
拉尔玛金矿的生物成矿作用 总被引:1,自引:0,他引:1
位于甘、川两省交界处的拉尔玛金矿床,赋存于下寒武统太阳顶群,矿区内岩浆活动不强烈,矿床中断裂构造较发育,矿石矿物种类较齐全。矿石中的生物有机地球化学特征表明其为细菌和低等藻类生物体衍生的生物标志物和遗传特征,证明了太阳顶群中的有机质起源于菌藻类生物。矿石中的金属矿物生物组构有生物有机胶体组构和矿交代生物组构,说明生物成矿作用经历了直接成矿和间接成矿,即两轮聚矿作用,菌藻生物的第一轮聚金主要形成矿源层,生物的两轮聚金结果,形成此矿床。 相似文献
942.
本文就目前地震台站普遍使用的小规模CMOS电路构成的数字钟元件多、可靠性不高等缺点,提出以INTEL 51系列单片机为核心构成的具有自动校对功能的数字钟,本系统硬件结构简单,系统可靠性强,并可自动根据BMP信号校时,操作简便且精度高。 相似文献
943.
944.
945.
郑庆林 《Acta Meteorologica Sinica》1979,37(1):36-43
文中,非线性项的处理用了变维方法,纬向的“完全的谱方法”及经向的“准谱方法”,既有利于克服非线性不稳定,且能大大节省计算量及存储量,使之能在小型计算机上实现其程序设计。通过设计多个地形曲面的办法来考虑地形的作用。在时间差分格式中,将时间步长取成波数的函数,有利于节省计算量。这模式从一九七四年九月开始进行了较多个例的预报实验,其72小时以内的预报效果是比较好的。 相似文献
946.
COULOMB STRESS CHANGE ON ACTIVE FAULTS IN SICHUAN-YUNNAN REGION AND ITS IMPLICATIONS FOR SEISMIC HAZARD
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Coulomb stress change on active faults is critical for seismic hazard analysis and has been widely used at home and abroad. The Sichuan-Yunnan region is one of the most tectonically and seismically active regions in Mainland China, considering some highly-populated cities and the historical earthquake records in this region, stress evolution and seismic hazard on these active faults capture much attention.
From the physical principal, the occurrence of earthquakes will not only cause stress drop and strain energy release on the seismogenic faults, but also transfer stress to the surrounding faults, hence alter the shear and normal stress on the surrounding faults that may delay, hasten or even trigger subsequent earthquakes. Previously, most studies focus on the coseismic Coulomb stress change according to the elastic dislocation model. However, the gradually plentiful observation data attest to the importance of postseismic viscoelastic relaxation effect during the analysis of seismic interactions, stress evolution along faults and the cumulative effect on the longer time scale of the surrounding fault zone. In this paper, in order to assess the seismic hazard in Sichuan-Yunnan region, based on the elastic dislocation theory and the stratified viscoelastic model, we employ the PSGRN/PSCMP program to calculate the cumulative Coulomb stress change on the main boundary faults and in inner blocks in this region, by combining the influence of coseismic dislocations of the M≥7.0 historical strong earthquakes since the Yongsheng M7.8 earthquake in 1515 in Sichuan-Yunnan region and M≥8.0 events in the neighboring area, and the postseismic viscoelastic relaxation effect of the lower crust and upper mantle.
The results show that the Coulomb stress change increases significantly in the south section of the Xianshuihe Fault, the Anninghe Fault, the northern section of the Xiaojiang Fault, the southern section of the Longmen Shan Fault, the intersection of the Chuxiong-Jianshui Fault and the Xiaojiang Fault, and the Shawan section of the Litang Fault, in which the cumulative Coulomb stress change exceeds 0.1MPa. The assuming different friction coefficient has little effect on the stress change, as for the strike-slip dominated faults, the shear stress change is much larger than the normal stress change, and the shear stress change is the main factor controlling the Coulomb stress change on the fault plane. Meanwhile, we compare the Coulomb stress change in the 10km and 15km depths, and find that for most faults, the results are slightly different. Additionally, based on the existing focal mechanism solutions, we add the focal mechanism solutions of the 5 675 small-medium earthquakes(2.5≤M≤4.9)in Sichuan-Yunnan region from January 2009 to July 2019, and invert the directions of the three principal stresses and the stress shape factor in 0.1°×0.1° grid points; by combining the grid search method, we compare the inverted stress tensors with that from the actual seismic data, and further obtain the optimal stress tensors. Then, we project the stress tensors on the two inverted nodal planes separately, and select the maximum Coulomb stress change to represent the stress change at the node. The results show that the cumulative Coulomb stress change increase in the triple-junction of Sichuan-Yunnan-Tibet region is also significant, and the stress change exceeds 0.1MPa.
Comprehensive analysis of the Coulomb stress change, seismic gaps and seismicity parameters suggest that more attention should be paid to the Anninghe Fault, the northern section of the Xiaojiang Fault, the south section of the Xianshuihe Fault, the southern section of the Longmen Shan Fault and the triple-junction of the Sichuan-Yunnan-Tibet region. These results provide a basis for future seismic hazard analysis in the Sichuan-Yunnan region. 相似文献
947.
948.
Comparison of manual and automatic methods for measurement of methane emission from rice paddy fields 总被引:29,自引:0,他引:29
Zheng Xunhu Wang Mingxing Wang Yuesi Shen Renxing Li Jing J. Heyer M. Kogge Li Laotu Jin Jisheng 《大气科学进展》1998,15(4):569-579
The methane emission flux from rice paddies was simultaneously measured with automatic and manual methods in the suburban of Suzhou. Both methods were based on the static chamber/ GC-FID techniques. Detail analysis of the experimental results indicates: a) The data of methane emission measured with the automatic method is reliable. b) About 11 or 19 o’clock of local time is recommended as the optimum sampling time for the manual spot measurement of methane emission from rice paddies. The methane emission fluxes measured by manual sampling at local time other than the optimum time have to be corrected. The correction coefficient may be determined by automatic and continuous measurement. c) In order to get a more accurate result, an empirical correction factor, such as 18%, is recommended to correct the seasonally total amount of measured methane emission by enlarging the au-tomatically measured data or reducing the manually measured ones. 相似文献
949.
Ulysses 是迄今为止第一次沿独特的日球纬度方向考察日球高纬度空间区域的飞船。本文描述了 Ulysses 飞船的部分主要观测结果,并进行了分析,在 Ulysses 飞船穿越太阳南,北极之前,科学家们提出了各种不同的太阳风速度、磁场等参量的纬向变化模型。分析表明,这些模型都不能解释 Ulysses 飞船的观测结果。Ulysses 飞船的观测对经典的太阳风理论提出了挑战,太阳风的加热与加速是一个远没有被解决的问题。观测与分析表明,经典热传导不可能驱动高速流,太阳风的加速伴随着加热的发生,而加热率大小可能与离子的回旋频率有关;太阳风的热源可能不是单一的形式,而且不同形式的热源对太阳的加热贡献大小与日球径向距离有关。本文讨论并分析了几种可能的太阳风加热与加速机制。 相似文献
950.
详细地介绍了VLBI系统的地面单元中电缆延迟变化的测量方法,这种基于相位的测量方法,为相关领域的高精度延迟测量提供了借鉴。概要介绍了地面单元中电缆测量、反射调制以及相位比较器的工作原理,对各个环节作了数学上的推导分析。给出了一个电缆相对延迟值随温度变化的测试样本。 相似文献