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91.
The distributions of discrete frequency, N, versus interoccurrence time, t (in days), of M 7 earthquakes in the Taiwan region during the 1900–1994 period, M 6 earthquakes in the north-south seismic belt of China during the 1900–1990 period, and M 5.5 earthquakes in Southern California, U.S.A., during the 1914–1995 period are studied through two statistical models (gamma function and exponential function). Results show that both the exponential function and gamma function can describe the distributions. However, the former is more appropriate than the latter. This indicates that the three time series of earthquakes have a significant component of Poisson processes, even though the tectonic conditions, the fault distributions and the size of the three seismic regions are different. 相似文献
92.
93.
Lung -Chuan Kuo Jung H. Lee Eric J. Essene Donald R. Peacor 《Contributions to Mineralogy and Petrology》1986,94(1):90-98
The occurrence and chemistry of immiscible silicate glasses in a tholeiite mesostasis from the Umtanum formation, Washington, were investigated with transmission electron microscopy and analytical electron microscopy (TEM/AEM). TEM observation reveals isolated, dark globules (2.1 micron or less in diameter) randomly distributed in a transparent matrix glass interstitial to plagioclase laths. The globules less than 0.3 micron and larger than 0.8 micron fall beyond the linear relationship defined by the 0.3–0.8 micron globules in a plot of the logarithm of number versus size. Large globules (0.7 micron or larger in diameter) range from homogeneous to heterogeneous in optical properties and chemistry. Homogeneous globules are completely glassy, whereas heterogeneous globules contain crystalline domains. AEM analyses show that the globules have high Si, Fe, Ca, and Ti with subordinate Mg, Al, P, S, Cl, K, and Mn, which gives high normative fa, px, il, and ap. The matrix glass consists dominantly of Si with low Al and minor Na and K, yielding a high normative qz, or, ab, and an.It is proposed that the silicate liquid immiscibility occurs by reaction of network-modifying cations (NMCs) with dominantly chain-like anionic units in the parental melt to form less polymerized, NMC-bearing units and highly polymerized, Si-rich units. The globules nucleated metastably under supercooled conditions, and medium-size globules become either larger or smaller at lower temperatures. Internal nucleation of NMC-rich phases occurred in some larger globules upon cooling. 相似文献
94.
Hypoxia, periods of reduced dissolved oxygen concentrations, has been observed not only in the Chesapeake Bay but also in the deeper waters of the Virginia estuaries that are tributaries to the Chesapeake Bay. When water temperature exceeded 20°C, minimum oxygen concentrations were observed to be <50% of saturation concentrations in 75%, 50% and 2% of the surveys in the estuaries of the Rappahannock, York and James rivers, respectively. The observation that hypoxia rarely occurred in the James River is surprising, given the fact that it receives the greatest amount of wastewater. Analysis of the oxygen budgets in these estuaries indicates that the variations in the frequency, duration, and severity of hypoxia are related to the net movement of bottom waters. This relationship has significant implications for the management of water quality and marine fisheries. 相似文献
95.
The influence of microcrack density on the elastic and fracture mechanical properties of Stripa granite 总被引:1,自引:0,他引:1
Ove Alm Lise-Lotte Jaktlund Kuo Shaoquan 《Physics of the Earth and Planetary Interiors》1985,40(3):161-179
Microcracks can have a strong influence on the elastic and fracture mechanical properties of rocks if they are numerous, or if they are orientated in unfavourable directions in anisotropic rocks in particular. This paper presents results from a great number of mechanical tests on Stripa granite containing various amounts of microcracks. Variations in the microcrack density were obtained by shock-heating the rock at different temperatures in the range 100–600°C for 3 h.The results presented are obtained from sound velocity measurements, uniaxial compression tests, Brazilian tests and three-point bending tests. The density of microcracks in the heated rock is studied by means of optical microscopy, SEM and differential strain analysis (DSA).Some of the calculated parameters show a maximum value for specimens heat-treated at about 100°C. The tensile strength is, for instance, substantially higher for specimens shock-heated at 100°C than for non-heated ones. Another striking feature is the initial decrease of the diameter observed in specimens heat-treated at 600°C when loaded in uniaxial compression. Both optical microscopy and DSA experiments reveal a large increase in microcracking when the heat-treatment temperature exceeds 300°C. 相似文献
96.
Earthquake epicentroids in the Beijing-Tianjin-Tangshan-Zhangjiakou region inversed by gravity variation data 总被引:1,自引:0,他引:1
Introduction Since the 1960s, gravity changes associated with seismogenesis and earthquake occurrences have been found by many researchers and various physical mechanisms have been proposed to explain these relationship (MEI, 1993; Chen, et al, 1979; Li, Fu, 1983). The US/China joint project beginning in 1981 presented a thorough study of the relationship between gravity variations and earthquake occurrences in the Beijing-Tianjin-Tangshan-Zhangjiakou (BTTZ) region, leading to a combined… 相似文献
97.
98.
首先介绍了伪卫星导航系统的观测方程和动力学模型方程。然后,分析了基于UT变换的UKF算法,针对该算法存在的问题,结合迭代滤波思想和抗差估计原理提出了一种新的抗差UKF算法。并与EKF和UKF算法进行了比较。计算结果表明,该算法不仅可以提高滤波器的精度,而且能够更有效地控制观测异常对导航解的影响,使导航解更能反映导航系统的真实情况。 相似文献
99.
Sohan Lal A. Joshi Sandeep Monu Tomer Parveen Kumar Chun-Hsiang Kuo Che-Min Lin Kuo-Liang Wen M. L. Sharma 《Acta Geophysica》2018,66(4):461-477
On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results. 相似文献
100.
浙江渔场修复振兴暨"一打三整治"(依法打击涉渔"三无"船舶和违反伏休规定等违法生产经营行为,全面开展渔船"船证不符"整治、禁用渔具整治和污染海洋环境行为整治)专项执法行动实施以来,已取得显著成效,但也存在一些问题。文章基于调研所获资料,综合分析涉渔"三无"船舶回潮、部分伏休政策实施困难以及渔船"船证不符"、禁用渔具和海洋环境污染整治不彻底等问题及其原因,提出建立长效机制、加大整治力度和建立省内外联动机制的对策建议,为浙江省海洋生态修复、渔业资源保护和渔业可持续发展的相关决策提供参考。 相似文献