On the frequency distribution of interoccurrence times of earthquakes     

Jeen-Hwa Wang  Chiao-Hui Kuo 《Journal of Seismology》1998,2(4):351-358

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   

三层准地转斜压模式中的准常定波与平流层极涡形成，维持和演变的机制     

郭卫东  纪立人 《大气科学》1988,12(S1):176-190

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Petrology of spinel harzburgite xenoliths from the Kishb Plateau,Saudi Arabia     

Lung -Chuan Kuo  Eric J. Essene 《Contributions to Mineralogy and Petrology》1986,93(3):335-346

Two spinel harzburgite xenoliths from a Pleistocene alkali basalt unit erupted at the northwestern corner of the Tertiary Kishb Plateau (Saudi Arabia) are characterized by an incipient transition from protogranular to porphyroclastic texture. Vermicular and interstitial spinels are closely associated with neoblasts of olivine, enstatite, and diopside. Sparse exsolution lamellae of high-Ca pyroxene occur in all the enstatite porphyroblasts. Olivine neoblasts are, in many cases, in contact with one another, with the triple grain junctions rarely approaching 120°. Chemical zoning is undetectable by microprobe in spinel and olivine, whereas zoning of Al in enstatite and diopside indicates that chemical equilibrium was not attained. Clear, palegreen glasses occur as veinlets about 10 microns or less in width along grain boundaries and cracks. Consistent counting rates for Na in these glasses were obtained only at 5 kV with a sample current of about 6 namps and counting time of less than 7 s. These glasses are chemically homogeneous and are characterized by relatively high contents of SiO₂ (55.8–58.7 wt%), Na₂O (6.4–7.6 wt%), and Al₂O₃ (20.0–21.6 wt%), with inferred volatile contents of less than 1 wt%. The glass is suggested to be of upper mantle origin rather than having developed from the host basalt or by decompressional melting upon ascent.Geothermometry and geobarometry indicate that the lithospheric upper mantle beneath the Arabian Shield had been locally heated to higher than 1,050° C during Miocene/ Pliocene, resulting in some degree of partial melting. Spinel was formed by reaction between aluminous pyroxenes and olivine during subsequent cooling, and intercrystalline Mg-Fe exchange reached a steady state at about 800° C. The geotherm beneath the Arabian Shield since Miocene is estimated to be somewhat lower than that representing the present oceanic upper mantle. The thermal history established is consistent with the tectonic history of the Red Sea area and indicates a two-stage magmatism in the Arabian Shield since Miocene.  相似文献   

Occurrence,chemistry, and origin of immiscible silicate glasses in a tholeiitic basalt: A TEM/AEM study     

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   

Hypoxia and salinity in Virginia estuaries     

Albert Y. Kuo  Bruce J. Neilson 《Estuaries and Coasts》1987,10(4):277-283

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   

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   

Earthquake epicentroids in the Beijing-Tianjin-Tangshan-Zhangjiakou region inversed by gravity variation data   总被引：1，自引：0，他引：1  

郑金涵  宋胜合  刘克人  卢红艳  郭宗汾 《地震学报(英文版)》2003,16(4):449-458

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   

深源成矿物质与深部找矿分析   总被引：1，自引：0，他引：1  

张阔  赵闯  牛树银  孙爱群  王宝德  闫军印 《吉林地质》2008,27(4)

本文认为金银铅锌等成矿物质主要来自核—幔源区,通过地幔热柱多级演化迁移到地壳上部,在较好的构造扩容带中集聚成矿,而围岩萃取的成矿物质较为有限,不应花费很大精力去寻找所谓矿源层,而要侧重研究构造成矿控矿作用,对新一轮地质找矿和资源评价,特别是一些老矿山的深部、外围找矿有重要的参考价值。  相似文献   

UKF的改进算法及其在伪卫星定位中的应用     

LI Xue-peng  ZHANG You-qun  BAO Kuo 《测绘学院学报》2008,(2)

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   

Temporal and spatial variations of post-seismic deformation following the 1999 Chi-Chi, Taiwan earthquake     

Ya-Ju Hsu  Paul Segall  Shui-Beih Yu  Long-Chen Kuo  Charles A. Williams 《Geophysical Journal International》2007,169(2):367-379

We use GPS displacements collected in the 15 months after the 1999 Chi-Chi, Taiwan earthquake  ( M _w 7.6)  to evaluate whether post-seismic deformation is better explained by afterslip or viscoelastic relaxation of the lower crust and upper mantle. We find that all viscoelastic models tested fail to fit the general features in the post-seismic GPS displacements, in contrast to the satisfactory fit obtained with afterslip models. We conclude that afterslip is the dominant mechanism in the 15-month period, and invert for the space–time distribution of afterslip, using the Extended Network Inversion Filter. Our results show high slip rates surrounding the region of greatest coseismic slip. The slip-rate distribution remains roughly stationary over the 15-month period. In contrast to the limited coseismic slip on the décollement, afterslip is prominent there. Maximum afterslip of 0.57 m occurs downdip and to the east of the hypocentral region. Afterslip at hypocentral depths is limited to the southern part of the main shock rupture, with little or no slip on the northern section where coseismic slip was greatest. Whether this results from along strike variations in frictional properties or dynamic conditions that locally favour stable sliding is not clear. In general, afterslip surrounds the area of greatest coseismic slip, consistent with post-seismic slip driven by the main shock stress change. The total accumulated geodetic afterslip moment is  3.8 × 10¹⁹ N m  , significantly more than the seismic moment released by aftershocks,  6.6 × 10¹⁸ N m  . Afterslip and aftershocks appear to have different temporal evolutions and some spatial correlations, suggesting that aftershock rates may not be completely controlled by the rate of afterslip.  相似文献