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991.
Applying genetic algorithm to inversion of seismic moment tensor solution and using the data of P waveform from digital network
and initial motion directions of P waves of Taiwan network stations, we studied the moment tensor solutions and focal parameters
of the earthquake of M=7.3 on 16 September of 1994 in Taiwan Strait and other four quakes of M
L≥5.8 in the near region (21°–26°N, 115°–120°E). Among the five earthquakes, the quake of M=7.3 on September 16, 1994 in Taiwan Strait is the strongest one in the southeastern coast area since Nan’ao earthquake of
M=7.3 in 1918. The results show that moment tensor solution of M=7.3 earthquake is mainly double-couple component, and is normal fault whose fault plane is near NW. The strike of the fault
plane resembles that of the distributive bands of earthquakes before the main event and fracture pattern shown by aftershocks.
The tension stress axis of focal mechanism is about horizontal, near in NE strike, the compressive stress axis is approximately
vertical, near in NWW strike. It seems that this quake is controlled by the force of Philippine plate’s pressing Eurasian
plate in NW direction. But from the viewpoint of P axis of near vertical and T axis of near horizontal, it is a normal fault of strong tensibility. There are relatively big difference between focal mechanism
solution of this quake and those of the four other strong quakes. The complexity of source mechanism solution of these quakes
represents the complexity of the process of the strait earthquake sequences.
Contribution No. 98A01001, Institute of Geophysics, State Seismological Bureau, China.
The subject is supported and helped by Academician Yun-Tai CHEN, Profs. Qing-Yao HONG, Zhen-Xing YAO, Tian-Yu ZHENG, Yao-Lin SHI, Ji-An XU, Bo-Shou HUANG and colleague Mei-Jian AN, Xue-Reng DING, Rui-Feng LIU. De-Chong ZHANG and Ming Li provided the digital data warm-heartedly. Lin-Ying WANG offered us the catalogue of earthquakes in southeastern coastal area in China. Xi-Li WANG and Tong-Xia BAI provided us the issued annual reports data. The authors would like to express their gratitude to all of these people.
This paper is sponsored by the National Natural Science Foundation of China and Scientific and Technological Commission of
Shantou, Guangdong Province. 相似文献
992.
地震前兆场的演化和能量非线性聚集的关系 总被引:4,自引:1,他引:3
运用非均匀介质中“非线性振动的局域能量聚集”过程,模拟唐山7.8级和大同6.1级地震的前兆场演化,发现地震孕育过程中出现的诸多前兆特征与地壳内构造能量的非线性聚集有关。 相似文献
993.
You-Kuan Zhang Jie Lin 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(2):117-140
Transport of non-ergodic solute plumes by steady-state groundwater flow with a uniform mean velocity, μ, were simulated with Monte Carlo approach in a two-dimensional heterogeneous and statistically isotropic aquifer whose transmissivity,
T, is log-normally distributed with an exponential covariance. The ensemble averages of the second spatial moments of the plume
about its center of mass, <S
i
i
(t)>, and the plume centroid covariance, R
i
i
(t) (i=1,2), were simulated for the variance of Y=log T, σ
Y
2=0.1, 0.5 and 1.0 and line sources normal or parallel to μ of three dimensionless lengths, 1, 5, and 10. For σ
Y
2=0.1, all simulated <S
i
i
(t)>−S
i
i
(0) and R
i
i
(t) agree well with the first-order theoretical values, where S
i
i
(0) are the initial values of S
i
i
(t). For σ
Y
2=0.5 and 1.0 and the line sources normal to μ, the simulated longitudinal moments, <S
11(t)>−S
11(0) and R
11(t), agree well with the first-order theoretical results but the simulated transverse moments <S
22(t)>−S
22(0) and R
22(t) are significantly larger than the first-order values. For the same two larger values of σ
Y
2 but the line sources parallel to μ, the simulated <S
11(t)>−S
11(0) are larger than but the simulated R
11 are smaller than the first-order values, and both simulated <S
22(t)>−S
22(0) and R
22(t) stay larger than the first-order values. For a fixed value of σ
Y
2, the summations of <S
i
i
(t)>−S
i
i
(0) and R
i
i
, i.e., X
i
i
(i=1,2), remain almost the same no matter what kind of source simulated. The simulated X
11 are in good agreement with the first-order theory but the simulated X
22 are significantly larger than the first-order values. The simulated X
22, however, are in excellent agreement with a previous modeling result and both of them are very close to the values derived
using Corrsin's conjecture. It is found that the transverse moments may be significantly underestimated if less accurate hydraulic
head solutions are used and that the decreasing of <S
22(t)>−S
22(0) with time or a negative effective dispersivity, defined as , may happen in the case of a line source parallel to μ where σ
Y
2 is small. 相似文献
994.
氧化铬柱支撑蒙脱石的制备研究 总被引:4,自引:1,他引:3
以浙江和新疆的膨润土为原料合成了氧化铝柱支撑蒙脱石,成柱溶液以Na2CO3为碱水解铝盐溶液制得。因为制备含有大聚羟基铬阳离子的成柱溶液是获得具有大的基面间距的柱支撑粘土的关键,我们详细研究了CO32-/Cr3+值、水解温度和水解时间对所得柱支撑蒙脱石性质的影响。聚羟基铬阳离子通过阳离子交换引入蒙脱石,所得产物用X射线衍射分析和BET氮比表面等方法研究。所得氧化铝柱支撑蒙脱石(简称Cr-mont)的基面间距为2.55nm,BET氮比表面积为190~230m2/g。 相似文献
995.
前陆盆地类型及其沉积动力学研究综述 总被引:17,自引:2,他引:15
从前陆盆地的特点及类型入手,综述了前陆盆地研究的热点内容,最新方法及其沉积动力学进展状况,揭示了前陆背景下盆地充填序列的构成及内部演化特征,指出了盆地的沉积-地层格架与冲断造山带的幕式活动之间的响应关系。 相似文献
996.
研究了文献[2]提出的结线动力无穷元的特性及其参数确定。由于这种单元将衰减函数定义在无穷向结线上,从而不仅可同时考虑多种波动形式,而且对于不同介质,不必通过改变节点坐标分布的形式实现介质间的过渡,而直接以结线上参数的改变来实现,因而可以更好地模拟无穷波动场,使用起来更方便.更容易推广。 相似文献
997.
In three polished thin sections of Yamato 791717 (CO3). fifty-five Ca, Al-rich inclusions were found, which include two hibonite-bearing,
eight melilite-rich and forty-five spinel-pyroxene inclusions. Based on the petrography and mineral chemistry of the inclusions,
it is proposed that the melilite-rich inclusions and spinel-pyroxene inclusions condensed in the solar nebula, and the hibonite-bearing
inclusions crystallized from melts. The heavy alteration of the inclusions in Yamato 791717, which probably took place under
a very oxidizing condition in the solar nebular, is also confirmed.
Project supported by the National Natural Science Foundation of China (Grant No. 49673200). and by the Japanese Society for
Promotion of Sciences (JSPS). 相似文献
998.
Models of corundum origin from alkali basaltic terrains: a reappraisal 总被引:10,自引:0,他引:10
F. Lin Sutherland Paul W. O. Hoskin C. Mark Fanning Robert R. Coenraads 《Contributions to Mineralogy and Petrology》1998,133(4):356-372
Corundums from basalt fields, particularly in Australia and Asia, include a dominant blue-green-yellow zoned “magmatic” suite
(BGY suite) and subsidiary vari-coloured “metamorphic” suites. The BGY corundums have distinctive trace element contents (up
to 0.04 wt% Ga2O3 and low Cr/Ga and Ti/Ga ratios <1). Different melt origins for BGY corundums are considered here from their inclusion and
intergrowth mineralogy, petrologic associations and tectonic setting. Analysed primary inclusion minerals (over 100 inclusions)
cover typical feldspars, zircon and Nb-Ta oxides and also include hercynite-magnetite, gahnospinel, rutile-ilmenite solid
solution, calcic plagioclase, Ni-rich pyrrhotite, thorite and low-Si and Fe-rich glassy inclusions. This widens a previous
inclusion survey; New England, East Australia corundums contain the most diverse inclusion suite known from basalt fields
(20 phases). Zircon inclusion, intergrowth and megacryst rare earth element data show similar patterns, except for Eu which
shows variable depletion. Temperature estimates from magnetite exsolution, feldspar compositions and fluid inclusion homogenization
suggest that some corundums crystallized between 685–900 °C. Overlap of inclusion Nb, Ta oxide compositions with new comparative
data from niobium-yttrium-fluorine enriched granitic pegmatites favour a silicate melt origin for the corundums. The feasibility
of crystallizing corundum from low-volume initial melting of amphibole-bearing mantle assemblages was tested using the MELTS
program on amphibole-pyroxenite xenolith chemistry from basalts. Corundum appears in the calculations at 720–880 °C and 0.7–1.1 GPa
with residual feldspathic assemblages that match mineral compositions found in corundums and their related xenoliths. A model
that generates melts from amphibole-bearing lithospheric mantle during magmatic plume activity is proposed for BGY corundum
formation.
Received: 3 January 1997 / Accepted: 8 July 1998 相似文献
999.
Based on the method of "two-dimensional depth structure of the crust" proposed by Horiuchi et al., about 5000 arrival times of 303 local shallow earthquakes recorded by the Beijing Seismographic Network from 1990 ~ 1993 are used to investigate the depth distribution of Moho discontinuity beneath Beijing and its adjacent area. We simultaneously determined the hypocenter parameters and P- and S-wave station corrections. The data of the North China Network were also investigated. The results are as follows: (1) The depth distribution of Moho discontinuity becomes shallower from the northwest to the southeast, i.e., in Zhangjiakou area, the Moho discontinuity is located at a depth range from 40~42 km. In the Beijing area, it is 36~39 km. However, at the eastern and southeastern part of this area, it is only 28-30 km and 30~32 km, respectively. (2) Beneath the Tangshan area, there is another elliptic interface shallower than the Moho discontinuity. Separately, its major and minor axis is approximately along 相似文献
1000.
北淮阳盆岭构造带是大别造山带的重要组成部分。佛子岭岩群代表了早古生代扬子地块北缘大别古岛弧弧前海盆的火山沉积建造,在加里东运动陆块对接过程中变形变质。石炭系梅山群具磨拉石建造特征。在华力西印支期陆内俯冲褶皱带的基础上,燕山期沿桐柏桐城断裂伸展北移,近东西向断陷盆地发育,形成盆岭构造景观。南侧大别山强烈隆升,铸就了现今大别山变质核杂岩构造格局。中生代岩浆活动是区内重要铀源,具有成矿潜力的地质体是响洪甸正长岩体和北带粗面质火山碎屑岩 相似文献