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991.
对中国西部大开发战略中防震减灾工作的思考 总被引:2,自引:0,他引:2
阐述了防震减灾工作在中国西部大开发战略中的地位和作用 ,做好西部大开发战略中防震减灾工作的指导思想以及西部防震减灾工作的现状、问题和建议 相似文献
992.
993.
994.
995.
分析了四川冕宁大桥水库坝区和库区的水地质和工程地质条件,由于库区内断裂比较发育,因此,水库蓄水后,库水将会下渗,易于发生诱发地震,由于大坝和库区位于安宁河断裂中段,因此应注意该段发生诱发地震的可能性,库坝区边坡较稳定,但是近库坝区局部边坡有失稳的可能性,虽然不致于影响水库的正常运行,但是也应引起重视。 相似文献
996.
997.
Study on coupling between deep and shallow structures of Xingtai area and some significant questions
IntroductionIn order to gain a clear idea of the deep tectonic environment of Xingtai earthquake area,three wide-angle deep seismic renectionlrefraction profiles have been conducted through the are4they are Yuanshi--Ji'nan profile, Renxian--Wuqing profile and Tat' an--LongyaM inzhou profi I e.The Yuanshi--Ji'nan profile passes through the epicenter of the Ms=7.2 main shock andTat' ~ongyaO--X inzhou profi ie passes through the ep icenter of the Ms=6. 8 earthquake. Duringthe "Eighth Five-… 相似文献
998.
LONG Si-sheng 《地震学报(英文版)》2000,13(5):491-498
Twenty-two earthquakes (M
L=2.2–3.7) in the joint region of Xianshuihe, Longmenshan and An’ninghe faults are studied in this paper. The source mechanism
solutions of these events are obtained using P-wave first motion method, and the characteristics of the source stress field
and rupture in the joint region are summarized preliminarily with some results of other researchers. Being strongly extruded
by the approximately horizontal regional stress with the direction from north-west to south-east and the effect of the complex
tectonics in the region, the source stress field has complex and variable characteristics. The earthquakes mainly show normal
or strike-slip faults in Yajiang, North-triangle and west of Chengdu-block areas, indicating that the vertical forces have
been playing an important role in the source stress fields, while the earthquakes mainly show reverse or strike-slip faults
in Baoxing-Tianquan area, with the horizontal components of the principal pressure stress axes identical to the south-west
direction to which the shallow mass is moving. We think that the manifold combinations of earthquake faults are the micro-mechanism
based upon which the large regional shallow crust mass has been moving continually. 相似文献
999.
Present-day tectonic movement in the northeastern margin of the Qinghai-Xizang (Tibetan) plateau as revealed by earthquake activity 总被引:2,自引:0,他引:2
Characteristics of present-day tectonic movement in the northeastern margin of Qinghai-Xizang plateau (Tibetan) are studied
based on earthquake data. Evidence of earthquake activity shows that junctures between blocks in this area consist of complicated
deformation zones. Between the Gansu-Qinghai block and Alxa block there is a broad compressive deformation zone, which turns
essentially to be a network-like deformation region to the southeast. The Liupanshan region, where the Gansu-Qinghai block
contacts the Ordos block, is suffering from NE-SW compressive deformation. Junction zone between the Ordos and Alxa block
is a shear zone with sections of variable trend. The northwestern and southeastern marginal region of the Ordos is under NNW-SSE
extension. The above characteristics of present-day tectonic deformation of the northeastern Qinghai-Xizang plateau may be
attributed to the northeastward squeezing of the plateau and the resistance of the Ordos block, as well as the southeastward
extrusion of the plateau materials.
Foundation item: State Natural Science Foundation of China (49732090) and the Development Program on National Key Basic Researches under
the Project Mechanism and Prediction of Continental Strong Earthquakes (95-13-02-05).
Contribution No. 00FE2003, Institute of Geophysics, China Seismological Bureau. 相似文献
1000.
C. Narteau E. Blanter J. -L. Le Mouël M. Shirnman C. J. Allgre 《Physics of the Earth and Planetary Interiors》2000,120(4):271-287
We investigate the temporal evolution of the magnetic dipole field intensity of the Earth through a multiscale dynamo mechanism. On a large range of spatio-temporal scales, the helical motions of the fluid flow are given by a schematic model of a fully developed turbulence. The system construction is symmetric with respect to left-handed and right-handed cyclones. The multiscale cyclonic turbulence coupled with a differential rotation (schematic ω dynamo) or alone (schematic 2 dynamo) is the ingredient of the loop through which poloidal and toroidal fields are built from one another. Two kinds of reaction of the magnetic field on the flow are considered: the presence of a magnetic field first favours a larger-scale organization of the flow, and, second, impedes this flow by the effect of growing Lorentz forces. We obtain the general features of the geomagnetic field intensity observed over geological times and describe a general mechanism for reversals, excursions and secular variation. The mechanism happens to keep a memory during the chrons and loose it during the events (excursions and inversions). 相似文献