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1.
Studyonthecharacteristicsofcrust┐mantletransitionzoneinWesternYunnanProvinceHONG-XIANGHU(胡鸿翔)ZHONG-YANGLIN(林中洋)YIN-JUBIAN(边银...  相似文献   

2.
QβstructureofthecrustanduppermantleintheeasternSino┐KoreanparaplatformZHENG-QINHE(何正勤),TAI-LANYE(叶太兰)andWEI-GUOSUN(孙为国)Insti...  相似文献   

3.
Effectsofmagnitudeaccuracyandcomplete┐nesdataonseismichazardparametersHUI-CHENGSHAO(邵辉成),JIA-SHUXIE(谢家树),PINGWANG(王平)andYA-X...  相似文献   

4.
Anapproachondynamicearthquakepredic┐tionbygeoresistivitymeasurementsHONG-KUIZHANG1))(张洪魁),QI-XINGSHEN2)(沈启兴),WEIWU1)(吴卫)YU-L...  相似文献   

5.
Investigationoftheelectricalconductivitybe┐neathChinausinggeomagneticspatialgradi┐entmethodGUO-HUAFAN(范国华)TONG-QIYAO(姚同起)ZUO...  相似文献   

6.
Thefinevelocitystructureofsediment┐base┐mentlayerintheThree┐GorgesRegionoftheChangjiangRiver(YangtzeRiver)HONG-XIANGHU(胡鸿翔),...  相似文献   

7.
Simultaneousinversionofvelocitydistribu┐tionandinterfacepositionsSONG-LINLI1)(李松林)NING-YUANWU2)(吴宁远)ZHAN-LONGSONG1)(宋占隆)JIN-...  相似文献   

8.
Thedeterminationofthebestfitingandtheex┐tremesourcemodelsbyaglobalinversionmethodPENG-CHENGLIU(刘鹏程)andTIAN-YUZHENG(郑天愉)Insti...  相似文献   

9.
Crustalstructureandaccuratehypocenterde┐terminationalongtheLongmenshanfaultzoneZHUZHAO1)(赵珠)JUNFAN1)(范军)SI-HUAZHENG2)(郑斯华)AK...  相似文献   

10.
Anexperimentalstudyontemperaturein┐creasingmechanismofsateliticthermo┐in┐fraredZU-JIQIANG1)(强祖基)LING-CHANGKONG1)(孔令昌)LAN-ZHE...  相似文献   

11.
根据活动断裂分布和区域流变结构建立川滇地区三维有限元模型, 采用上地壳为弹性介质,下地壳和上地幔为Maxwell体的粘弹性模型,模拟川滇地区地壳现今运动和应力分布,探讨川滇地区地壳运动变形的动力学机制. 通过4种不同边界条件和深度分层结构有限元模型的计算结果的对比,认为川滇地区绕喜玛拉雅东构造结顺时针旋转的地壳运动模式主要受川滇地区特殊的边界动力作用控制,川滇菱形块体下地壳流动对上地壳的拖曳作用亦不容忽视. 同时,川滇地区各块体的现今地壳运动场和应力场还受到区域主要活动断裂带的影响, 呈现分块特征.   相似文献   

12.
On the basis of distribution of active fault and regional rheological structure, a three-dimensional finite element model of Sichuan-Yunnan region, China, is constructed to simulate contemporary crustal motion and stress distri- bution and discuss the dynamic mechanism of crustal motion and deformation in the Sichuan-Yunnan region. Lin- ear Maxwell visco-elastic model is applied, which includes the active fault zones, the elastic upper crust and vis- cous lower crust and upper mantle. Four different models with different boundary conditions and deep structure are calculated. Some conclusions are drawn through comparison. Firstly, the crustal rotation about the eastern syntaxis of the Himalaya in the Sicuan-Yunnan region may be controlled by the special dynamic boundary condition. The drag force of the lower-crust on the upper crust is not negligible. At the same time, the main active fault zones play an important role in the contemporary crustal motion and deformation in Sichuan-Yunnan region.  相似文献   

13.
A method for the computation and interpretation of gravity and height changes and vertical gravity gradients produced by magmatic intrusions in a layered elastic–gravitational medium is presented. The methodology assumes a planar medium geometry, which consists of welded layers overlying a half-space. The medium is elastic and gravitating. The intrusion is treated as a point source and can be located at any depth inside the medium. The theoretical elastic–gravitational model allows the computation of the so-called geometric and orthometric vertical displacements as well as gravity changes of different types. The corresponding vertical gravity gradients can also be computed. We present several examples of theoretical computations and study different types of these geometric and orthometric gravity gradients and the information we can get from the application of the methodology described. The results presented show that the use of these gradients is a useful tool to obtain information on the dynamics of the injection processes, including the detection of new magma recharge. We show that using the elastic–gravitational deformation model we can explain non-linear gravity–height relationships that appear in volcanic areas. We also present the application of the methodology to Mayon volcano, Philippines, delineating the intrusion of new magma, consistent with the produced eruptions after the observation period.  相似文献   

14.
Significant changes in the local magnetic field marked the resumption of eruptive activity at Stromboli volcano on February 27, 2007. After differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal thermal noise using temperature data, we identified step-like changes of 1–4 nT coincident with the opening of eruptive fissures in the upper part of the Sciara del Fuoco. The magnetic variations detected at two stations are closely related to the propagation of a shallow NE–SW magmatic intrusion extending beyond the summit craters area. These observations are consistent with those calculated using piezomagnetic models in which stress-induced changes in rock magnetization are produced by the magmatic intrusion. No significant magnetic changes were observed when the first fractures opened along the NE crater rim. Indeed, the stress-induced magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and/or thermal state of the summit area. The continuous long-term decay characterizing the post-eruptive magnetic pattern can be related to a time-dependent relaxation process. A Maxwell rheology was assumed and the temporal evolution of the piezomagnetic field was evaluated. This allowed us to estimate the rheological properties of the medium; in particular, an average viscosity ranging between 1016 and 1017 Pa⋅s was a relaxation time τ of about 38 days.  相似文献   

15.
A three-layer elastic-gravitational fault displacement model using dislocation theory has been developed and used to examine the effect of layering of earth elastic moduli on surface and subsurface displacement fields for a vertical strike-slip fault. The model has been used to examine the effect of depth variation of elastic properties at coseismic and postseismic time scales. For pure strike-slip motion the effect of gravity on coseismic and postseismic horizontal deformation is negligible. For coseismic deformation the model predicts that (for constant Poisson's ratio) an increase in elastic moduli with depth attenuates the displacements within the upper layers with respect to displacement distribution for a uniform half-space, while an inclusion of a soft layer between the top layer and lower half-space amplifies upper layer displacements. The effect of variation in Poisson's ratio on surface and subsurface displacements has also been examined.The effect of postseismic stress relaxation on surface and subsurface displacements for a three-layer model has been calculated and compared with that of a uniformly relaxed half-space model. Layer 1 is assumed to correspond to the upper crust, layer 2 the lower crust and layer 3 the upper mantle. The effect of postseismic stress relaxation within a uniform half-space and within just the lower crust and upper mantle has been examined. Stress relaxation within the whole half-space decreases the amplitude and shortens the wavelength of displacements, while stress relaxation within the lower two layers increases the amplitude and broadens the wavelength of displacements. The difference between uniform and layered postseismic relaxation is particularly pronounced at the base of the crust.Coseismic and postseismic normal and volumetric strains for a vertical strike-slip fault have also been examined. For a uniformly relaxed half-space model, an increase in normal strains is shown with respect to the coseismic elastic solution, whereas the postseismic volumetric strain is effectively zero. For a three-layer model with stress relaxation in the lower layers only, the normal and volumetric strains within the top elastic layer resemble coseismic strains, while in the lower layers which suffer a rigidity decrease, the postseismic volumetric strain is effectively zero.  相似文献   

16.
孟秋  胡才博  石耀霖 《地球物理学报》1954,63(10):3751-3763
挪威北海北部在末次冰期存在较大范围的冰盖,其冰盖的加载和卸载会对地表变形和内部应力调整产生重要影响.本文基于Maxwell黏弹性本构关系,根据初应力法自主开发了一套Maxwell黏弹性体有限元程序,它可以考虑重力和构造加载、地球介质弹性的纵向和横向不均匀性以及黏性的分层性,可以计算冰川载荷变化引起的地球表面变形及内部应力状态的变化.利用它研究了挪威北海北部1.1 Ma以来的冰川载荷变化、特别是两万多年以来冰盖的消退引起的地表冰后回弹.结果表明,自2万年以来,冰后回弹效应在冰盖载荷变化的不同阶段呈现明显的时空变化,现今地表垂直变化速率为几个毫米/年,与观测结果一致.下地壳和上地幔的黏弹性松弛效应明显,上地壳的应力状态在现今海岸线两侧存在差异性,水平和垂直正应力变化可达几十兆帕,剪应力变化有一个先增加后迅速减小至零的过程,与古地震、现今地震时空分布及应力测量结果也比较符合,研究结果有助于加深对冰后回弹的动力学过程的认识.  相似文献   

17.
Investigationontherelationbetweenthegravityanomaly,crustaldeformationandundergroundwaterXue-FangWU(吴雪芳),Shi-HuaTIAN(田世华)andGu...  相似文献   

18.
高锡铭 《地震学报》1984,6(3):304-312
水库蓄水后,水体质量荷载引起地基岩石介质产生静力学形变效应.发生地震的水库,由于震源区岩石介质扩容,也会引起地基岩石介质的形变.本文同时考虑了这两种效应.水体质量荷载的静力学形变总效应包括:荷载引起的地基岩石介质的静态弹性形变,质量引起的重力等位面形变以及静态弹性形变所引起的重力等位面形变.岩石介质扩容效应在一定阶段会引起地基岩石介质的膨胀隆起,这种隆起形变同样也引起重力场变化.采用上述模型分析了丹江水库的水准测量成果,确定了该地区地基岩石介质的 Lame 常数,分析了地面垂直形变与地震的关系,从而认为使用该模型分析蓄水后库区的地面的垂直形变,可以为预报水库区地震提取必要的信息.   相似文献   

19.
张超  赵国光 《地震学报》1981,3(4):399-409
本文对介质变形造成的重力变化作了定量分析, 通过质点位移法(拉格朗日法)导出了介质位移场和由它产生的附加重力场之间的积分关系式.应用已有的弹性和粘弹性半空间任意倾角断层位错的位移表达式, 本文通过三维空间数值积分, 计算了弹性介质和广义开尔文介质中断层不同的运动方式所产生的地表附加重力场, 以及介质流变性导致的重力随时间的变化趋势.参考唐山地震前沧东断裂的活动和震时断层错动, 计算了震前震后相应的重力变化, 其结果与实测重力资料有一定程度的符合.   相似文献   

20.
Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic, elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation and gravity changes depend on such effects.  相似文献   

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