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利用玉树震后地质调查获取的地表破裂位移,参考余震精定位结论以及地震波和InSAR反演结果,构建了玉树Ms7.1地震发震断层模型.基于弹性-粘弹分层介质模型中平面矩形位错理论,考虑介质自重的影响,模拟了玉树地震同震形变和重力变化.图像显示,玉树绝对重力点刚好位于同震重力变化极值附近,变化量达到25.02 ×10-8 m·s-2.通过对震前重力变化以及对两台FG-5绝对重力仪的一致性进行讨论,认为实测玉树台27.2 ×10-8 m·s-2为同震重力变化,这与基于位错理论的同震模拟结果一致,是对位错理论近场变化的1次很好的验证. 相似文献
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2010年青海玉树地震及震后青藏高原强震趋势分析 总被引：2，自引：0，他引：2
2010年4月14日青海玉树发生7.1级地震,这是该区历史上发生的最为强烈的地震。该地震属走滑型,地处青藏高原巴颜喀拉地块南边界,发震断裂为甘孜—玉树—风火山左旋走滑断裂,地震破裂主要向震中东南方向。该地震是巴颜喀拉地块与羌塘地块以不同速率向东运动,地块间的差异运动使其边界应力积累到一定程度引发破裂的结果。根据地震定标律估算的主震断层破裂参数和应力参数为:地震矩M0=1.78×1019N.m,矩震级MW=6.8,断层破裂面积S=468km2,断层错距D=1.4m,断层破裂长度L=37km,断层破裂宽度W=12.6km,剪应力τ0=16.8MPa,应力降Δσ=7.03MPa。历史地震分析表明,玉树7.1级地震是在世界8级以上地震、中国西部大三角7.8级以上地震、南北地震带7级以上地震和巴颜喀拉块体7级以上地震处于强烈活动背景下发生的。玉树地震后,青藏高原巴颜喀拉地块、羌塘地块及川滇菱形块体未来发生7级以上地震的危险性较大。 相似文献
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《中国科学:地球科学》2016,(5)
汶川地震发生于巴颜喀拉、华南和川滇菱形块体"三联点"附近,对周边块体和川滇地区主要断裂带也即块体边界带的影响不容忽视.本文基于最新得到的1999~2007、2009~2011和2011~2013年GPS复测结果,利用二维有限元接触模型和"块体加载"方法,模拟强震前后断裂带的运动与受力变化.结果显示汶川地震前龙门山断裂带为低速运动但挤压应力快速积累,汶川地震后巴颜喀拉、滇西南、菱形块体向E-SSE逃逸增强,龙门山断裂带右旋、挤压运动速率和压应力年积累量最高值分别为震前的4.5、2.1和2.5倍.鲜水河南段、安宁河、则木河、大凉山和丽江-小金河断裂带挤压应力快速积累,并形成横跨川滇中部沿NE向展布的挤压应力增强带.鲜水河断裂带中部拉张增强并出现短暂反向.上述变化与该区同期中强地震分布关系密切,揭示出地震活动空间迁移与块体运动变化有关. 相似文献
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鲁甸6.5级地震是川滇菱形块体南南东向运动在青藏高原东缘与华南地块相互作用边界变形带上发生的一次中等强度地震.尽管野外应急科学考察没有发现明显的地震地表破裂带,但云南昭通防震减灾局局域地震台网记录到的余震条带状分布、震后科学考察获得的地震烈度长轴方位和极震区地震裂缝等显示出发震断层为NW向包谷垴-小河断裂,左旋走滑性质,属大凉山断裂南端部组成部分;库仑应力计算表明,鲁甸地震可对周边活动断层系历史地震空段产生应力加载作用,其地震危险性不容忽视. 相似文献
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2022年泸定M6.8地震为近期川滇地区显著强震。本文基于Okubo平面矩形弹性位错理论,采用已有的由地震波反演获得的同震破裂模型,模拟研究了泸定M6.8地震产生的地表同震重力变化、垂直位移和水平位移。结果表明:(1)同震重力变化图像具有以发震断层为界,呈正、负四象限对称分布特征,与震前(2019年9月—2020年9月)实测重力变化图像和发震断层左旋走滑特征具有一致性,说明其孕震过程可用闭锁剪力模型来解释;(2)在远场区域,同震垂直位移图像与重力变化图像类似,位错引起的介质密度变化效应大于地表垂直位移效应,而近场地表垂直位移效应大于介质密度变化效应,显示出负相关性;(3)同震水平位移图像具有对称的四象限特征,与GNSS实测结果显示的变形特性一致。该结果可为地震前后重力、形变观测结果的解释提供依据,同时为强震孕育的机理研究提供线索,尤其为闭锁剪力孕震模式的进一步完善提供了新的实例依据。 相似文献
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《地震地质》2017,(3)
采用分层黏弹模型,考虑了川滇菱形块体东边界1480年以来34个强震和大地震的同震位错和震后黏滞松弛效应,以及各断层段的震间长期构造加载作用,计算了川滇菱形块体东边界18个断层段的断层面上的库仑应力变化随时间的演化。系统地研究了川滇菱形块体东边界鲜水河、安宁河、则木河、小江断裂带间的相互作用,分析断裂带各断层段之间、各断裂带之间先发生的地震对后发生地震的促进或延迟作用,进一步基于断层面上的库仑应力变化计算结果分析各断层段的强震危险性。应力触发的计算结果显示,各断裂带各断层段上先发生的强震可能触发后发生的强震,相邻断裂带上发生的强震之间也可能存在触发作用。各断层段上累积库仑应力变化随时间演化的计算结果显示,鲜水河断裂带的中段及南部磨西段、安宁河断裂带冕宁—西昌段、小江断裂带北部巧家—东川段和南部建水段的库仑应力增加显著,强震危险性值得关注。 相似文献
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川滇地区深浅构造活动强烈、地震发生频度高且强度大.为研究川滇地区断层运动、重力变化和地震活动之间的关系,本文基于连接断层元模型,采用经典弹性半空间位错理论,研究了该地区震间期断层蠕滑引起的重力场变化特征,结果表明:(1)川滇地区韧性层断层蠕滑引起藏东次级块体、雅江次级块体、香格里拉次级块体、滇中次级块体和四川盆地呈现负的空间重力变化,其余块体呈正重力变化;(2)断层蠕滑引起的变形地表重力变化图像与空间重力变化图像形态上相似,量值上较小;(3)川滇地区的强震震中位置,与年际空间重力变化的零值区有一定的对应关系. 相似文献
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D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2010,46(7):613-623
The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The
times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized
by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and
the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between
the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic
world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by
the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle
of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes
in the organic world. 相似文献
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The developed dynamic model of the main geomagnetic field (MGF) includes the sources of three levels, which have existed and continuously changed during the 100-year period. The spatial-temporal dynamics of the secular variations in MGF has been considered based on this model. It has been indicated that, at different times, the formation of anomalies (located in similar regions) depended on the total dynamics of different combinations of sources, including a change in the parameters of the dipoles of the secondorder smallness. Anomalies generated by the dynamics of the dipoles of the third-order smallness do not evidently manifest themselves in the total secular variations but are responsible for the specific shapes of isodynamic lines. Based on the stability and continuity of the constructed model, the conclusion is made that long-living turbulent flows of different scales can exist in the liquid core. 相似文献
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Yu. F. Moroz T. A. Moroz V. A. Loginov A. G. Nurmukhamedov D. A. Alekseev 《Izvestiya Physics of the Solid Earth》2016,52(1):29-44
The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids. 相似文献
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M. MONIRUL QADER MIRZA 《水文科学杂志》2013,58(5):613-631
Abstract The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly. 相似文献
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In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January. 相似文献
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The continuous increase in concentration of greenhouse gases in the atmosphere is expected to cool higher levels of the atmosphere. There is some direct and indirect experimental evidence of long-term trends in temperature and other parameters in the mesosphere and lower thermosphere (MLT). Here we look for long-term trends in the annual and semiannual variations of the radio wave absorption in the lower ionosphere, which corresponds to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency to a positive trend in the amplitude of the semiannual wave appears to be observed. The reality of a similar tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of the annual wave is probably induced by the trend in the yearly average values of absorption. The phases of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time in the year. A tentative interpretation of these results in terms of changes of the seasonal variation of temperature and wind at MLT heights does not contradict the trends observed in those parameters. 相似文献
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George E. Backus 《Physics of the Earth and Planetary Interiors》1982,28(3):191-214
A rigorous singular perturbation theory is developed to estimate the electric field E produced in the mantle M by the core dynamo when the electrical conductivity σ in M depends only on radius r, and when |r?rln σ| ? 1 in most of M. It is assumed that σ has only one local minimum in M, either (a) at the Earth's surface ?V, or (b) at a radius b inside the mantle, or (c) at the core-mantle boundary ?K. In all three cases, the region where σ is no more than e times its minimum value constitutes a thin critical layer; in case (a), the radial electric field Er ≈ 0 there, while in cases (b) and (c), Er is very large there. Outside the critical layer, Er ≈ 0 in all three cases. In no case is the tangential electric field ES small, nearly toroidal, or nearly calculable from the magnetic vector potential A as ??tAS. The defects in Muth's (1979) argument which led him to contrary conclusions are identified. Benton (1979) cited Muth's work to argue that the core-fluid velocity u just below ?K can be estimated from measurements on ?V of the magnetic field B and its time derivative . A simple model for westward drift is discussed which shows that Benton's conclusion is also wrong.In case (a), it is shown that knowledge of σ in M is unnecessary for estimating ES on ?K with a relative error |r?r 1nσ|?1from measurements of ES on ?V and knowledge of ?tB in M (calculable from ?tB on ?V if σ is small). Then, in case (a), u just below ?K can be estimated as . The method is impractical unless the contribution to ES on ?V from ocean currents can be removed.The perturbation theory appropriate when σ in M is small is considered briefly; smallness of σ and of |r?r ln σ|?1 a independent questions. It is found that as σ → 0, B approaches the vacuum field in M but E does not; the explanation lies in the hydromagnetic approximation, which is certainly valid in M but fails as σ → 0. It is also found that the singular perturbation theory for |r?r ln σ|?1 is a useful tool in the perturbation calculations for σ when both σ and |r?r ln σ|?1 are small. 相似文献
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Yu. V. Balabin A. V. Germanenko B. B. Gvozdevsky E. V. Vashenyuk 《Geomagnetism and Aeronomy》2014,54(3):347-356
X-ray intensity variations in the surface layer of the atmosphere during precipitation in Apatity and Spitsbergen were analyzed. Based on a comprehensive system of monitoring over the radiation background, X-ray radiation variations were detected. These variations were found to be associated with meteorological processes in the lower atmosphere. X-ray energy spectra were obtained under good weather and precipitation conditions. These spectra have no characteristic lines inherent to radionuclides. Additional studies make it possible to suggest that the growth in X-ray radiation during precipitation is mainly caused by braking radiation of energetic electrons additionally accelerated by electric fields in rain clouds. 相似文献
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Site response in the Qionghai Basin in the Wenchuan earthquake 总被引：2，自引：1，他引：1
Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations (i.e., one on bedrock and three on soil) in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations (PGAs) on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96–6.58, 6.27–10.98, and 3.17–6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites. 相似文献
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Variations in the Caspian Sea Level in the Historic Epoch 总被引：1，自引：0，他引：1
Reconstruction of variations in the Caspian Sea level is proposed based on the results of investigations of deposits in the Agrakhan sand bar and bays (or former bays) of the eastern sea coast. The history of sedimentation in particular regions is reconstructed by the radiocarbon dating. Generalized data on the age of deposits are used to construct the most likely temporal course of variations in the sea level within the historic epoch. 相似文献