共查询到18条相似文献，搜索用时 140 毫秒
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高精度的GNSS水准及垂线偏差等数据对全面评定重力场模型精度具有重要意义.本文利用美国GSVS2011、GSVS2014项目高精度的GNSS水准及垂线偏差等数据,通过谱组合方法分析了DIR-R5、GOCO05S和TIM-R5等具有代表性的重力场模型的可靠阶次,并分别与EIGEN-6C4形成组合模型DIR-R5-Com、GOCO05S-Com、TIM-R5-Com,在此基础上,进而分析了EGM2008、EIGEN-6C4与3个组合模型的误差特性.实验结果表明:(1)DIR-R5、GOCO05S和TIM-R5模型截断至220阶以前是可靠的;(2)整体上,重力场模型沿经圈走向(GSVS2011)的高程异常和垂线偏差精度要优于沿纬圈走向(GSVS2014)的精度;(3)重力场模型垂线偏差卯酉圈分量的精度要优于子午圈分量的精度;(4)模型高程异常在经圈上的相对精度整体上要优于在纬圈上的精度. 相似文献
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早在三十年前,日本人奥田丰三介绍过日本四国、纪伊地区1946至1949年地方性垂线变化,此结果是由天文观测得到的。在短短几年内,垂线变化最大处达3″.3。将此值换算为重力场水平分量的变化,大约是0.0157伽。大地震前重力异常的最大值一般只能达到数百微伽(指重力仪测得的垂直分量)。前者比后者大数百倍,所以,有人怀疑天文观测的结果。这里有必要对此问题做些讨论。 相似文献
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地表陆地水负荷变化是引起重力场和地壳形变呈现季节性特征的主要因素,并且能够利用地表及空间大地测量技术对其进行有效的监测.本文通过对质量负荷形变效应的理论模拟,描述了水平分量的形变指向以及垂直与水平分量的幅值比可以提高对负荷区域的辨别程度,并且联合GPS坐标时间序列及GRACE模型对喜马拉雅山地区的季节性负荷形变进行了详细对比分析,研究结果显示两者垂直分量的季节性变化具有较好的一致性,且GPS周年项幅值要大于GRACE.而由GRACE解算得到的水平分量结果表明该地区季节性形变主要受东南亚及印度东北部地区的陆地水负荷控制,位于喜马拉雅山地区多数GPS台站的垂直分量及北向分量的初相位与GRACE模型解算结果相近,而部分GPS台站的东向分量与GRACE模型存在明显不同,由此导致GPS与GRACE监测到的形变指向存在差异.通过对GRACE估算精度以及GPS垂直与水平分量幅值比的深入分析,发现GPS对局部周边地区的河流、谷地及农田灌溉等负荷变化造成的形变效应较为敏感,而GRACE由于截断阶次及平滑滤波等影响因素,不仅造成在水平分量上的分辨率远低于垂直分量,而且整体估算精度要低于GPS观测得到的形变信息. 相似文献
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地磁低点位移线两侧异常变化的反相位现象及其解释 总被引：5，自引：2，他引：3
本文通过部分震例研究发现,在地磁低点位移异常日及附近,分布于低点位移线两侧的地磁垂直分量日变化畸变异常部分具有反相位变化特征,而水平分量无类似的现象.作者依据Biot-Savart定律推测,在低点位移异常期间,在低点位移线下方有一引起地磁垂直分量日变化畸变的电流通过,且该电流为线状分布,或仅在垂直面内有分布,埋深一般认为几十千米.作者同时分析认为,当这种电流的分布形成闭合圈或有东西分量时,地磁基本场对其产生的作用力对地震的发生可能有触发作用. 相似文献
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本文具体处理了自1966年以来,周围曾经发生过强震的北京,天津,东京（日本）,水泽（日本）及贝尔格莱德（南斯拉夫）等五个台站的测时测纬数据的残差,发现大震前的三、五个月内测时残差均出现一对符号相反的异常,而测纬残差则是一个孤立的单峰.这种震前的异常特征在无震的年份和无强震台站的资料（为了对比,又选了世界上观测稳定、质量较好的六架照相天顶筒,三架天顶仪和两架等高仪的资料）中极为罕见.对比关系较为密切,难于用偶然误差和其它影响来解释.各地测时与测纬残差异常特征的差异可能系地质构造不同所致.上述结论对进一步探讨地球自转的不均匀性的原因,提高时纬观测精度,揭示地下物质的运动形式及震源机制的本质等方面提供了新的线索和依据. 相似文献
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唐山地震后，北京天文台的研究人员发现了强震前天文测时测纬残差会出现较大异常的现象，随后把这一地震的前兆现象纳入地震预报研究中。1991年起，受国家自然科学基金和地震联合基金的支持，北京天文台组建了天文测震网，此网于1992年底投入试运行，至今已有一年半的时间。天文测震网的主要观测手段是测时、测纬。它的测震原理是这样的：在强震发生前（一般大于5级）几个月，观测仪器的测时、测纬资料将出现较大异常波动，这种波动一般超过两倍中误差，持续时间2－3个月，恢复正常后l一2个月台站附近200km内将会有强震发生。天文测震网现有… 相似文献
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本文对云南天文台Ⅱ型等高仪测纬残差的五日加权均值与云南地区强震的对应关系作了分析,并指出在距该仪器大约400公里以内、6级以上地震的孕震期间,由于地下质量迁移引起银垂线倾斜,从而使天文时纬线残差异常。 相似文献
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洋底板块运动是地球动力学和全球变化研究的重要内容.本文根据质量迁移与地球外部重力场变化的对应关系,利用不同时期测高资料推算的1995—2019全球海洋重力场变化结果,反演分析全球洋底板块运动特征.研究表明,板块汇聚边界、板块内无震海岭、海山群、断裂带等区域重力异常变化显著,而在板块离散边界无明显变化趋势;西南印度洋中脊、大西洋中脊、中印度洋中脊等地区重力异常垂直梯度变化显著,且在西太平洋俯冲带、部分海岭区域也存在明显变化,其空间分布与地形基本吻合.海洋重力场变化整体上准确反映了全球洋底板块构造运动.相较于重力异常变化反演结果,重力垂直梯度的变化能够更为准确地反映洋底板块运动特征,特别是在洋中脊区域,扩张速率越小,垂直重力梯度变化越显著.此外,详细讨论了测高海洋重力场不确定因素对洋底板块运动分析结果的影响,海面坡度改正是主要因素之一. 相似文献
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Total field anomalies as defined from normal aeromagnetic surveys give good approximations of the anomalous components along the direction of the main geomagnetic field, which is generally much larger than the anomalous field. Using the relations between vertical and horizontal components of the field, the total field anomaly is related to any vertical or horizontal component and the corresponding horizontal and vertical derivatives. An example from the Siljan impact structure indicates that such directional filters may be applied to extract useful information from magnetic maps. 相似文献
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First, we present three different definitions of the vertical which relate to (i) astronomical longitude and astronomical
latitude as spherical coordinates in gravity space, (ii) Gauss surface normal coordinates (also called geodetic coordinates)
of type ellipsoidal longitude and ellipsoidal latitude and (iii) Jacobi ellipsoidal coordinates of type spheroidal longitude
and spheroidal latitude in geometry space. Up to terms of second order those vertical deflections agree to each other. Vertical
deflections and gravity disturbances relate to a reference gravity potential. In order to refer the horizontal and vertical
components of the disturbing gravity field to a reference gravity field, which is physically meaningful, we have chosen the
Somigliana-Pizzetti gravity potential as well as its gradient. Second, we give a new closed-form representation of Somigliana-Pizzetti
gravity, accurate to the sub Nano Gal level. Third, we represent the gravitational disturbing potential in terms of Jacobi
ellipsoidal harmonics. As soon as we take reference to a normal potential of Somigliana-Pizzetti type, the ellipsoidal harmonics
of degree/order (0,0), (1,0), (1, − 1), (1,1) and (2,0) are eliminated from the gravitational disturbing potential. Fourth,
we compute in all detail the gradient of the gravitational disturbing potential, in particular in orthonormal ellipsoidal
vector harmonics. Proper weighting functions for orthonormality on the International Reference Ellipsoid are constructed and
tabulated. In this way, we finally arrive at an ellipsoidal harmonic representation of vertical deflections and gravity disturbances.
Fifth, for an ellipsoidal harmonic Gravity Earth Model (SEGEN: http://www.uni-stuttgart.de/gi/research/paper/coefficients/coefficients.zip)
up to degree/order 360/360 we compute the global maps of ellipsoidal vertical deflections and ellipsoidal gravity disturbances
which transfer a great amount of geophysical information in a properly chosen equiareal ellipsoidal map projection. 相似文献
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三峡地区水资源丰富,加上三峡水库蓄放水的影响,水动力环境复杂,对该区域陆地水负荷变化影响的研究还比较薄弱.本文基于CORS站网,辅以少量重力台站数据,采用负荷形变和重力场球谐分析方法,研究了三峡地区陆地水负荷对地壳形变和重力变化的影响.本文研究发现:①基于CORS站网能够监测陆地水负荷引起的地壳形变和地面重力时空变化.②陆地水负荷对垂直形变的影响达厘米级,对水平形变的影响较小,对地面重力的影响可达数百微伽.③2011年1月至2015年6月陆地水负荷对垂直形变影响的年变化趋于平衡,对地面重力变化影响主要集中在三峡水库和重庆市附近.④基于CORS站网确定的三峡地区陆地水地壳垂直形变,与GRACE卫星重力成果在分布规律和趋势上具有较高的一致性,但在部分区域存在差异.本文研究成果可用于水动力环境监测与水资源保护利用,为高程基准和重力基准的动态维护提供支持. 相似文献
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CHARACTERISTICS OF MULTI-SCALE GRAVITY FIELD VARIATION AND SEISMOGENIC MECHANISM ANALYSIS IN THE SOUTHEASTERN TIBETAN PLATEAU 
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下载免费PDF全文 CHEN Zhao-hui MENG Xiao-hong ZHANG Shuang-xi LIU Jin-zhao WANG Tong-qing ZHANG Pin WEI Shao-gang 《地震地质》2019,41(3):690-703
As the most basic geophysical field, the earth gravity field has achieved wide attention, and its spatial anomaly characteristics and dynamic variation can provide important scientific basis for studying the internal structure and dynamics of the Earth. Based on the mobile gravity observation data of the southeastern Tibetan plateau from 2013 to 2016, the dynamic variation tendency and anomaly characteristics of the regional gravity field in different temporal resolutions are obtained before and after the Ludian and Jinggu earthquakes in the study area respectively. The method of wavelet multi-scale decomposition is used to analyze the relationships of gravity field variation with the earth movement, material density change, and strong earthquake preparation. The deep material variation, dynamic process and the mechanism of earthquake inoculation in the southeastern Tibetan plateau are further discussed. Results indicate that the gravity field variation in the source region before the Ludian and Jinggu earthquake respectively is characterized by obvious positive and negative anomalous transition zone and gradient zone that are consistent with the direction of fault tectonics, suggesting the strong crustal movement and mass migration during the earthquake incubation period. The result of wavelet multi-scale decomposition of the gravity field during the period from September 2013 to April 2014 shows that the gravity field variation at different depth and space scale in the crust and upper mantle of the southeastern Tibetan plateau is significantly correlated with seismic distribution and the location of active fault zone. This indicates that the earthquake inoculation in the study area is closely related to the fault movement and the distribution of material density in the crust and upper mantle, which may be affected by the complex deep dynamic process of the material migration in the crust and mantle. The characteristic that strong earthquakes always occur near positive and negative anomaly transition zones and gradient zones of gravity field change is preliminarily explained, based on the dynamic process of material migration in the crust and upper mantle of the southeastern Tibetan plateau. The research results of this paper have some reference value to the study on the earth movement and seismogenic mechanism. 相似文献
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Hydrodynamic pressures and structural response of concrete gravity dams, including dam-reservoir interaction, due to the vertical component of earthquake ground motions are investigated. The response of the dam is approximated by the deformations in the fundamental mode of vibration, and the effects of deformability of bed rock on hydrodynamic pressures are recognized in the analysis. Expressions for the complex frequency response functions for the dam displacement, dam acceleration and lateral hydrodynamic force are derived. These results along with the Fast Fourier Transform algorithm are utilized to compute the time-history of responses of dams of 100, 300 and 600 ft height, with full reservoir, for different values of elastic modulus of mass concrete: 3.0, 3.5, 4.0, 4.5 and 5.0 million psi, to the vertical component of El Centro, 1940, and Taft, 1952, ground motions. It is concluded that the hydrodynamic forces caused by vertical ground motion are affected substantially by damreservoir interaction and depend strongly on the modulus of elasticity of the dam. The dam response to the vertical component of ground motion is compared with that due to the horizontal component. It is concluded that because the vertical component of ground motion causes significant hydrodynamic forces in the horizontal direction on a vertical upstream face, responses to the vertical component of ground motion are of special importance in analysis of concrete gravity dams subjected to earthquakes. 相似文献
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Gravity surveys in western Texas with station spacing of about 400 m were complemented by carefully observed vertical gradients of gravity making use of specially designed and automated instrumentation. The presented areal surveys of 51 and 52 stations taken in relatively flat terrain are parts of a large survey of close to 1000 stations complemented by an equal number of vertical gradient measurements. Quite irregular anomalous vertical gravity gradients surpassing 10 microgal/m were often encountered. Assuming the causative density contrasts to be located not more than 10 m below ground surface then free air correction errors of ± 0.1 mgal and more must be accepted. From a practical point of view there seems to be no other way to control such unpredictable errors than to carefully observe the local variation of vertical gravity gradients with adequate equipment. Making use of very closely spaced gravity measurements to derive these anomalous features seems more costly and cumbersome. 相似文献
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Ｓｐａｔｉａｌａｎｄｔｅｍｐｏｒａｌｖａｒｉａｔｉｏｎｏｆ ｇｒａｖｉｔｙ ｆｉｅｌｄｉｎｔｈｅｃａｐｉｔａｌｒｅｇｉｏｎＣｈａｎｇ－ＣａｉＨＵＡ；（华昌才）ＹｏｎｇＧＵＯ；（果勇）Ｄｕａｎ－ＦａＬＩＵ；（刘瑞法）ＧａｎｇＸＩＡＯ；（肖钢），Ｊ．Ｔ．... 相似文献