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1.
Influence of soil consolidation and thermal expansion effects on height and gravity variations 总被引：2，自引：0，他引：2
C. Romagnoli S. Zerbini L. Lago B. Richter D. Simon F. Domenichini C. Elmi M. Ghirotti 《Journal of Geodynamics》2003,35(4-5):521-539
The daily GPS height series of the Medicina station were analyzed for the period July 1996–September 2001. The station is located in the middle Po Plain on fine-grained alluvial deposits. A seasonal oscillation in the order of 18 mm (peak-to-peak amplitude) is present in the data. This crustal deformation has been modeled by including variations in the atmospheric, oceanic and hydrologic mass. The vertical positions can also be affected significantly by soil consolidation. Geotechnical parameters derived by in situ tests and laboratory analyses of the clayey soil collected at Medicina allowed the estimate of the soil settlement relevant to the seasonal oscillation of the surficial water table. Thermal expansion of the geodetic monument has to be taken into account in the case of high-precision vertical positioning. In this work models both for the soil consolidation and the thermal expansion effects are provided. The continuous gravity observations collected at Medicina by means of a superconducting gravimeter also exhibit a marked seasonal oscillation, which has been interpreted as the sum of loading and Newtonian attraction effects, as well as of the contribution due to soil consolidation. Especially the study concerning the soil consolidation effect has allowed a better insight on the seasonal vertical movements occurring at the Medicina station by providing quantitative information on soil behavior due to change of effective pressures. The results can be applied to those stations characterized by similar fine-grained soils and surficial hydrogeology. 相似文献
2.
This work describes a study of GPS heights, gravity and hydrological time series collected by stations located in northeastern Italy. During the last 12 years, changes in the long-term behaviors of the GPS heights and gravity time series are observed. In particular, starting in 2004–2005, a height increase is observed over the whole area. The temporal and spatial variability of these parameters has been studied as well as those of key hydrological variables, namely precipitation, hydrological balance and water table by using the Empirical Orthogonal Functions (EOF) analysis. The coupled variability between the GPS heights and the hydrological balance and precipitation data has been investigated by means of the Singular Value Decomposition (SVD) approach. Significant common patterns in the spatial and temporal variability of these parameters have been recognized. In particular, hydrology-induced variations are clearly observable starting in 2002–2003 in the southern part of the Po Plain for the longest time series, and from 2004–2005 over the whole area. These findings, obtained by means of purely mathematical approaches, are supported by sound physical interpretation suggesting that the climate-related fluctuations in the regional/local hydrological regime are one of the main contributors to the observed variations. A regional scale signal has been identified in the GPS station heights; it is characterized by the opposite behavior of the southern and northern stations in response to the hydrological forcing. At Medicina, in the southern Po Plain, the EOF analysis has shown a marked common signal between the GPS heights and the Superconducting Gravimeter (SG) data both over the long and the short period. 相似文献
3.
GPS技术能以高空间和高时间分辨率监测地表形变.但由于测量原理的不同,GPS监测的地表形变与GRACE存在差异.本文比较了ITRF2008-GPS残差序列与基于CSR的RL05版本的GRACE球谐系数的地表形变序列的差异.结果表明,GPS和GRACE的周年变化在高程方向上具有较好的一致性,但水平方向的差异明显.重点分析了影响GPS/GRACE地表形变差异(尤其是水平方向)的三个因素:不同GPS站时间序列间的不确定性,热弹性形变和区域形变.GPS站地表形变本身的不确定度在一定程度上导致了GPS/GRACE间的差异(特别是水平方向).结合热弹性形变理论指出,由温度变化引起的热弹性形变也是导致GPS/GRACE的南北方向差异的主要原因之一.因此利用GPS数据研究地表质量负载时,必须消除热弹性形变的影响.区域负载对GPS/GRACE水平方向差异的影响也是不可忽略的,特别是对欧洲区域. 相似文献
4.
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
5.
《Journal of Geodynamics》2010,49(3-5):166-171
The gravimetric time series achieved from the combination of superconducting and absolute gravimeters are characterized by highest precision and long-term stability. If the effects of Earth and ocean tides, atmosphere and polar motion are removed, the residual curve is dominated by hydrological mass variations. A major source of these variations is water storage changes in the vicinity of the sensor. However, global variations contribute to the signal significantly. For three stations of superconducting gravimeters, a comparison of the principal components obtained from the residual gravity curve on the one hand and continental water storage from the WaterGAP Global Hydrological Model (WGHM) on the other hand is carried out. The results demonstrate a coherence of seasonal variations but a difference in the contribution of the local zone at the individual stations, which point out the need for a careful and site-specific examination of local effects. 相似文献
6.
利用GRACE卫星重力资料,计算了中国大陆及周边的卫星重力时变场和地表密度变化分布,获取了具有代表性的点位区域的每月重力变化时间序列.同时获得了WUSH、LHAS、KUNM、LUZH站相对于区域参考框架的GPS位移时间序列.卫星重力观测结果显示喜马拉雅弧形带的重力在2004年苏门答腊Mw9.3地震后快速下降, 2006~2008年尤为明显,西域地块西北边界带上震后重力下降也较为显著;而沿青藏高原北至东边界2007年出现明显的重力上升沿构造边界的弧形分布,且2008年南北地震带中南段重力上升变化显著.这些苏门答腊地震后的重力变化趋势到汶川地震发生后才开始改变.GPS位移结果显示四个台站均记录到苏门答腊大地震的同震信号,震后WUSH、LHAS、KUNM站水平位移向量出现明显的运动趋势改变,且一直持续到2008年汶川Ms8.0地震的发生.GRACE卫星揭示的青藏高原及周边地表质量的变化为解释汶川地震的动力机制提供了新的观测途径和资料.本文结合区域构造运动的特点和GPS位移,对GRACE观测的时变重力场特征及汶川地震的动力机制进行了初步解释和讨论. 相似文献
7.
Petra Döll Mathias Fritsche Annette Eicker Hannes Müller Schmied 《Surveys in Geophysics》2014,35(6):1311-1331
Better quantification of continental water storage variations is expected to improve our understanding of water flows, including evapotranspiration, runoff and river discharge as well as human water abstractions. For the first time, total water storage (TWS) on the land area of the globe as computed by the global water model WaterGAP (Water Global Assessment and Prognosis) was compared to both gravity recovery and climate experiment (GRACE) and global positioning system (GPS) observations. The GRACE satellites sense the effect of TWS on the dynamic gravity field of the Earth. GPS reference points are displaced due to crustal deformation caused by time-varying TWS. Unfortunately, the worldwide coverage of the GPS tracking network is irregular, while GRACE provides global coverage albeit with low spatial resolution. Detrended TWS time series were analyzed by determining scaling factors for mean annual amplitude (f GRACE) and time series of monthly TWS (f GPS). Both GRACE and GPS indicate that WaterGAP underestimates seasonal variations of TWS on most of the land area of the globe. In addition, seasonal maximum TWS occurs 1 month earlier according to WaterGAP than according to GRACE on most land areas. While WaterGAP TWS is sensitive to the applied climate input data, none of the two data sets result in a clearly better fit to the observations. Due to the low number of GPS sites, GPS observations are less useful for validating global hydrological models than GRACE observations, but they serve to support the validity of GRACE TWS as observational target for hydrological modeling. For unknown reasons, WaterGAP appears to fit better to GPS than to GRACE. Both GPS and GRACE data, however, are rather uncertain due to a number of reasons, in particular in dry regions. It is not possible to benefit from either GPS or GRACE observations to monitor and quantify human water abstractions if only detrended (seasonal) TWS variations are considered. Regarding GRACE, this is mainly caused by the attenuation of the TWS differences between water abstraction variants due to the filtering required for GRACE TWS. Regarding GPS, station density is too low. Only if water abstractions lead to long-term changes in TWS by depletion or restoration of water storage in groundwater or large surface water bodies, GRACE may be used to support the quantification of human water abstractions. 相似文献
8.
连续重力观测和GPS的技术结合能够监测到物质迁移和地壳垂直形变之间的量化关系.和相对重力测量以及绝对重力测量技术相比,其避免了时间分辨率和观测精度低,无法精细描述观测周期内的物质迁移过程问题.本文利用武汉九峰地震台超导重力仪SGC053超过13000 h连续重力观测数据;同址观测的绝对重力仪观测结果;气压数据;周边GPS观测结果;GRACE卫星的时变重力场;全球水储量模型等资料,采用同址观测技术、调和分析法、相关分析方法在扣除九峰地震台潮汐、气压、极移和仪器漂移的基础上,利用重力残差时间序列和GPS垂直位移研究物质迁移和地壳垂直形变之间的量化关系.结果表明:在改正连续重力观测数据的潮汐、气压、极移的影响后,不仅准确观测到2009年的夏秋两季由于水负荷引起的约(6~8)×10-8m·s-2短期的重力变化.而且在扣除2.18×10-8(m·s-2)/a仪器漂移和水负荷的影响后,验证了本地区长短趋势垂直形变和重力变化之间具有一致的负相关性规律.同时长趋势表明该地区地壳处于下沉,重力处于增大过程,增加速率约为1.79×10-8(m·s-2)/a.武汉地区重力梯度关系约为-354×10-8(m·s-2)/m. 相似文献
9.
Analysis of seasonal signals and long-term trends in the height time series of IGS sites in China 总被引：1，自引：0，他引：1
The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are performed on the raw GPS time-series data developed by the Scripps Orbit and Permanent Array Center (SOPAC). The seasonal-trend decomposition procedure based on LOESS (STL) is utilized to extract precise seasonal signals, followed by an estimation of the long-term trend with the application of maximum likelihood estimation (MLE) to the seasonally adjusted time series. The Up-components of all sites are featured by obvious seasonal variations, with significant phase and amplitude modulation on some sites. After Kendall’s tau test, a significant trend (99% confidence interval) for all sites is achieved. Furthermore, the trends at sites TCMS and TNML have significant changes at epochs 2009.5384 and 2009.1493 (95% confidence interval), respectively, using the Breaks For Additive Seasonal and Trend test. Finally, the velocities and their uncertainties for all sites are estimated using MLE with the white noise plus flicker noise model. And the results are analyzed and compared with those announced by SOPAC. The results obtained in this paper have a higher precision than the SOPAC results. 相似文献
10.
局部Slepian函数是将局部区域内的地球物理信号转化为空间谱的一种方法,其可以保证在球面上局部范围内获得最优谱平滑解,非常适用于局部范围地球物理信号的研究.本文利用中国陆态网西南地区72个测站的连续GPS观测资料分析川云渝地区陆地水负荷形变特征,并基于Slepian函数方法解算60阶的空间谱基函数,结合弹性质量负荷理论研究了川云渝地区2011年至2015年陆地水储量变化的时空分布模式.针对Slepian函数的边界效应问题,本文使用GLDAS格网数据计算得到站点处垂直负荷位移时间序列,然后利用该位移数据来进行水储量变化恢复实验,结果表明当边界扩充为3°时能较好地恢复GLDAS模型输出的陆地水储量变化.通过对比区域内GPS、GRACE、GLDAS得到的等效水高以及降雨数据,发现季节性降水是陆地水变化的一个重要驱动因子,GPS反演结果与GRACE和GLDAS数据具有较强的空间一致性.云南地区周年变化要强于川渝地区,其中云南西部的山区陆地水变化最大,约为30 cm,最小为川北以及重庆地区仅为7 cm.相较于GPS反演结果,GRACE与GLDAS明显低估了陆地水储量的季节性变化,分别达到24%和47%.比较分析地区内平均等效水高时间序列的相位发现,GPS得到的陆地水变化与降雨数据一致性较好,而GRACE与GLDAS存在一到两个月左右的时延.同时GPS能较好的探测出2015年1月左右南方地区大范围的强降水,而GRACE与GLDAS并没有体现出该现象,说明GPS能更为灵敏地探测到局部地区陆地水的变化.在站点等效水高时间序列上,GPS与GRACE的相关性总体上要优于GPS与GLDAS,陆地水周年变化较大的云南和四川西部地区站点三种数据间相关性较好,而其他季节性信号不明显的地区则相关性较差.本文的研究表明运用GPS-Slepian方法能够独立地监测高时空分辨率的陆地水储量变化,是作为当前补充GRACE观测资料空缺期的有益尝试. 相似文献
11.
利用GRACE重力卫星观测资料,获得了日本MW 9.0地震前的区域重力变化;获取了TSKB、DAEJ、SUIY和HLAR站GPS连续观测垂直位移。地震前区域重力变化主要经历2个过程：1）2002年8月至2007或2008年底的先上升后下降的小幅变化过程,该过程可用二次多项式拟合;2）第1个过程后的重力快速上升后下降的较大幅度变化。2008年黑龙江至乌苏里区域重力下降明显,2009年和2010年在太平洋俯冲带的广大区域重力呈显著上升,并且正、负重力变化区域都向SW方向迁移。2010年与2009年相比,重力变化沿板块边界带呈东、西部分的正、负分布特征;东部区域点位2010年初开始重力快速下降至地震发生;而西部点位在此期间仍然为重力正变化高值,地震发生后开始下降变化。远场GPS垂直位移具有2006年中开始的隆升变化,2009年初开始转向。经过与GLDAS陆地水储量改变引起的重力变化比较,认为区域重力变化主要由地表水储量改变引起。但位于海洋侧的P01和P03位置类似下降变化也非常明显,这表明区域重力的异常变化很可能与地下深部的地幔物质运移和热引起的区域气候改变有关。这种异常变化特征与地震孕育的关系有待今后深入研究。 相似文献
12.
13.
Influence of stratospheric ozone changes on long-term trends in the meso- and lower thermosphere 总被引：2，自引：2，他引：0
As predicted by model calculations, long-term changes in the stratospheric ozone content should influence trends in the meso- and thermosphere also. These predictions have been tested by means of ionospheric reflection height data in the low-frequency (LF) range and critical frequency data series of the ionospheric E layer, foE, observed at different stations around the world. It was shown that an essential part of the derived trends in the mesosphere and in the lower thermosphere is correlated with long-term changes of the atmospheric ozone content. During the sub-interval with the strongest ozone decrease (1979–1995) the detected ionospheric trends are most pronounced. Additionally was also demonstrated that the longitudinally dependent ozone trends are related to similar variations in the foE trends. 相似文献
14.
The geodynamic interpretation of the results of GPS observations among the permanently operating stations which establish the frame for defining and conserving the coordinate system and simultaneously for describing the fundamental tendencies of dynamics in the area represented by them, should be deprived of the effects of geodynamic phenomena, which can be either periodic or short-term (even non-periodic) so that secular changes may be found. Some of these influences are included in scientific processing software, others have to be modelled later. The purpose of this project is to determine the influences of the indirect effect of ocean tides and the direct deformational effect of the atmosphere on the results of GPS observations, performed at stations Pecný (Czech Republic), Wettzell (FRG) and Graz (Austria), and also for the GPS stations of the Central Europe Regional Geodynamic Project (CERGOP) in the region of Central and East Europe. On the basis of analyses and results it is possible to claim that at the present accuracy of GPS observations the influence of ocean loading and atmospheric pressure effects for geodynamic campaigns in the region of the Czech Republic is negligible. For campaigns in larger regions (i.e. Central Europe) atmospheric corrections will have to be applied to height differences. These corrections, however, due to their periodicity have negligible influence on secular changes. 相似文献
15.
卫星重力和GPS测量技术可以监测地表流体(大气、海洋和陆地水)质量季节性迁移引起的地表周年形变;与陆地水等地表流体模型综合模拟的地表形变相比,卫星重力的形变监测结果避免了模型的精度不确定性带来的误差.本文利用前60阶GRACE卫星时变重力资料和“去相关”、组合滤波两类滤波方法分别解算了中国及邻区的地表季节性垂直形变,并与区内42个GPS台站上观测到的季节性信号进行了比较,发现采用“去相关”滤波方法处理后的结果优于采用组合滤波处理后的结果.文中采用“去相关”滤波方法,GRACE解算的周年垂直形变的振幅、相位和GPS结果总体上一致;少数站上GRACE和GPS得到的振幅或相位相差较大,主要因素可能与GPS解算策略、GPS观测资料的连续性或局部大气、水文过程等地球物理因素有关.在中国及邻区的陆地上GRACE解算的周年垂直形变的振幅最小值出现在TASH台站东南,约1×10-3 m;最大值出现在恒河-澜沧江流域,可达10×10-3 m.文中的结果证实了在中国及邻区可以用GRACE卫星重力这种新手段监测大尺度的地表周年垂直形变. 相似文献
16.
本文利用卫星重力、卫星测高和海洋温盐数据反演计算全球海水质量变化,并分析其时空变化特征.卫星重力数据利用2003年1月~2006年12月的GRACE月时变重力场球谐系数,同时考虑替换一阶项和C20项,并进行了相关误差滤波、高斯滤波和陆地水文信号泄漏改正,计算得到海洋等效水高变化;利用相同时间跨度的卫星测高数据和海洋温度、盐度水文观测数据,计算全球海平面变化和比容海平面变化,反演得到海水质量变化.反演的两种海水质量变化的年际变化特征一致性较好.三种数据得到的长期趋势变化,与1993~2003年的结果相比,可以看出,海水质量变化加速,并已成为全球海平面上升的主要因素. 相似文献
17.
新疆地区GPS区域站1999—2007年、 2009—2011年观测资料分析结果表明, 该地区水平运动速率分区性明显; 2011年6月以来该地区中强地震增强. 该文在分析区域站水平运动速率特征的基础上, 对2011年1月—2012年3月20个GPS连续观测站基线变化时间序列进行了分析. 结果表明, 各观测站坐标变化量在2011年4月后整体上变大, 新疆地区地壳运动增强, 但具体到不同的山区和盆地, 基线变化趋势各异． 其中, 塔里木盆地和准噶尔盆地内部变形相对较小, 主要变化发生在天山中南部, 出现明显的南北向挤压缩短． 相似文献
18.
《Journal of Geodynamics》2010,49(3-5):354-359
In order to achieve a consistent combination of terrestrial and satellite-derived (GRACE) gravity field variations reductions of systematic perturbations must be applied to both data sets. At the same time evidence needs to be provided that these reductions are both necessary and sufficient. Based on the OMCT and the ECCO model the gravity effect of non-tidal oceanic mass shifts is computed for various sites equipped with a superconducting gravimeter (SG) and esp. the long-periodic contributions are studied. With these oceanic models the dynamic ocean response to atmospheric pressure loading is automatically computed, and thus goes beyond the more simplistic concepts of an inverted barometer, or alternately a rigid ocean, which is a clear advantage.The findings so far are ambiguous: for instance the systematic seasonal change of about 10 nm/s2 in gravity for mid-European stations is presently not found in the observed gravity variations. Generally, the order of magnitude of the total effect of 22–27 nm/s2 is surprisingly large for inland stations. In some data sections the reduction leads to the removal of some of the larger residuals. The results obtained for the South-African station Sutherland differ. Here the modelled seasonal variation caused by the non-tidal oceanic mass redistribution and gravity residuals generally correlate, and thus by the reduction an improvement of the signal-to-noise ratio in the gravity observations is achieved.An explanation for the different results might be found in the global hydrological models. Such a model is needed in order to remove the effect of large-scale variations in continental water storage in the gravity observations. This reduction plays a greater role for European stations than for the South African site. A critical impact of the land-sea-mask used in the oceanic models and the subsequent insufficient resolution of the North and Baltic Sea on the computations at the mid-European sites could not be confirmed.From a comparison between the OMCT and the ECCO model substantial discrepancies in some regions of the earth emerge, while both predict variations at inland stations in Europe, South Africa, and Asia of similar magnitude. We currently hesitate to recommend including this reduction in the routine processing of SG data because the seasonal order of magnitude for inland stations is unexpectedly large and partly significant deviations between the modelled oceanic effects exist. If the order of magnitude proves to be correct universally, this reduction has to be applied. 相似文献
19.
1 Introduction Large-scale mass redistribution, or temporal varia- tion of mass within the Earth system, the driving force of interactions between solid Earth and geophysical fluids envelope (i.e., atmosphere, ocean, and hydro- sphere), is an important geophysical process critical to human life. Most of the interactions between solid Earth and the atmosphere/oceans happen at seasonal and inter-annual time scales. One important contribu- tor of mass redistribution at seasonal and inter-annual … 相似文献
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《Journal of Geodynamics》2010,49(3-5):325-330
The network of superconducting gravimeters (SG) of the ‘Global Geodynamics Project’ (GGP) offers the unique opportunity to supplement and validate the gravity field variations derived from the GRACE satellite mission. Because of the different spatial and temporal resolutions of the gravity data a combination of all datasets can be used to retrieve a maximum of information regarding mass transfers especially related to hydrology which is deployable as constraint for hydrological modelling.For a consistent combination of the datasets the gap between terrestrial data of superconducting and absolute gravimeters (AG) and from satellite data has to be bridged. A successful combination of SG and AG data could be realized for several stations which resulted in time series of the highest accuracy and long-term stability.In principle, the same reductions applied to GRACE data have to be taken into account for the terrestrial data. The separation of local hydrological effects in SG observations is crucial for the comparison with satellite-derived gravity data. It is shown that even for stations with a hydrological challenging situation such as Moxa/Germany local hydrology-induced effects can be successfully modelled.Currently, the study focuses on Europe with its dense and long-term observation network. Regarding the consistency of the SG gravity variations they are representative for a larger region. From a comparison with GRACE-derived gravity field changes, and the variations due to hydrological models a principle good agreement emerges. 相似文献