基于MERIS水汽数据的ASAR干涉图改正

水汽延迟是InSAR技术的重要误差源,已成为高精度差分干涉测量的主要限制.本文比较分析了GPS与MERIS可降水量反演结果以及水汽变化量探测结果,研究发现两者探测到的水汽含量和水汽变化量均存在较好一致性.在此基础上,以南加州地区为例验证了差分MERIS PWV用于同步ASAR干涉图水汽改正的可行性,经过水汽改正干涉图质量提高了约23%,并进一步对比了InSAR形变监测结果与GPS探测到的形变,比较结果表明,消除水汽影响后干涉图形变结果可靠性提高了19%.     

InSAR大气误差改正及其在活动断层形变监测中的应用

为了获取青藏高原东北缘老虎山断裂带精确的震间形变速率场,通过对短时间基线干涉图大气改正效果的评价,从3种外部大气数据(MERIS, ERA-Ⅰ, WRF)中确定出最优的大气改正方法,用于长时间基线干涉图中的大气信号改正;然后利用层叠法(stacking)累积平均经大气和轨道改正后的干涉图,获取了研究区的震间形变速率场.结果显示:海原断裂系统区域内,MERIS和ERA-Ⅰ的大气改正效果优于WRF;MERIS和ERA-Ⅰ的改正结果给出了相似的形变速率场,断层两盘相对形变速率为视线向2.5 mm/a,转换成平行于断层方向为6.5 mm/a,与GPS结果一致;在近断层5 km的范围内,出现了较大的形变梯度,揭示了浅层蠕滑的存在.      

基于GPS和MODIS的ENVISAT ASAR数据干涉测量中大气改正方法研究

GPS数据用于改正InSAR中大气延迟误差的方法受GPS站点密度的限制,只利用有限的几个站点所观测到的大气数据来生成干涉图的大气改正图,往往达不到很好的效果.本文研究利用GPS与MODIS数据的联合使用来生成大气改正图,首先用GPS数据对MODIS水汽产品进行分块校准,并且对MODIS水汽数据进行了空间结构函数分析,得到研究区域内水汽场的空间分布规律.然后把这种区域水汽场的空间分布信息结合到Kriging内插法中生成更为合理的水汽图.通过上海地区ENVISAT ASAR数据的实验发现,这种加以改正的GPS和MODIS数据联合改正法不仅可以对长波大气信号有明显的消弱,还能消弱一些短波的大气信号,特别是一些幅度较强的短波信号;经过GPS+MODIS算法改正后,短波信号占优和长波信号占优的两幅差分大气延迟图的整体RMS分别降低了32.74%和38.82%,去除幅度较大.与GPS+ATM(大气传输模型)算法比较,我们发现,在上海地区有限的数据条件下（即研究区域内只有6个GPS点）,GPS+MODIS法在大气去除效果或者说大气信号重现能力方面优于GPS+ATM算法.GPS+MODIS算法在捕获短波大气信号方面要比GPS+ATM更有优势,因此也可以改正短波大气误差.     

利用NOAA_16/FY_1C和ASAR数据纠正大气水汽对重轨星载D_INSAR的影响

大气水汽影响一直是造成重轨星载合成孔径雷达差分干涉测量监测结果不确定性的一个重要因素.本文以地表形变速率稳定的延怀盆地为试验区，利用ASAR数据得到该区域的差分干涉处理结果，利用与ASAR数据获取时间相近的NOAA_16/FY_1C数据对该区域的大气水汽含量进行了反演.通过这些结果，对差分干涉处理结果中大气水汽的影响进行了去除.去除大气水汽影响后得到的地表形变结果与野外考察实测结果基本吻合，从而验证了该方法的可行性.     

基于GPS和大气传输模型的InSAR大气改正方法研究

利用GPS数据改正InSAR大气影响中,GPS站网的低空间密度是限制改正精度的一个主要因素.文中引入大气传输模型（ATM）来考虑大气状态在时间上的演化,并兼顾了风向的估计,把GPS-ZWD（GPS湿延迟）时间序列观测值转换为空间上分布比较稠密的GPS-ZWD网络,然后利用该稠密网络在空间上内插产生水汽延迟图,来更好地模拟InSAR影像获取时刻的水汽场,提高大气改正精度.实验结果表明,在研究地区有限的数据条件下（即只有6个GPS点的情况下）,GPS+ATM算法在重现大气信号能力方面比单纯的使用影像获取时刻的GPS-ZWD数据要强,并且其对长波的大气误差去除更明显;用来做实验的三幅差分干涉图中,GPS+ATM算法对两幅以长波信号为主的干涉图中的大气影响分别降低了21.7%和22.6%,比仅使用SAR过境时刻GPS-ZWD数据时的结果分别改进了4.5%和8.7%.而对以短波信号为主的干涉图没有明显提高.     

基于全球气象再分析资料的InSAR对流层延迟改正研究

气压、温度和水汽含量等大气物理参数的时空变化导致的对流层延迟是制约合成孔径雷达干涉测量(Interferometric Synthetic Aperture Radar,InSAR)高精度应用的重要因素之一.最新研究显示气象再分析资料在补偿对流层延迟影响方面具有巨大的应用潜力,这促使我们对其有效性和鲁棒性做进一步的研究和探索.本文首先推导了利用气象再分析资料对InSAR进行对流层延迟校正的算法;然后以美国南加州地区的ENVISAT ASAR数据为例,分析了基于两种气象再分析资料(ERA-Interim和North American Regional Reanalysis,NARR)校正InSAR对流层延迟改正的效果;通过与MERIS水汽延迟改正结果比较,验证了该方法的有效性.实验结果表明:(1)不能简单忽略干延迟,可通过气象再分析资料进行有效估计;(2)通过与MERIS水汽产品获得的对流层延迟比较发现,气象再分析资料能够取得接近于MERIS的改善效果;(3)对ERA-Interim和NARR两种气象再分析资料而言,虽然后者具有更高的时间和空间分辨率,但在改正InSAR对流层延迟方面并没有表现出比前者更明显的优势;(4)气象再分析资料可以很好地估计与地形强相关的垂直分层延迟,但对于小尺度的湍流混合延迟的捕捉能力有限.综合分析认为,气象再分析资料的优势在于其数据可随时获得、免费和全球覆盖,它可以显著减弱大尺度的垂直分层延迟对干涉图相位的影响,从而有助于InSAR获取更真实可靠的地形高程和地表形变信息.     

利用Envisat ASAR数据探讨渭河盆地断层现今的滑动速率

与板块边界的断层相比,块体内部的断层滑动速率较小,但仍具备发生大地震的潜力。渭河盆地历史上曾多次发生大地震,而盆地内一系列正断层长期的滑动速率却相对较低。文中以渭河盆地中部的口镇-关山断裂、渭河断裂和北秦岭断裂为例,利用合成孔径雷达干涉测量技术(InSAR)对盆地内断层现今的滑动速率进行研究和分析。搜集了欧洲空间局Envisat卫星161号降轨2003—2010年的32幅影像数据,通过ROI_PAC软件对渭河盆地的Envisat ASAR数据进行处理,得到98幅空间基线长度≤300m的干涉图,并从中挑选出质量较好的33幅干涉图用于后续的时序分析。使用π-RATE对33幅干涉图创建最小生成树网络(MST)并进行轨道误差校正、与地形相关的大气校正、去除参考相位和计算协方差矩阵等,获得渭河盆地中部3条主要断裂在7a内的平均滑动速率。结果显示,2003—2010年期间渭河盆地断裂的滑动速率较小,不超过2mm/a,其中口镇-关山断裂没有明显的形变信号,渭河断裂有约1mm/a的卫星视线向形变;西安市整体地表沉降速率在垂向上最大可达10mm/a。文中以稳定的鄂尔多斯地块为参考评估In SAR时序分析的精度,得到In SAR速率图的误差约为(-0. 1±1) mm/a,证明了结果的可靠性。文中工作可为获取断层10a尺度的现今滑动速率提供重要的技术思路,继而为评估地震危险性以及危害性预测提供参考依据。     

一种InSAR大气相位建模与估计方法

为了削弱大气延迟对干涉结果的影响以提高InSAR的测量能力,本文在InSAR大气相位特征分析的基础上,研究了一种新的InSAR大气相位建模与估计方法.首先采用稳健估计确定大气垂直分层部分的模型参数,然后利用基于Matern模型的Kriging插值估计大气紊流部分,最后应用估计的大气垂直分层和紊流资料改正InSAR测量结果.利用覆盖河南义马地区的ASAR数据对本文提出的方法进行了验证,结果表明去除大气影响后,InSAR重建的DEM与参考DEM的高程差异的均方误差由19.5m降至5.3m,精度提高了约72%.同时,改正后的干涉图更合理地揭示了义马矿区的沉降漏斗情况,进一步验证了本文方法的有效性.     

基于InSAR技术的喀什-乌恰交汇区地壳垂直形变特征分析

利用喀什-乌恰交汇区2004—2010年间的ENVISAT ASAR数据,采用层叠InSAR技术获得了喀什-乌恰交汇区地壳垂直形变速度场,并结合研究区GPS观测数据结果,分析了喀什-乌恰交汇区地壳形变特征。结果显示,喀什-乌恰交汇区地壳垂直形变速率约为?1—2mm/a,其中,乌恰南边的山区形变量最大,形变速率达到2mm/a,是整个研究区中隆升最明显的区域;而喀什、阿图什一带形变量比较小,基本在0—1mm/a。卡兹克阿尔特和阿图什南翼断裂为乌恰以南的隆升区域到喀什、阿图什垂直形变平稳区域的梯度带,这个区域吸收了1—2mm/a的垂直形变能量和7—9mm/a的水平形变能量,是喀什-乌恰交汇区中主要的地壳形变能量消耗地带。     

用InSAR数据得到的鲜水河断裂西北段地震间滑动速率

鲜水河断裂是青藏高原东部边缘附近的高活动性走滑断层系统。我们使用多干涉图方法由ERS-1/2和欧洲环境卫星所获得的十年SAR数据来构建由于鲜水河西北段地震间应变积累而产生的视距形变速率图。该速率图显示了与断层有关的清晰的形变梯度,但是从地表断层迹线看稍向东偏移。通过使用蒙特-卡洛方法对InSAR速率图和GPS数据的共同反演,当锁定深度为3～6km时,以90%置信水平估算出滑动速率为9～12mm/a。此滑动速率与全新世断层滑动速率及历史地震相吻合。我们的结果也揭示不存在显著的跨断层拉伸。将来,上升和下降轨道得出的InSAR数据可能会进一步约束此断层的3D断层滑动速率。     

ESTIMATING PRESENT SLIP RATE OF THE FAULTS IN THE WEIHE GRABEN USING ENVISAT ASAR DATA

Most great(M≥8)earthquakes during modern times have occurred in interplate regions or major continental collision zones, such as Sumatra, the Japanese island arc or the San Andreas fault zone. Continental faults slip at a much lower rate than boundary faults, but they also have the potential of generating large earthquakes. For example, the 2008 Wenchuan earthquake with a magnitude of 7.9, the slip rate of seismic fault is less than 3mm/a. They also have the potential to be significantly deadlier than those on plate boundaries because of the long repeat times and lack of preparedness. The January 23rd 1556 Huaxian earthquake in Shaanxi Province, central China, is the deadliest in history with an estimated death toll of ~830 000 from building collapse, land-sliding, famine, and disease. The earthquake occurred in the graben of the Weihe River.
The Weihe Graben in Shaanxi Province has recorded multiple earthquakes in history, whereas most active faults within the graben have a low slip rate over geological times (~1mm/a). The slip rate of faults is an important parameter for assessing the risk of earthquakes and the interval between major earthquake recurrences. In order to obtain the quantitative information of faults slip rate, traditional geological methods or geodetic observation techniques can be used. Interferometric synthetic aperture radar(InSAR), as a modern geodetic observation technology, has the characteristics of all-weather and day-and-night imaging capability, wide spatial coverage, fine resolution, and high measurement accuracy. InSAR offers the potential to measure interseismic slip rates on faults at a resolution of millimetres per year. In this study, we use InSAR data to analyze the present deformation of the Kouzhen-Guanshan, Weihe and North Qinling faults in the central part of the graben.
We collected 32 European Space Agency(ESA's)Envisat ASAR images from descending track 161 between 2003 and 2010, and processed them using ROI_PAC. The precise orbit determination from the Delft Institute for Earth Oriented Space Research(DEOS)was applied to correct for orbital effects. The topographic contribution was simulated and removed using the 90m resolution Shuttle Radar Topography Mission(SRTM)Digital Elevation Model(DEM)from CGIAR-SCI. Each interferogram was downsampled to 64 looks in the range direction (1 280m). Before phase unwrapping, a weighted power spectrum filter was applied to improve the signal-to-noise ratio. The branch-cut method was used for phase unwrapping. Phase unwrapping errors were checked by summing around a closed loop. All the major unwrapping errors were identified and corrected manually. We obtained a total of 98 interferograms with a spatial baseline of smaller than 300m, and selected 33 interferograms whose coherence is well preserved for time-series analysis. The time-series analysis was implemented using the π-RATE software package. It uses the geocoded interferograms from ROI_PAC to create a minimum spanning tree(MST)network, from which the orbital and topographically-correlated atmospheric errors are estimated. The MST network connects all epochs with the most coherent interferograms,including no closed loops of interferograms. The network approach is able to improve the estimation of orbital error by ~9% compared to the independent interferograms approach. The orbital errors are empirically modelled as planar or quadratic ramps. The topographically-correlated atmospheric correction was applied to each interferogram after having corrected for the orbital errors. Following creating a minimum spanning tree network, correcting for orbital and topographically-correlated atmospheric errors, and calculating the covariance matrix, we obtained the 7-year average slip rate of the faults that we are focused on.
Our results show that the faults across the Weihe graben all have a small slip rate of less than 2mm/a. The Kouzhen-Guanshan Fault does not show any evident deformation signal. The Weihe Fault seems to show 1mm/a normal faulting in the satellite line-of-sight direction. In addition, we find ~10mm/a surface subsidence of the Xi'an City between 2003 and 2010. We use the stable Ordos block as a reference to assess the accuracy of our InSAR time-series analysis. Assuming the Ordos block has no internal deformation, we calculated the error of the InSAR rate map to be (-0.1±1)mm/a, indicating that our result is reliable. This paper presents a preliminary result of the present deformation of the Weihe Graben. InSAR is a powerful technique for monitoring active faults on a timescale of tens of years, and can be used for seismic hazard assessment in the future.     

基于PSInSAR技术的海原断裂带地壳形变初步研究

常规差分干涉测量(DInSAR)受时间、空间失相干的严重制约和和大气延迟等相位误差的影响,难以实现对长期累积微小地壳形变场的有效探测.PSInSAR技术克服了常规DInSAR的局限性,能够高精度监测微小地壳形变.本文首先介绍了PSInSAR技术的算法模型和处理方法.该方法通过二维线性相位模型,对时序干涉图象上相干点目标...     

PS-InSAR技术在西秦岭北缘断裂带地壳微小形变监测中的应用

D-InSAR技术可以测得地壳垂直形变精度达到mm级,但由于其受空间、时间失相干和大气延迟的限制,导致其在监测地壳长期缓慢形变中的应用受到限制。而PS-InSAR作为D-InSAR技术的创新,在克服时间失相干的同时还可以计算并消除大气影响,使得干涉处理得到的结果更加精确。文中以西秦岭北缘断裂带甘谷地区为实验区,利用从2008年5月至2010年9月共14景ENVISAT ASAR数据,采用PS-InSAR技术对该实验区地壳微小形变进行探测。研究结果得到西秦岭北缘断裂带甘谷地区断裂带南北两盘的相对滑动速率约为5mm/a,点目标的形变速率和形变方向均与西秦岭北缘断裂的左旋运动特征相符,并与其他学者的研究结果有较好的一致性,表明PS-InSAR技术在监测地壳微小形变中具有广阔的应用前景和巨大的发展潜力。     

PS-InSAR processing methodologies in the detection of field surface deformation—Study of the Granada basin (Central Betic Cordilleras,southern Spain)

Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms.Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian–African plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates are in the order of ～1 mm/yr, which are at the feasibility limit of current InSAR techniques.In order to evaluate whether, under these conditions, InSAR techniques can still be used to monitor deformations we have applied and compared two PS-InSAR approaches: DePSI, the PS-InSAR package developed at Delft University of Technology (TU Delft) and StaMPS (Stanford Method for Persistent Scatterers) developed at Stanford University. Ground motion processes have been identified for the first time in the study area, the most significant process being a subsidence bowl located at the village of Otura.The idea behind this comparative study is to analyze which of the two PS-InSAR approaches considered might be more appropriate for the study of specific areas/environments and to attempt to evaluate the potentialities and benefits that could be derived for the integration of those methodologies.     

雷达干涉PS网络的基线识别与解算方法

时序雷达干涉图中的永久散射体(PS)可看作“天然GPS点”, 以构成网络用于监测长期的地表形变. 本文提出采用邻接矩阵拓扑模型对基于Delaunay剖分算法生成的PS网络进行基线识别, 并采用时序相干最大化算法求解PS基线的线性形变速度增量和高程误差增量. 该数据模型和计算方法被应用于探测香港地区2006~2007年间的区域地表沉降. 实验研究采用由Envisat卫星ASAR传感器对该地区成像所获取的时序SAR影像作为数据源, 并联合该地区12个GPS连续运行参考站的观测数据予以大气修正和地面控制. 实验结果表明, 该模型和方法应用于地表形变测量是有效的和可靠的, PS网络方法探测地面沉降的精度约为±2.0 mm/a.