【作者】 洪顺英；

【导师】 单新建； 申旭辉；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2010， 博士

【摘要】 差分合成孔径雷达干涉测量技术(Differential Interferometry Synthetic Aperture Radar,DInSAR)是地震形变监测的一种重要方法,但是其存在视线向(Line of Sight,LOS)模糊的问题,即DInSAR测量的形变场并不是地表真实的垂直向、东西向、南北向形变场,而是地表形变场在卫星视线向上的投影。为了解决这一问题,在多视线向差分干涉测量技术的基础上,本文首先归纳提出了直接解算模型、结合模拟法解算模型、结合Offsets法解算模型与GPS测量视线向投影模型共4种方案。前三种方案均可进行地震三维形变场解算,为正模型;第四种模型为利用GPS三维同震测量结果反算LOS向形变量,为反模型,可用于检验与评估同震形变干涉测量的精度。然后,分别以改则地震、于田地震、巴姆地震、汶川地震为应用实例,进行4种方案的尝试,评价每种方案的优劣势与适用性。同时,分别获取了改则地震、于田地震、巴姆地震的三维同震形变场,以及汶川同震形变场及精度评估结果;并通过多视线向及三维同震形变场的特征分析,分别获取了改则地震、于田地震、巴姆地震、汶川地震的破裂模式。本论文研究的主要贡献在于取得了如下的结果和认识:[1]提出了4种DInSAR测量视线向模糊的解决方案直接解算模型:直接利用三种不同视线向的同震形变场,构建三维形变解算模型进行解算。其优势是具有较高的可信度,避免了模拟、假设等方法带来的不确定因素。但是,获取三种不同视角的同震形变场比较困难,南北向形变解算精度无法保证。结合模拟法解算模型:利用升、降轨两种视线向的同震形变场,以及模拟的南北向形变场,来构建三维形变解算模型进行解算。其优势是可以用模拟值代替观测值,降低对观测数据的要求;但是,模拟的南北向形变场与真实的南北向形变场存在不可避免的偏差,不同的断层模型可能产生不同的模拟结果。结合Offsets解算模型:利用Offsets法测量获取升、降轨两种模式的方位向同震形变场,以及DInSAR测量获取的升、降轨两种模式的视线向同震形变场,来构建三维形变解算模型进行解算。其优势是利用Offsets测量法获取方位向形变量参与解算,降低了对观测数据的要求。同时,结合Offsets法进行3D形变解算总体上优于纯粹的Offsets法,特别是垂直向、东西向解算精度与效果明显好于Offsets法。纯粹的Offsets法似乎更有利于解算南北向形变;而干涉测量结合Offsets法则更有利于解算垂直向、东西向形变。GPS测量LOS向投影模型:利用GPS实测三维形变量,通过其LOS向投影模型投影至卫星观测视线向,并与DInSAR测量结果对比,以评价同震形变场的精度。其优势在于将GPS与DInSAR两种测量手段对比分析同震形变场特征。主要问题是,GPS与DInSAR测量两种手段存在时空尺度、参考框架的差异与误差影响。[2]结合多视线向DInSAR技术,基于3D解算模型,实现了典型震例3D同震形变场解算针对干涉测量的视线向模糊问题,本文提出的4种有利的解决方案:直接解算模型、结合模拟法解算模型、结合Offsets解算模型与GPS测量LOS向投影模型。利用前三种模型进行3D同震形变场解算,其基本思路是利用多视线向同震形变干涉测量结果,并结合模拟或Offsets测量结果,构建3D同震形变解算方程,进行3D同震形变场解算。通过解算,本文共获取了改则地震、于田地震与巴姆地震3个典型震例的3D同震形变场。[3]基于GPS测量LOS向投影模型,实现了GPS与D-InSAR技术的结合,完成了汶川同震形变场的精度评估与误差校正通过GPS测量LOS向投模型,利用汶川地震26个GPS三维同震形变测量的结果,对汶川同震干涉形变场的精度进行评估。结果显示,GPS与DInSAR测量结果反映的地震形变特征是一致的。L波段干涉测量的大气延迟误差影响具有线性分布的特点,可通过GPS与干涉测量结果之间的线性回归分析,能较好地校正InSAR测量结果,使InSAR与GPS测量之间的平均绝对偏差从15.2cm提高到4.9cm。[4]取得了汶川同震GPS测量与DInSAR测量的差异性认识GPS与DInSAR两种测量方法的偏差主要来源于以下几个方面:1、时间尺度差异性,GPS同震测量的时间一般临近于地震发生时刻,而DInSAR同震测量的时间与地震发生时刻相差较大,汶川地震后最早的一期ALOS卫星数据已经是一周之后;2、测量误差影响,主要指GPS垂直向测量误差与L波段的DInSAR测量大气延迟误差;3、空间尺度的差异性,GPS测量的形变量是GPS站点位置的形变量值,而DInSAR测量的形变量是某个图像像元的平均形变量,两者在空间尺度上存在差异性;4、参考体系的差异生,GPS同震测量一般相对于欧亚参考框架,DInSAR测量的参考点为雷达图像中选定的解缠参考点。正是由于这些影响,使得GPS测量与DInSAR测量的结果在一定程度上存在不可避免的偏差,造成汶川GPS同震形变测量LOS向投影值总体上小于干涉同震形变观测值。[5]取得了汶川地震同震形变场特征与逆冲型破裂的认识汶川地震同震干涉形变场特征分析表明,汶川地震以NE向地震断裂带为分界线,西北盘青藏高原巴颜喀拉块体(上盘)总体上表现为的视线向沉降形变趋势,东南盘四川盆地(下盘)总体上表现为视线向隆升形变趋势。西北盘青川高原巴颜喀拉块体与东南盘四川盆地两者在此次地震中表现为强烈的对冲运动模式,并且主要表现为逆冲型,并伴随右旋走滑。巴颜喀拉块体沿地震破裂带呈逆冲抬升的同时,在巨大的向东推力作用下,上覆于四川盆地朝东挤出。正是由于西北盘向东的运动趋势及右旋走滑,造成其发生远离升轨ALOS卫星的运动,并且这种LOS向远离运动量大于其垂直向逆冲隆升造成的LOS向缩短量,才使西北盘大部分区域表现为LOS向沉降形变特征。四川盆地对巴颜喀拉块体起到了阻挡作用,在发生沉降形变的同时,下覆于巴颜喀拉块体朝西俯冲。也正是由于东南盘向西俯冲的运动趋势及右旋走滑,造成其发生靠近升轨ALOS卫星的运动,并且这种LOS向靠近运动量大于其垂直向俯冲造成的LOS向缩短量,才使东南盘大部分区域表现为LOS向隆升形变特征。[6]基于3D同震形变场特征分析,获取了典型震例的地震破裂模式①改则3D同震形变场特征与双震破裂模式改则3D同震形变场特征分析表明,Mw6.4级主震的发震断层(东发震断层、走向NNE、倾向NW)西北盘(上盘)主要表现为沉降形变、朝南形变以及朝东形变特征;Mw5.9级余震的发震断层(西发震断层、走向NNE、倾向NW)西北盘(上盘)主要表现为沉降形变、朝北形变以及朝西形变特征。根据3D同震形变场特征分析与三维显示,获取了改则双震破裂模式:左旋走滑的改则-洞错断裂与依布茶卡-日干配错断裂的分阶部位(左阶)的张性应力积累,使得沿NNE向发育的正断层先后发生两次张性为主的破裂;Mw6.4主震表现为正断左旋为主,并伴随略微向东旋转破裂机制;Mw5.9级余震表现为正断破裂为主,伴随略微右旋走滑破裂机制。②于田3D同震形变场特征与三分段正断左旋破裂模式于田地震发震断层由北至南可依次分为三段,分别为北段No.1、中段No.2与南段No.3。3D同震形变场结果显示:三分断断层断层西盆(上盆)整体上呈沉降形变特征,断层东盆(下盆)整体上呈隆升形变特征;断层No.1与断层No.3的西盆呈朝西运动形变,而断层No.2的西盆,特别是靠近断层附近,具有朝东运动形变趋势;断层No.1与断层No.2的西盆呈朝南运动形变,东盆呈朝北运动形变,而断层No.3西盆大部分呈朝南运动形变,东盆呈朝南运动形变。根据3D同震形变场、形变模拟与三维显示综合分析,获取了于田地震的破裂模式:三分段断层均呈左旋正断破裂模式,空间分布上具有左阶雁列式分布的特征。③巴姆3D同震形变场特征与右旋走滑为主、兼具东西向水平左旋旋转破裂模式巴姆地震发震断层为近南北向,同震形变场具有四象限特征。3D同震形变场分析表明:西北翼具有隆升、向北与向西运动特点;东北翼具有沉降、向南与向西运动特点;东南翼具有隆升、向南与向东运动特点;西南翼基本缺失。根据3D同震形变场特征与三维显示,获取了巴姆地震的破裂模式:巴姆地震主要受到西北方向与东南方向的主拉应力而产生破裂,主要以右旋走滑为主,兼具东西向水平左旋旋转机制。[7]通过对比优劣势,初步分析了四种模型的适应性针对垂直向与东西向形变解算,直接解算模型最是最有利的,其次是结合模拟法解算模型,再者是结合Offsets法解算模型;而针对南北向形变解算,结合Offsets法解算模型是最有利的,其次是结合模拟法解算模型,再者是直接解算模型。根据模型的优劣势,以及其理论与算法特点,按地震破裂断层的走向及破裂机制,本文初步总结出四种模型的适用性情况。四种模型的优劣势与适用性分析结果将为今后的3D形变解算与干涉形变场精度检验提供有益参考。更多还原

【Abstract】 The Dfferential Interferometry Synthetic Aperture Radar (DInSAR) technology is one very important method to monitor earthquake deformation. One of its limitations is that an interferogram only measurementss one component of the surface deformation—in the satellite’s line of sight (LOS), but not the real surface deformation in the vertical and horizontal directions, and this question is named“LOS Amphibious”. In order to overcome this question, based on the Multi-LOS DInSAR technology, this thesis firstly suggests 4 solutions: the model of direct solution, the model of combining the simulation method, the model of combining the offsets method, and the model of projecting GPS measurement to LOS direction. The former three solutions can be used to calculate the three-dimensional (3D) deformation field, which belong to the forward-model. The fourth solution uses the GPS measurements to calculate their LOS deformation, and can be used to inspect and evaluate the accuracy of the coseismic interference deformation field, which belongs to the backward-model. Then, this thesis chooses the Gaize earthquake, Yutian earthquake, Bam earthquake and Wenchuan earthquake to evaluate the advantages and disadvantages of the four models. Finally, this work obtains the 3D coseismic deformation fields of Gaize earthquake, Yutian earthquake and Bam earthquake, respectively, and the coseismic deformation field and precision evaluation of the Wenchuan earthquake. By the characteristic analysis of the Multi-LOS and 3D coseismic deformation fields, this work gives the rupture modes of the four earthquakes, respectively.[1]Four solutions to the problem of DInSAR LOS AmphibiousThe model of direct solution: It uses the coseismic deformation fields of three different LOS directions to set up the solution model of 3D deformation for calculating the 3D coseismic deformation field. It has higher reliability, and avoids the uncertainty of simulation or assumption methods. But, it is usually very difficult to obtain the coseismic deformation field in different LOS directions, and the solution precision of the north-south direction is uncertain.The model of combining the simulation method: Using coseismic deformation fields of ascending-orbit and descending-orbit modes in two different LOS directions, and the simulated NS direction coseismic deformation field, it constructs the 3D deformation solution model for calculating the 3D coseismic deformation field. Its advantage is to use the simulation value to replace the measured value, which reduces the requirement of observation data. But the simulated deformation fields are inevitably different to the actual, and the different fault modes can produce various simulative results.The model of combining the offsets method: Using coseismic deformation field of ascending orbit and descending orbit modes in two different azimuth directions by offsets measurements, and the coseismic deformation field of ascending orbit and descending orbit modes in two different LOS directions by DInSAR, it sets up the 3D deformation solution model for calculating the 3D coseismic deformation field. Its advantage is to use the azimuth coseismic deformation field to resolve the 3D deformation, which reduces the requirement of observation data also. Furthermore, the calculation precision of this method is better than the pure offsets way, especially in vertical and east-west directions. The pure offsets method seems more appropriate to calculate the north-south direction deformation field, and the combining offsets method is more advantageous to calculate direction deformation fields in vertical and east-west direction.The model of projecting GPS measurements to LOS direction: It projects the GPS measurements of 3D coseismic deformation value to InSAR LOS direction by projection mode, and compares the projection result with DInSAR measurements in order to validate and evaluate the accuracy of the coseismic interference deformation field. Its advantage is to combine the GPS with DInSAR measurements to analyze the characteristics of coseismic deformation. But there are some deviations between the GPS and DInSAR measurements because of the different spatio-temporal scales of the two methods.[2]The 3D coseismic deformation fields of typical strong earthquakes calculated based on the 3D resolving modes, combined with Multi-LOS DInSAR technologyIn order to overcome the“LOS Amphibious”of interferometry, this thesis proposes the four resolving methods: the model of direct solution, the model of the combining simulation method, the model of combining the offsets method, and the model of projecting GPS measurements to LOS direction. And the 3D coseismic deformation fields are calculated based on the former three solutions, which construct the 3D resolving equation using the Multi-LOS interferometry, simulated and offsets results. And then, three 3D coseismic deformation fields of typical strong earthquakes are obtained, i.e. Gaize earthquake, Yutian earthquake and Bam earthquake.[3]Combining the GPS with DInSAR to evaluate and revise the coseismic deformation field of Wenchuan earthquake, based on the model of projecting GPS measurements to LOS direction.This work uses the 3D coseismic deformation measurements of twenty-six GPS stations to evaluate the precision of Wenchuan coseismic deformation field, based on the model of projecting GPS measurements to LOS direction. The evaluation result shows that the seismic deformation characteristics shown by the GPS and D-InSAR are coincident. Because of linear characteristics of the atmospheric delay error of L-band interferometry, the DInSAR result is corrected by the linear regression analysis of the GPS and DInSAR result, and the average absolute deviation between the GPS and DInSAR measurements is reduced from 15.2 cm to 4.9 cm.[4]On the deviation between GPS and DInSAR measurements of Wenchuan earthquakeThe deviation between the GPS and DInSAR measurements probably comes from several aspects: 1.The first is the difference of time scales, as the coseismic GPS measurementss were close to the shock time, but the coseismic interference measurements were much different from the shock time, and the earliest ALOS satellite data of aftershocks was a week later than the shock time; 2.The second is the error influence of measurements, which refers to the vertical deformation error of GPS measurements and the atmosphere delay error of L-band DInSAR measurements; 3.The third is the difference of spatial scales. The deformation value of GPS measurements were observed at the GPS cites, but the deformation values of interference measurements were derived from the pixels of SAR images; 4.The last is the difference of reference systems. GPS measurements usually are referred to the Eurasia system, but the DInSAR measurements are referred to the unwrapped points. Just because of these influences, the results of GPS and DInSAR measurements which have caused the LOS projection of GPS measurements to be smaller than the DInSAR measurements of Wenchuan coseismic deformation.[5]Insights of coseismic deformation field and thrusting rupture of the Wenchuan earthquakeThe characteristic analysis of the Wenchuan coseismic deformation field shows that the coseismic deformation field can be divided into northwest part (hanging wall)and southeast part (foot wall) by the NE-striking seismic rupture; and the northwest part, Bayankala block of Tibet is subsiding mostly in the LOS direction; whereas the southeast part, Sichuan basin is uplifting mostly in the LOS direction.The northwest part Bayankala block and southeast part Sichuan basin collided each other strongly during the Wenchuan quake, and mainly ruptured by thrusting with right-lateral striking component. When the Bayankala block thrust upwards along the sesmic ruptures, it also moved to the east to overlay the Sichuan basin, under the huge push power eastward. And because of the far distance of LOS direction caused by its eastward movement and right-lateral striking larger than the shortening distance caused by its uplifting movement, the Bayankala block shows subsiding characteristic in the LOS direction. When the Sichuan basin thrust downwards along the seismic ruptures to obstruct eastward movement of the Bayankala block, it also moved to west below the Bayankala block. And because of the shortening distance of LOS direction caused by its westward movement and right-lateral striking larger than the far distance caused by its subsiding movement, the Sichuan basin shows uplifting characteristic in the LOS direction.[6]The seismic rupture modes of typical strong earthquakes derived from the characteristic analysis of 3D coseismic deformation fields①3D coseismic deformation field characteristics and double-quake rupture mode of the Gaize earthquake.The characteristic analysis of the 3D coseismic deformation field of the Gaize event shows that the northwest wall of the eastern fault(NNE striking and NW dipping) caused by the Mw6.4 mainshock moved downward and toward to south, and east; The northwest wall of western fault (NNE striking and NW dipping) caused by the Mw5.9 aftershock moved toward to depth, north, and west. According to the characteristic analysis and 3D display, the rupture process of the Gaize earthquake is: tensile stress accumulation in the step position(left step) of left-lateral striking fault of the Gaize-Dongcuo fault and Yibucaka-Riganpeicuo fault maybe had caused the twice normal ruptures along NNE direction. The Mw6.4 mainshock was mainly ruptured by normal and left-lateral striking, with a little rotation to east; and the Mw5.9 aftershock was mainly ruptured by normal faulting, with a little right-lateral striking.②Yutian 3D coseismic deformation field characteristic and rupture mode of three-segments normal faulting with left-lateral striking.The seismogenic fault of Yutian earthquake can be divided into three-segments, which are north section of No.1, middle section of No.2 and south section of No.3, respectively. The 3D coseismic deformation field shows that the western wall (hanging wall) of the three-segment fault moved down overall, whereas the eastern wall uplifted; the western wall of the No.1 and No.3 faults moved toward to west, whereas the western wall especially nearby to the No.2 fault moved toward to east, and all the eastern wall of the three-segments moved toward to east (dE); the western wall of the No.1 and No.2 faults moved toward to south, whereas their eastern wall moved toward to north, and both the western and eastern wall of No.3 fault moved toward to south(dN). By the comprehensive analysis of the 3D coseismic deformation field, simulated deformation field and 3D display, the seismic rupture mode of Yutian earthquake is: the three-segment faults of the Yutian earthquake are mainly ruptured by normal faulting and left-lateral striking, and spatial distribution of the three-segment faults is featured by left step en echelon.③3D coseismic deformation field characteristic and rupture mode of dominant right-lateral striking, with a little left-lateral horizontal rotation in the east-west direction of the Bam event.The seismogent fault of the Bam earthquake is nearly north-south striking, and the coseismic deformation field can be divided into four quadrants. The characteristic analysis of the 3D coseismic deformation field shows that the northwest quadrant uplifted and moved to north and west; the northeast quadrant moved down, to south and west; the southeast quadrant moved toward to up, and to south and east; the southwest quadrant was losed during 3D solution. According to the characteristics analysis and 3D display, the rupture mode of Bam earthquake is: under the principal tensile stress of northwest and southeast direction, the Bam earthquake was ruptured mainly by right-lateral striking mechanism, with a little left-lateral horizontal rotation in the east-west direction.[7]?Primary applicability of the four models determined through comparing and analyzing of the advantages and disadvantages,。By computing the deformation in the vertical direction (dU) and east-west direction (dE), the mode of direct solution is preferred, the model of combining the simulation method is the next choice, and the model of combining the offsets method is the last choice; whereas, for computing the deformation in the north-south direction (dN), the model of combining the simulation method is best of all, the next is the model of combining the offsets method, and the last is the model of direct solution. Based on the advantages, disadvantages and characteristics of the models and arithmetic, this articles sums up the primary applicability of the four models according to the strikes and rupture mechanisms of seismic faults. The analysis result of advantages, disadvantages and applicability is beneficial to resolving the 3D deformation field and evaluating the precision of interference deformation field in the future.更多还原