Acquisition And Application Of Three-dimensional Deformation Fields Based On InSAR And Multi-source Data

Interferometry Synthetic Aperture Radar (InSAR) has been developed rapidly inthe last few decades, which provides a tool for imaging earth surface deformationcontinuously with a wide coverage at spatial resolutions of a few tens of meters fromspace. However, InSAR measures the change of path of radar waves in line-of-sight(LOS), which is the sum of contributions from horizontal and vertical deformationcomponents. A3-D deformation vector cannot be achieved by InSAR, which is calledLOS ambiguity of InSAR. As for the deformation induced by earthquakes,engineering constructions, and tectonic movement, detailed3-D deformationinformation is required to better understand the style of fault movement, deformingfeatures and seismogenic mechanisms, or improve monitoring and evaluation of otherpotential hazards such as land subsidence, landslides, and volcanoes This thesisfocuses on the issue of LOS ambiguity of InSAR, attempting to resolve it byexpanding two existing methods: inversion from multi-LOS InSAR observations andjoint inversion using GPS and InSAR. Then they are applied separately to3Ddeformation acquisitions for the Wenchuan and Yushu earthquakes and the Haiyuanfault, respectively.The main contents of this thesis are as follow:1. Research of methods(1) The relationship between3-D GPS deformation and1-D LOS InSARdeformation is derived, which indicates the limitation of InSAR technique,so-called LOS ambiguity of InSAR. Two methods to solve this problem, invertingfrom multi-LOS InSAR observations and jointly inverting using GPS and InSAR,is presented, and their theories and algorithms are discussed in detail.(2) Resolving3-dimensional coseismic deformation from multi-LOS InSARobservations：3-D deformation components are resolved from3different InSARobservations from3different incidence angles, which make the components moreaccuracy and avoid some uncertainties from unjustified assumptions. However, it is difficult to meet the requirement of multi-LOS observations.(3) Resolving3-dimensional interseismic deformation from PSInSAR and GPS:Using the3-D interseismic deformation field model, the deformation componentsare resolved by PSInSAR data combined with GPS data. The surface variables ofthe research area are obtained by the PSInSAR method. Combined with GPShorizontal deformation observations, based on interpolation algorithm,3-Dinterseismic deformation field can be obtained.2. Case studies of earthquakesFirst, coseismic deformation of the2008Wenchuan earthquake is acquired byusing InSAR technology and its characteristics are analyzed. The accuracy of thecoseismic deformation by InSAR is then evaluated and corrected coupled withrelevant GPS measurements on the coseismic deformation. Specifically, this workinterpolates the GPS horizontal measurements according to the characteristics of thecoseismic deformation and resolves the vertical coseismic deformation from InSAR toobtain the3-D coseismic deformation of the2008Wenchuan event.Using the multi-band method, this study resolves3-dimensional coseismicdeformation. Coseismic deformation of the2010Yushu earthquake is measured by Lband ALOS PalSAR and C band ENVISAT ASAR interferometry. With the help ofmultiple-band interferometry and MAI technique, this work resolves the3-Dcoseismic deformation of the2010Yushu earthquake, based on which it analyzes theslip motion pattern and surface ruptures of this event.This thesis presents the principle, algorithm and data processing procedures ofPSInSAR. Using21scenes of ENVISAT ASAR data from2003to2009and thePSInSAR technology presented, this work examines the small crustal deformationacross the Haiyuan fault zone. The result shows that most coherent point targetsdisplay a left lateral slip rate about6-7mm/a. This thesis also analyzes the strain ratefeatures of PS targets, which cumulated average displacement of about4.2cm in2003-2009and are roughly in agreement with that from GPS measurements andgeological investigations. In addition this work also resolves the3-dimentionaldeformation using InSAR and GPS measurements, yielding the strain accumulationpattern across the Haiyuan fault. Through method studies and comparisons of earthquake cases, this thesis attainsto the following conclusions:(1) The coseismic deformation fields of the2008Wenchuan and2010Yushuearthquakes are obtained using InSAR technology, indicative of patterns of surfaceruptures by the shocks.The InSAR analysis of the Wenchuan earthquake shows that the coseismicdisplacements are primarily distributed in a500km long and450km wide area. Theinterferograms are centered along the Yingxiu-Beichuan fault with intense fringes.This deformation field extends southward to Lushan and Chongqing and northward toNanping, Wudu and Kangxian. The inteferograms reveal that both sides of InSARcoseismic deformation along the causative fault are asymmetric, which indicates thatthe deformation is unevenly distributed along the fault strike. Also near Yingxiu at thesouthwestern end of the fault, dense fringes are present showing intense coseismicdeformation. Near Beichuan there are fringes t parallel to the fault strike indicatinglarge coseismic displacements. Near Wenchuan the fringes start to wrap around theepicenter, implying the southern end of the surface rupture. Nearby Qingchuan, sameas near Wenchuan, the fringes clearly show the northern end of the ruptures. Overallthe InSAR interferograms display an unevenly distributed coseismic deformation fieldand obvious segmentation features.As revealed by the InSAR deformation, the peak motion of each side along thecausative fault reaches~42cm away from the satellite on the south side and~38cmtowards the satellite on the north side, respectively. The fault rupture strikes NW-SE,with an average trend of310o. Surface ruptures extend for about76km and break thesurface on its eastern segment for about32km. The surface ruptures can be easilyidentified by the discontinuity between both sides through the offset images. Therange offset map and the azimuth offset map show similar patterns of the surfacedisplacement, although the azimuth displacement map gives a more clear trace of thesurface rupture. This work establishes56km length of clear surface ruptures at easternsegments, which is largely in agreement with field investigations.(2) By using jointly InSAR and GPS, the3D deformation field of the2008Wenchuanearthquakes is established, and the causative fault is characterized. The results show that the southern section of the Longmenshan fault has aprominent northward motion with right-slip component. Its thrust componentdecreases from north to south gradually, largely concentrating along the sectionsYingxiu-Lianshanping, and Chaping-Beichuan-Nanba. In the former section, there is amaximum of east-directed displacement which is up to5.85m on the hanging wall ofthe fault. While merely1.00m westward displacement is seen on foot wall. In thelatter section, displacement on the foot wall reaches-2.80m, and eastward2.90m onthe hanging wall. Overall, eastward motion on the hanging wall is dominant in thesouthearn section, while opposite motions on the foot wall are obvious in the middleand north sections of the fault.(3)Using multi-band InSAR data, the3D deformation field of the2010Yushuearthquake is resolved.This analysis is based on ALOS and ENVISAT data and MAI method fordisplacements in azimuth. The map of vertical components shows two subsidencecenters on the southwest side of the fault, of which one is nearby the main surfacerupture with vertical depression up to23cm; and the other lies at the northeastern endof the fault, coinciding with the aftershock Ms6.1on14April2010. Horizontaldisplacements indicate dominant left slip. The analysis Combines with the Yushuearthquake left lateral strike slip focal mechanis. The direction of movement is in thestress concentration area, and medium uplift movement occurs. The end of themovement is in the stress tensile area, so the medium occur settlement movement.The vertical deformation field and the Yushu earthquake motion properties areconsistent.Due to the complexitys of Yushu earthquake movement patterns andvertical deformation, the settlement area appears the near of the faults of focalmechanisms solution. The reliability of the results and the specific reasons still needto analyse combined with other data.(4) By joint usage of PSInSAR and GPS, the3D deformation field of the Haiyuanfault is casted, showing its feature of current crustal motion.The results indicate that the crutal deformation is distributed along NW directionwith maximum EW displacement35mm. The displacements on the south side of thefault are greater than that on the north side, indicative of left slip. The3D deformation field also reveals vertical motion with maximum of6mm and minimum-5.8mm. Thesouth side is rising and north side declining, implying dipping slip coexisting, inagreement with many previous studies.