Numerical Modeling Of Surface Co-seismic Deformation And Hypocentral Characteristic Parameters Based On D-InSAR Technology

In this thesis, by means of modern space geodetic techniques in particular D-InSAR(Differential Interferometry Synthetic Aperture Radar) combined with GIS (Geomatic InformationSystem), the geophysical elastic half-space dislocation theory and the computer numericalmodeling method, a study example on strong earthquakes is presented. Using the D-InSAR, aninternational advanced space geodetic technique, combined with GIS synthesis analysis techniqueand MATLAB development kit, a series of seismological geometry and kinematical boundaryconditions are extracted and the D-InSAR interferometry deformation field associated with theKUNLUN Ms8.1 earthquake is achieved. According to the Okada elastic half-space dislocationtheory and the multi-fault segment model, using the forward modeling method, the earthquakedeformation field in the direction parallel to the radar LOS (Line Of Sight) is simulated. Moreover, considering characteristics of the earthquake nonlinear elastic dislocation, the arithmetic ofthe dislocation is improved and an exploratory simulating method of the characteristics is doneand some further cognitions to the earthquake segmentation of surface ruptures and epicentercharacteristics are acquired. Based on them, applying the geophysical boundary element method(BEM), the co-seismic deformation distribution characteristics of the shock region ranging fromthe surface to the depth 20km is simulated. By analyzing these results of D-InSAR, the elastichalf-space dislocation theory and numerical modeling, many of acquaintances distinct fromprevious research results are got, and a suite of the most comprehensive available epicenterparameters (including geometrical and kinematical ones) of the earthquake are presented. Throughthis work, the following conclusions have been obtained:①Using D-InSAR technology, the co-seismic deformation in the near field of the KUNLUNMs8.1 earthquake is obtained.With 20 pairs data of SAR images and external DEM, it takes a period of six months toprocess and obtain 200 G bytes productions including deformation field interferograms, coherenceimages and magnitude images. The D-InSAR LOS interferogram shows that a magnificentearthquake surface rupture zone of length 430 km was produced by the KUNLUN Ms8.1earthquake. The destruction was extremely great in scale that was seldom found in the world. Thespatial distribution of the rupture zone can be divided into two discontinuious segments: theBucadaban Peak-Kunlun mountain was the eastern segment with a length of 350km, strike ofN92-105°E, nearly vertical fault plane and width of the interferometry thermal noise area (viz. theserious surface deformation zone) ranging form several hundred meters to several thousand metersin width. The segment was the main rupture zone of the earthquake which was a simple geologicalstructure with the D-InSAR LOS maximum left-lateral dislocation of 7.4 m. The surface rupturezone was overprinted on the paleo-earthquake relics. It belongs to re-rupture along an existingactive fault. Seeing from the D-InSAR interferogram the Taiyang Lake-Kushuihuan Lake was anewly found rupture segment with a length of roughly 30km, a strike of N92°E, a LOS maximumdeformation 3.0 m, belonging to a new earthquake rupture. Between the east and west segments,there was a 50km long stepover in left-step on which the surface rupture was not found. The D-InSAR interfergram confirms the Kusaihu lake east-Yuxi Peak segment (93.08oE-93.64oE)was the macro-epicenter of the earthquake with maximum LOS dislocation 7.4m(93.60oE).Also the D-InSAR interferogram shows that the two sides of the main rupture have the left-lateralmovement characteristic with strike slip mainly. Because of enhancing and undulation for manytimes, dislocation distribution exhibits a distinct segmentation behavior.②Along the main rupture zone, the D-InSAR LOS change was decomposed.It has been a difficult problem to decompose the D-InSAR LOS change of the surface inInSAR. Using GPS pointed field investigation data, making use of linear interpolation functionfitting rupture feature, referring to observation data, the LOS deformation is decomposed intohorizontal and vertical dislocations for the first time. Along the main rupture zone it representsprecisely three components of strike, dip and tense for elastic dislocation analysis and geophysicalnumerical modeling. Compared the results with real measurements, the horizontal dislocationerror is ±0.27m and the vertical dislocation error is ±0.05m. It shows that the decomposedresults, in particular the vertical value fits better with the observation.③A suite of elastic dislocation and numerical modeling constraint conditions have been obtained,and forward modeling try-and-error scheme has been optimized.Making use of GIS synthetic analysis to geodetic leveling survey data, GPS data, fieldgeological investigation, multi-resolution remote sensing images(TM,ETM,SPOT,IKONOS),SRTM DEM, 1:25,000 digital map and 1:400,000 activity tectonic map etc., by means of theMATLAB numerical calculate program kit, a series of information are extracted, and a fivesegment model is optimized. Appling the analysis method presented by this thesis, seven in tenparameters of calculating Okada elastic half-space dislocation analysis such as geographicalcoordinates(E,N) of the end for each fault segment, the length of segments, strike and thethree components of average dislocation are obtained. The try-and-error method adjusts only threeparameters including the depth of hypocenter, the width of the rupture zone and the dip angle ofthe fault plane. So the method creates a better calculation condition for the forward modeling.④By analyzing the displacement of multi-profile of D-InSAR interferogram, the nonlinear elasticcharacteristics of the co-seismic dislocation is found.Laboratory experiments and in situ measurements in boreholes have shown that many crustalrocks exhibit a nonlinear elastic behavior in compression and tension with a dependence of theYoung's modulus on the minimum principle stress (Peltzer, 1999). The effects of nonlinear elasticproperties of crustal rocks have never been observed in geodetic data because of the low samplingdensity of techniques that make use of ground–based instrument arrays. The radar interferometricmap reveals asymmetric displacement on the two sides of the surface rupture, a pattern that cannotbe explained with the linear elastic theory. By analyzing the co-seismic strain map drawn with D-InSAR and field investigation data, it is found that the two side of the main rupture zone sufferrespectively tensional and compressional action. It was found that the surface deformationpresents dislocation distribution of local linear elastic characteristic and the whole nonlinearfeature that was a new discovery in this work using D-InSAR technique.⑤The general model of the Okada elastic half-space dislocation theory was improved. A linearmodel with multiple-hypocentral, heterogenous dislocation, and multi-rupture segmentsuperposition is preposed.Aiming at the nonlinear elastics characteristics of the Kunlun earthquake, the general modelof Okada elastic half-space dislocation theory is improved. Using the linear model of multi-sources, no n-homogeneous dislocation, and multi-rupture segment superposition, a 34 segmentmodel is designed and the nonlinear elastic characteristics are simulated approximately.Comparing the simulation interfrogram with InSAR's one, whether distribution and trend of thedeformation field, the abundant degree of source parameters and relevant rupture details presented,or the fitting degree to the real investigation result, the 34 segment model has the precisionadvantage over the initial five segment model. Having a better effect upon simulating asymmetry,great dislocation, macro rupture field, non-homogeneity of dislocation than the traditional model,the multi-segment method is a progress of this work.⑥ The BEM(Boundary Element Method)is introduced into geophysics in this thesis. Thenumerical modeling recurs 3D kinematics vision of the earthquake displacement field under thesurface.Based on the range change acquired by D-InSAR interferogram and geometry parametersacquired by the Okada dislocation theory in a closed analytic form, a new 8 segment model isconstructed. Applying the geophysical boundary element method (BEM), 3D distributioncharacteristic of the co-seismic deformation over the shock surface 80,000 km2 and itsunderground 20km depth range is simulated. The 3D displacement field shows that the maximumstrike displacement Ux occurs 15km below the surface of on the two sides of the Kusaiho lakeeast-Yuxi peak segment with maximum dislocation 6.424m, and that maximum dip displacementUy is located 10km below the surface of on the two sides of the Kusaiho lake east-Yuxi peaksegment with maximum dislocation 2.067m, and that maximum dip displacement Uz is located10km below the surface of on the two sides of the Kusaiho lake east-Yuxi peak segment withmaximum dislocation 3.701m. The simulation displacement vectors show that being bounded bythe almost vertical main rupture plane the south wall under thrusts northward with subsidence andthe north wall moves up, and that horizontal offset dominates over vertical displacement so theearthquake was a strike-slip dominant type, and that the south wall moves from west to east whilethe north wall does from east to west so the earthquake was of a left-lateral dominant type. Inconclusion, the KUNLUN Ms8.1 earthquake was produced by a set of steep dip, left-lateral andstrike-slip reverse faults.