| In this thesis, I have researched the deformation monitoring of ChangbaiShan Tianchi volcano based on "two-pass" Differential SAR Interferometry (D-InSAR).I have processed 15 JERS-1 SAR data which were obtained In the period of 1992 to 1998 with the D-InSAR technology when I have analyzed many kinds of constraints for InSAR, especially the error sources for "two-pass" D-InSAR.I have created a model to select the reference image by the integrated coherence coefficient. When the model equation has been solved, I have selected a image whose coordinate system will be used for the reference coordinate system. Then all the SLC are registered to the reference coordinate system.The data whose baseline is looger than the critical baseline is low coherence, so they have been excluded from the data which will be processed. Additionally, the data which are extremely affected by the bad DEM were excluded. Finally, 35 image pairs were chosen which the good combination for the processing. By analysis of the deformation field rigorously and in combination with the previous studies, the the main results and innovation are obtained as follows.Investigating geography and geological conditions of the ChangbaiShan Tianchi volcano area.With the development of local tourism in recent years, the traffic conditions have been impoved a lot around the ChanbaiShan Tianchi volcano area. Now it is much more convenient for scientific researchers to carry out field work in this area, and to lay GPS mobile stations and leveling routes for vocano observations.The elevation of the ChanbaiShan reaches a climax at the main peak, and then gradually decreases around. This area is characterized by luxuriant vegetation, poor weather condition, hard terrain, high altitude, long-period and deep snow. Over the tens of kilometers distance between the peak and foot of the mountain, the distribution of animaland plant alternation is in obvious regularity. Four types of natural landscapes, changing from the temperate zone to the frigid zone, are distributed vertically in the ChangbaiShan mountain, forming a distinctive natural character. The ChanbaiShan Tianchi volcano is a large and complex volcano. It lies at the front of west Pacific plate subduction, located at the north margin of Sino-Korean craton, belonging to the edge of the transition zone from the inner continent to the active continent margin. The basement is composed by ancient metamorphic series of middle Archean and late Proterozoic era, and lots of granite of Mesozoic era; with scattered Paleozoic sedimentary cover exposed. A series of Mesozoic continent sedimentary basins developed, with relatively strong intermediate-acidic magma activity. There are many volcano activities in the ChangbaiShan Tianci since Cenozoic era, which could be directly compared with tectonic activity in the Japan sea area in the same period. In the ChangbaiShan mountain and its neighbouring areas, several large fault belts in NE, NW and NNE direction form the main tectonic framework since Cenozoic era. Additionally, there are some NWW, NW and nearly EW trending faults which cut through the ChangbaiShan Tianci volcano and it neighbouring faults.Investigating and analyzing methods for volcano deformation monitoring and research background on the ChangbaiShan Tianci volcano deformation measurement.Measurement of surface deformation is the main way to monitor magamation and to predict volcanot eruptions. Most volcanos have obvious surface deformation before their eruptions. Precise deformation measurements have significant contribution to volcano activity research and eruption prediction.This thesis introduces several methods for volcano deformation monitoring and the techniques applied to th ChangbaiShan Tianci volcano area. After thorough discussion on InSAR advantages for volcano area deformation measurement, this thesis focuses on using InSAR to obtain deformation between 1992-1998 in the ChangbaiShan Tianci volcano area, and makes detailed analysis on the InSAR result. Finally, this thesis concludes that InSAR is not only a good alternative for conventional deformation measurement techniques, but also capable of acquiring mssing deformation in conventional measurements by taking use of historic SAR data.Analyzing limitations of InSAR application and D-InSAR’s errors Decorrelation and atmosperic effects are the inevitable limitaions in repeated orbit interferometry. Until now, there is still no perfect method to remove the atmosperic effect on InSAR application. In addition, phase error, orbital error (only applicable for two-pass D-InSAR) and external DEM error will propagate into the final InSAR product to some degree.This thesis systematically analyzes limitations of InSAR application, especially the error sources of two-pass D-InSAR technique, which inculde time baseline, doppler centroid frequency difference, spatial baseline, thermal noise, body scatter and data processing. This thesis discusses each error in two-pass D-InSAR technique, and analyzes their influences quantitatively by formulas.Selecting reference coordinates to coregister all SLC imagesThis work constructs a model to choose a reference image for SLC coregistration. After general consideration on time baseline, spatial baseline, Doppler centroid frequency difference and season discrepancy for image acquisition, the image 19950816 (named by imaging date) was picked as the master image to determine reference coordinates. All SLC are coregisterred to the coordiantes of the reference image. This operation could simplify coregistration between each image pairs in the next step, and most importantly, it could ensure all interferograms are in the same SAR coordiantes, so that phase stacking process of images could be facilitated.The D-InSAR deformation fields of ChangbaiShan Tianchi volcano is obtained.Finally, this work abtained 11 fine D-InSAR deformation fields in this area. I have analyzed the deformation in the regions which were less affected by DEM errors or atmospheric effects. The results shows that the volcano is bulging at the largest rate 5mm/a during the period of 1994 to 1998. The above result was compared with the leveling data which were obtained during the period 2002 to 2005. In combination with the earthquake catalog during 1990 and 2010,the result indicates that the ChangbaiShan Tianchi volcano is not very active in this period.Atmospheric effection correction by the phase stacking methodI have corrected the atmospheric effection using the phase stacking method for 6 differential interferograms. The method has successfully reduced the impact of atmospheric effects. The correction results can not reflect accurately the deformation characteristics of the study area for the data which were stacked are obviously affected by DEM errors. Nevertheless the annual rate of deformation obtained after the atmospheric effection correction still indicates that the deformation of the ChangbaiShan Tianchi volcano in the period 1992 to 1998 is weak. This result and the earthquake catalog in the period 1990 to 2010 all prove the deformation derived by the D-InSAR analysis presented in this thesis is reliable. |
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