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The variation of the azimuth to Doppler center frequency of the terrain observation by progressive scans (TOPS) mode leads to the relative distortion of the phase of the interferogram. Therefore, high registration accuracy is required for interference processing. The Canadian Synthetic Aperture Radar Remote Sensing Satellite (RADARSAT‐2) TOPS mode image is less useful due to poor orbital accuracy and geometric registration accuracy, which makes the interference registration more complicated than it in sentinel SAR remote sensing (Sentinel‐1) satellite TOPS mode. In order to perform the interference processing of the TOPS mode data, this paper uses the cross‐correlation registration to correct the geometric registration results, and then uses the spectral diversity for the second geometric registration correction, and finally uses the enhanced spectral diversity to implement the final azimuth offset correction. Typically, the Doppler centroid estimation from satellite ephemeris parameters and focusing imaging parameters alone does not provide sufficient accuracy. Therefore, a phase increment method is proposed to optimize the Doppler center estimation and the estimated Doppler center is verified by the image bearing power spectrum in this paper. [ABSTRACT FROM AUTHOR]

Objectives: The Sichuan Tibet Railway crosses the Jinsha River specifically the section from Xiongsong Town to Shadong Town, Gongjue County, Tibet Autonomous Region, in which exist strong topography variations and many potential geohazards, and hence it urgent to detect the potential geohazards in this region to ensure the railway safety. Methods: In this paper, 61 Sentinel -1 ascending, 53 Sentinel -1 descending and 7 advanced land observing satellite 2 (ALOS 2) ascending images are used to derive the annual mean deformation rates in the satellite radar line of sight (LOS) with two advanced InSAR (interferometric synthetic aperture radar) approaches, namely generic atmospheric correction online service for InSAR (GACOS) assisted InSAR Stacking and LiCSBAS. The three LOS annual mean deformation rate maps are then used to determine 2D surface movements (one along the slope and the other perpendicular to the slope) in the study region. Results: The comparison between GACOS assisted InSAR Stacking and LiCSBAS results show that they agree with each other with correlation coefficients over 0.92 for the LOS deformation rates and over 0.85 for the 2D deformation rates, suggesting the reliability of GACOS assisted InSAR Stacking. The maximum annual deformation rate of 163 mm/a can be observed in the slope direction and seven landslides (A, B, C, D, E, F, G) can be clearly identified, which in turn lays the foundation for future real-time monitoring. Based on the detailed analysis of the seven regions by using InSAR and optical interpretation results, it is found that the seven landslides had relatively obvious deformation. Landslides A, B, C and D are active landslides, which might cause the result of river blocking due to overall instability. At present, landslides E, F and G are still in the stage of slow deformation. Conclusions: This study also find that GACOS assisted InSAR Stacking can effectively remove long band and topographic related atmospheric delay error with the help of GACOS, which has the advantages of being simple, effective, fast, and easy to popularize and apply. GACOS assisted InSAR Stacking technology can be used to quickly identify potential landslide hazards. [ABSTRACT FROM AUTHOR]

Glacier motion represents a significant reference for the hazard assessment of glacier and glacial lakes.GF-3,as the first civil spaceborne synthetic aperture radar satellite in China,has important advantages in monitoring glacier motion due to its characteristics of all-weather, all-time capabilities and high spatial resolution. Based on five GF-3 images with FS Ⅱ imaging modes, the surface velocities of the Yiga Glacier, located in Nyenchen Tonglha Mountains, are estimated over five time periods using offset tracking technique during November 2017 to March 2018. The results were compared with the offset tracking results of Sentinel-1 images which have a similar time with GF-3 image and based on the assumption that the velocity of the bedrock in the study area should be 0, the velocity residuals of the bedrock in each period are calculated, then the applicability of GF-3 image in monitoring glacier surface motion was evaluated. The results of GF-3 data show that the distribution of the Yiga Glacier motion is similar in four periods, and the maximum surface velocities are all distributed in the central part of the glacier where the elevation changes dramatically. Meanwhile, the results are consistent with the results of Sentinel-1 based on two images. The RMSEs of velocity residuals in the bedrock area in four periods are 1.4 cm/d, 2.0 cm/d, 1.7 cm/d and 2.3 cm/d, respectively, which validate the reliability of the deformation estimated used GF-3 images in this paper. Based on the above analysis, GF-3 SAR data can be used as one of the conventional data sources for monitoring glacier surface movement. Because of its high spatial resolution and high cost performance, GF-3 can play a unique role in monitoring the motions of glaciers in China. [ABSTRACT FROM AUTHOR]

On November 12, 2017, a strong Mw7.3 earthquake occurred in the Sarpol-e Zahab region on the Iranian-Iraqi border, killing more than 500 people. Earthquakes cause serious damage, but do not cause rupture of seismogenic faults on the earth's surface. In order to study the focal mechanism of earthquakes and the crustal deformation caused by earthquakes, this paper uses ALOS-2 and Sentinel-1 satellite data, obtains the seismic co-seismic deformation field by over-differential interferometry, and then uses the reso- lution constrained quadtree sampling method to observe it. The data are sampled for down sampling. On this basis, a two-step inversion algorithm is used to subdivide the fault plane, and the precise geometric pa- rameters and the optimal fault slip distribution are obtained by inversion. The inversion results show that the seismogenic fault is a fault with thrust and dextral strike slip, and the fault strike is determined 347° . The inclination angle is 15°. The distribution of seismic slip is mainly distributed in16 - 19 km. The depth range and the maximum tilting slip are 4.5 m. Based on the inversion of the fault model, the 3D seismic de- formation field is obtained. The results of the 3D seismic deformation field show that the deformation caused by the earthquake is mainly in the vertical direction, and the vertical uplift deformation reaches 78.8 cm. The inversion results of the focal mechanism and the three-dimensional deformation field results are in good agreement with the seismological research results. [ABSTRACT FROM AUTHOR]

The pre-failure evolution of landslides is of great value for the analysis of landslide triggering factors and post-disaster stability assessment. At present, optical images are commonly employed to ana⁃ lyze the pre-failure evolution, but it is well-known that their data availability could be highly limited due to the presence of clouds. With the advance in radar remote sensing and interferometric synthetic aperture radar(InSAR), it could provide a new technical approach for landslide pre-failure detection. In this paper, the 2018 Nanyu landslide in Gansu Province is utilized to demonstrate the capability of InSAR to trace its pre-failure surface displacements using European Space Agency’s Sentinel-1 radar data with a temporal interval of 12 days in different tracks. The results show that the landslide began to deform in June of 2017, and the maximum cumulative deformation reached up to 77 mm in the 13 months before the occurrence of the landslide. The time series InSAR derive displacements and the rainfall data is consistent, suggesting that the rainfall should be one of the triggering factors for the landslide. The study demonstrates the potential of radar interferometry for landslide detection, which can provide insights on landslide triggering factors, landslide disaster prevention and mitigation, and even landslide monitoring and early warning work in the future. [ABSTRACT FROM AUTHOR]

Affected by global climate change，most glaciers in southeastern Tibet have deteriorated more and more frequently. The risk of mountain disasters» such as floods, surges and debris flows， has increased sharply in recent years. This paper implements a research on glacial lakes classification by using multi-source synthetic aperture radar (SAR) images. According to the statistical analysis of intensity difference between signals coming from water and non-water objects，a method of glacial lake extraction and dynamic monitoring based on the intensity standardization ratio of sequential SAR images is proposed. Within a typical experimental area in Gongba Glacier basin，the image series of ALOS/PALSAR-1 of Japan Space Agency and Sentinel-1 A of European Space Agency are selected to carry out dynamic extraction of glacial lakes and long-term change analysis over 11 years9 time, just for validation purpose. The temporal and spatial variations of glacial lakes at the end of Gongba Glacier from 2007 to 2018 are successfully obtained. And the further analysis finds out that the volume of glacial lakes increase rapidly in the past ten years. This evidence can also confirm the current situation of aggravated melting of Gongba Glacier. In addition, the recent monitoring results in 2018 show that the expansion of local burst gushes has broken the inherent life cycle of glacial lakes，and even trigger secondary disasters of floods and debris flows. It is necessary to strengthen monitoring and prevention. [ABSTRACT FROM AUTHOR]

By using Sentinel-1 A ascending and descending synthetic aperture radar (SAR) data，this paper extracts the high-precision interferometric SAR (InSAR) coseismic deformation of the 2016 Menyuan Mw5. 9 earthquake，inverts the fault geometry and slip distribution using simplex method and nonnegative least squares method 9 and constructs the deep geometry model of regional fault zone. The results show that coseismic deformation of the Menyuan Mw5. 9 earthquake is dominated by surface uplift, and the maximums along the line-of-sight direction of ascending and descending tracks are 5. 3 cm and 7.1 cm respectively. The fault strike and dip angles are 133° and 43° respectively. The seismic slip is dominated by thrust component，mainly occurring in 6.14-12. 28 km underground. The maximum slip is about 0. 5 m, the average slip angle is 66. 85°ï¼Œand the earthquake moment is 1. 0X1018 N*m (Mw5. 94). The fitting residual root mean square of deformation observations is 0. 36 cm. The deep geometry of the regional fault zone is characterized by flower structure，which inclines to the south-west as a whole. The Menyuan earthquake rupture is a blind fault which does not appear on the surface in the flower structure. Relevant results can provide the reference for studying regional crustal movement and deformation, active fault and earthquake preparation and occurrence. [ABSTRACT FROM AUTHOR]