Displacement Characterization and Spatial-Temporal Evolution of the 2020 Aniangzhai Landslide in Danba County Using Time-Series InSAR and Multi-Temporal Optical Dataset

On 17 June 2020, a large ancient landslide over the Aniangzhai (ANZ) slope, Danba County, Sichuan Province, China, was reactivated by a series of multiple phenomena, including debris flow triggered by heavy rainfall and flooding. In this study, Synthetic Aperture Radar (SAR) images acquired by the Sentinel-1A/B satellite and optical images captured by the PlanetScope satellites were jointly used to analyze and explore the deformation characteristics and the Spatial-Temporal evolution of the ANZ landslide before and after the multi-hazard chain. Several areas of pre-failure movements were found from the multi-temporal optical images analysis before the reactivation of the ANZ landslide. The large post-failure surface deformation over the ANZ slope was also retrieved by the optical pixel offset tracking (POT) technique. A major northwest movement with the maximum horizontal deformation of up to 14.4 m was found. A time-series InSAR technique was applied to analyze the descending and ascending Sentinel-1A/B datasets spanning from March 2018 to July 2020, showing that the maximum magnitudes of the Line of Sight (LoS) displacement velocities were −70 mm/year and 45 mm/year, respectively. The Spatial-Temporal evolution over the ANZ landslide was analyzed based on the time-series results. No obvious change in acceleration (precursory deformation) was detected before the multi-hazard chain, while clear accelerated deformation can be observed over the slope after the event. This suggested that heavy rainfall was the most significant triggering factor for the generation and reactivation of the ANZ landslide. Other preparatory factors, including the deformation behavior, the undercutting and erosion of the river and the outburst flood, the local terrain conditions, and earthquakes, might also have played an important role in the generation and reactivation of the landslide.

Processing methodology for the ITS_LIVE Sentinel-1 ice velocity product

The NASA MEaSUREs Inter-mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) project seeks to accelerate understanding of critical glaciers and ice sheet processes by providing researchers with global, low-latency, comprehensive and state-of-the-art records of surface velocities and elevations as observed from space. Here we describe the image-pair ice velocity product and processing methodology for ESA Sentinel-1 radar data. We demonstrate improvements to the core processing algorithm for dense offset tracking, “autoRIFT”, that provides finer resolution and higher accuracy data products with improved computational efficiency when compared to earlier versions. A novel calibration is applied to the data to correct for Sentinel-1A/B subswath- and full swath-dependent geolocation errors caused by systematic issues with the instruments. Sentinel-1’s C-band images are affected by variations in the total electron content of the ionosphere that results in large velocity errors in the azimuth (along-track) direction. To reduce these effects slant-range (line-of-sight or LOS) velocities are used and accompanied by LOS parameters that support map coordinate (x/y) velocity inversion from ascending and descending slant-range offset measurements, as derived from 2 image-pairs. The described product and methods comprise the MEaSUREs ITS_LIVE Sentinel-1 Image-Pair Glacier and Ice Sheet Surface Velocities: Version 2 (https://its-live.jpl.nasa.gov).

Detecting Long-Term Deformation of a Loess Landslide from the Phase and Amplitude of Satellite SAR Images: A Retrospective Analysis for the Closure of a Tunnel Event

Information about the long-term spatiotemporal evolution of landslides can improve the understanding of landslides. However, since landslide deformation characteristics differ it is difficult to monitor the entire movement of a landslide using a single method. The Interferometric Synthetic Aperture Radar (InSAR) and pixel offset tracking (POT) method can complement each other when monitoring deformation at different landslide stages. Therefore, the InSAR and improved POT method were adapted to study the pre- and post-failure surface deformation characteristics of the Gaojiawan landslide to deepen understanding of the long-term spatiotemporal evolution characteristics of landslides. The results show that the deformation displacement gradient of the Gaojiawan landslide exhibited rapid movement that exceeded the measurable limit of InSAR during the first disaster. Moreover, the Gaojiawan landslide has experienced long-term creep, and while studying the post-second landslide’s failure stability, the acceleration trend was identified via time series analysis, which can be used as a precursor signal for landslide disaster warning. Our study aims to provide scientific reference for local governments to help prevent and mitigate geological disasters in this region.

An Adaptive Offset-Tracking Method Based on Deformation Gradients and Image Noises for Mining Deformation Monitoring

The offset-tracking method (OTM) utilizing SAR image intensity can detect large deformations, which makes up for the inability of interferometric synthetic aperture radar (InSAR) technology in large mining deformation monitoring, and has been widely used. Through lots of simulation experiments, it was found that the accuracy of OTM is associated with deformation gradients and image noises in the cross-correlation window (CCW), so CCW sizes should be selected reasonably according to deformation gradients and noise levels. Based on the above conclusions, this paper proposes an adaptive CCW selection method based on deformation gradients and image noises for mining deformation monitoring, and this method considers influences of deformation gradients and image noises on deformations to select adaptive CCWs. In consideration of noise influences on offset-tracking results, smaller CCWs are selected for large deformation gradient areas, and larger CCWs are selected for small deformation gradient areas. For some special areas, special CCWs are selected for offset-tracking. The proposed method is implemented to simulation and real experiments, and the experiment results demonstrate that the proposed method with high reliability and effectiveness can significantly improve the accuracy of OTM in mining deformation monitoring.

The Surface Velocity Response of a Tropical Glacier to Intra and Inter Annual Forcing, Cordillera Blanca, Peru

We used synthetic aperture radar offset tracking to reconstruct a unique record of ice surface velocities for a 3.2 year period (15 January 2017–6 April 2020), for the Palcaraju glacier located above Laguna Palcacocha, Cordillera Blanca, Peru. Correlation and spatial cluster analysis of residuals of linear fits through cumulative velocity time series, revealed that velocity variations were controlled by the intra-annual outer tropical seasonality and inter-annual variation in Sea Surface Temperature Anomalies (SSTA), related to the El Niño Southern Oscillation (ENSO). The seasonal signal was dominant, where it was sensitive to altitude, aspect, and slope. The measured velocity variations are related to the spatial and temporal variability of the glacier’s surface energy and mass balance, meltwater production, and subglacial water pressures. Evaluation of potential ice avalanche initiation areas, using deviations from linear long-term velocity trends, which were not related to intra- or inter-annual velocities, showed no evidence of imminent avalanching ice instabilities for the observation period.

Retrieving and Verifying Three-Dimensional Surface Motion Displacement of Mountain Glacier from Sentinel-1 Imagery Using Optimized Method

The time series study of glacier movement is of special importance for rational management of freshwater resources, studying glacier evolution, understanding mechanism of glacier movement, and assessing disasters caused by glacier movement. In this paper, we put forward an optimization scheme for the shortcomings in the calculation method of using remote sensing to invert the three-dimensional (3D) surface motion displacement of glacier. The optimized method consists of Offset Tracking method, Optimizing the offset tracking results by means of iterative filtering, OT-SBAS technology and Conversion of 3D surface motion displacement of glacier. The Urumqi Glacier No. 1 was selected to test the optimized method. The 3D surface motion displacement of Urumqi Glacier No. 1 was retrieved by using the optimized method based on the ascending and descending Sentinel-1 datasets from 19 April to 29 August 2018. The distribution of 3D surface velocity of the Urumqi Glacier No. 1 was obtained in time series, and the accuracy of the inversion results was evaluated by using the field measurement data. The results show that the accuracies of the inverted displacements of east branch of Urumqi Glacier No. 1 (UG1E) were about 0.062, 0.063, and 0.152 m in the east, north and vertical directions, and these values for the west branch (UG1W) were 0.015, 0.020 and 0.026 m, respectively. It is indicated that using Sentinel-1 ascending and descending data and using the optimized method to retrieve the 3D surface motion displacement of glacier should satisfy the requirements of inversing the 3D surface motion displacement of high-latitude mountain glaciers in China.

Evaluation of ICEYE Microsatellites Sensor for Surface Motion Detection—Jakobshavn Glacier Case Study

The marine-terminating glaciers are one of the biggest contributors to global sea-level rise. Research on this aspect of the effects of global climate change is developing nowadays in several directions. One of them is monitoring of glaciers movements, especially with satellite data. In addition to well-known analyzes based on radar data from available satellites, the possibility of studying glacier displacements from new sensors, the so-called microsatellites need to be studied. The main purpose of research was evaluation of the possibility of applying new high-resolution ICEYE radar data to observe glacier motion. Stripmap High mode were used to obtain velocities for the Jakobshavn glacier with an Offset-Tracking method. Obtained results were compared with displacements obtained from the Sentinel-1 data. The comparative analysis was performed on displacements in range and azimuth directions and for maximum velocity values. Moreover, correlation plots showed that in different parts of glaciers, a comparison of obtained velocities delivers different correlation coefficients (R2) in a range from 0.52 to 0.97. The analysis showed that the scale of movements is similar from both sensors. However, Sentinel-1 data present underestimation of velocities comparing to ICEYE data. The biggest deviations between results were observed around the maximum velocities, near the Kangia Ice Fjord Bay. In the analysis the amplitude information was used as well. This research presents that data from the ICEYE microsatellites can be successfully used for monitoring glacial areas and it allows for more precise observations of displacement velocity field.

3D SAR Speckle Offset Tracking Potential for Monitoring Landfast Ice Growth and Displacement

This study investigates the growth and displacement of landfast ice along the shoreline of the Mackenzie Delta in Northwest Territories, Canada, by synthetic aperture radar (SAR) speckle offset tracking (SPO). Three-dimensional (3D) offsets were reconstructed from Sentinel-1 ascending and descending SAR images acquired on the same dates during the November 2017–April 2018 and October 2018–May 2019 annual cycles. The analysis revealed both horizontal and vertical offsets. The annual horizontal offsets of up to ~8 m are interpreted as landfast ice displacements caused by wind and ocean currents. The annual vertical offsets of approximately −1 to −2 m were observed from landfast ice, which are likely due to longer radar penetration up to the ice–water interface with increasing landfast ice thickness. Numerical ice thickness model estimates supported the conclusion that the cumulative vertical negative offsets correspond to the growth of freshwater ice. Time-series analysis showed that the significant growth and displacement of landfast ice in the Mackenzie Delta occurred between November and January during the 2017–2018 and 2018–2019 cycles.

Study of the Lange Glacier and its impact due to temperature increase in Admiralty Bay, King George Island, Antarctica

I n the western Antarctic Peninsula one of the areas the highest warming in the southern hemisphere has been identified. To characterize this tendency, we selected the Lange Glacier (LG) on King George Island, to evaluate: 1) LG surface temperature and dynamics using stakes with temperature data loggers; 2) LG submerged thickness and sea parameters through bathymetry (BT) and 29 CTD stations in front of LG; 3) glacier front (GF) using BT and a Digital Elevation Model (DEM); 4) change in GF position using DEM and historical data of GF width; 5) Calving flux (QC). Our findings showed 85 % of temperatures were above the 0 °C melting point (mean = 5.0 ± 5.2 °C). The stakes had an average ice loss of 9.3 ± 1.3 cm. The LG mean dynamics was 8.8 ± 1.5 m (0.40 ± 0.70 m/day), corroborated by Sentinel-1 satellite images (Offset Tracking = 0.43 ± 0.01 m/day). An intrusion of external waters warmer in the LG bay was identified, which destabilizes the water column due to convection processes. Our findings together indicated a continuous glacial melt that increases its dynamics due to the increase in temperature, with a contribution of fresh water to the Admiralty Bay. Based on historical results and this study, the LG retracement was estimated in 2,492 m between 1956 and 2019.