Sar Interferometry
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2021 ◽  
pp. 104088
Xiaohe Zhang ◽  
Cathleen E. Jones ◽  
Talib Oliver Cabrera ◽  
Marc Simard ◽  
Sergio Fagherazzi

2021 ◽  
Ludivine Libert ◽  
Jan Wuite ◽  
Thomas Nagler

Abstract. Monitoring the evolution of ice shelf damage such as crevasses and rifts is important for a better understanding of the mechanisms controlling the breakup of ice shelves and for improving predictions about iceberg calving and ice shelf disintegration. Nowadays, the previously existing observational gap has been reduced by the Copernicus Sentinel-1 Synthetic Aperture Radar (SAR) mission that provides a continuous coverage of the Antarctic margins with a 6 or 12-day repeat period. These unprecedented coverage and temporal sampling enable for the first time a year-round systematic monitoring of ice shelf fracturing and iceberg calving, as well as the detection of precursor signs of calving events. In this paper, a novel method based on SAR interferometry is presented for an automatic detection and delineation of active cracks on ice shelves. Active cracks cause phase discontinuities in an interferogram that are extracted automatically by applying a Canny edge detection procedure to the spatial phase gradient derived from a SAR interferogram. The potential of the proposed method is demonstrated in the case of Brunt Ice Shelf, Antarctica, using a stack of 6-day repeat Sentinel-1 interferograms acquired between September 2020 and March 2021. The full life cycle of the North Rift is monitored, including the rift detection, its propagation at rates varying between 0.35 km d−1 and 1.29 km d−1, and the final calving event that gave birth to the iceberg A74 on 26 February 2021. The automatically delineated cracks agree well with the eventual location of the ice shelf edge after the iceberg broke off. The stress field variations observed in the interferograms are attributed to a rigid-body rotation of the ice about the expanding tip of the North Rift in response to the rifting activity. The extent of the North Rift is captured by SAR interferometry well before it becomes visible in SAR backscatter images, hence highlighting the high sensitivity of SAR interferometry to small variations in the ice shelf stress field and its potential for detecting early signs of natural calving events, as well as ice shelf fracturing and damage development in response to atmospheric and oceanic warming caused by climate change.

2021 ◽  
Vol 873 (1) ◽  
pp. 012078
T P Sidiq ◽  
I Gumilar ◽  
I Meilano ◽  
H Z Abidin ◽  
H Andreas ◽  

Abstract Land Subsidence became recent issue in environmental management in Indonesia. Large cities in Indonesia, especially in Java Island, are well known to suffer from fast rate land subsidence such as Jakarta, Bandung, and Semarang. However, the phenomena is presumed to also happen in other cities which have large industries and located on the deposit or clay soil layer. The effect of land subsidence may be different in some location, but the coastal zone will have more impact since land subsidence will also induce tidal flood and may cause land area reduction. In this study, we use more than 70 Sentinel-1 data, range from year 2016 to 2020 to map the land subsidence in the Java North Coast. The interferograms are selected based on Small Baseline Subset (SBAS) algorithm. National Digital Elevation Model (DEMNAS) is used in differential InSAR process. Our result shows that many cities along the Java North Coast suffer land subsidence. Jakarta, experience has maximum subsidence more than 5 cm/year. In Central Java, Pekalongan experience up to 7 cm/year of land subsidence, while Semarang and Demak has subsidence rate up to 8 cm/year.

2021 ◽  
Vol 42 (18) ◽  
pp. 7101-7113
Huiqiang Wang ◽  
Jianjun Zhu ◽  
Haiqiang Fu ◽  
Yanan Yu

2021 ◽  
Vol 21 (8) ◽  
pp. 2285-2297
Xuguo Shi ◽  
Shaocheng Zhang ◽  
Mi Jiang ◽  
Yuanyuan Pei ◽  
Tengteng Qu ◽  

Abstract. Ground subsidence is regarded as one of the most common geohazards, accompanied with the rapid urban expansion in recent years. In the last 2 decades, Wuhan, located in the alluvial Jianghan Plain, has experienced great urban expansion with increased subsidence issues, i.e., soft foundation subsidence and karst collapse. Here we investigated subsidence rates in Wuhan with 2015–2019 Sentinel-1 synthetic aperture radar (SAR) images. We found that the overall subsidence over the Wuhan region is significantly correlated with the distribution of engineering geological subregions (EGSs). We further validated the interferometric SAR (InSAR) measurements with better than 5 mm accuracy by comparing with leveling measurements. Subsidence centers in Qingling–Jiangdi, Houhu, Qingshan, and Dongxihu were identified with displacement rates of approximately 30 mm/yr. Our results demonstrated that the dominant driving factor is ongoing construction, and the fact that the subsidence centers shifted with construction intensities. The Qingling–Jiangdi area in our study is a well-known site of karst collapse. We find that the nonlinear subsidence of this area is correlated with the seasonal rainfall.

Valerio Gagliardi ◽  
Luca Bianchini Ciampoli ◽  
Fabrizio D'Amico ◽  
Amir M. Alani ◽  
Fabio Tosti ◽  

Lisa Beccaro ◽  
Cristiano Tolomei ◽  
Claudia Spinetti ◽  
Marina Bisson ◽  
Laura Colini ◽  

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