Surface Deformation of Xiamen, China Measured by Time-Series InSAR
Abstract
:1. Introduction
2. Study Area and Data
2.1. Study Area
2.2. Data
3. Methods
3.1. PS-InSAR Technique
3.2. PS-InSAR Data Processing
- (1).
- Data preprocessing: We used precise orbit data to correct the orbit information of the original SAR images, and then converted them into SLCs. They were clipped with the study area (.shp) file.
- (2).
- Generation of the interferometric pair connection graph: We selected the image on 1 September 2020 as the super-master image. According to the set critical baseline threshold, 80 SLCs were processed to generate the interferometric pair connection graph (Figure 3).
- (3).
- Interferometric workflow: According to the connection relationship of the interferometric pairs, we performed interferometric workflow processing for each pair of images, mainly including image registration, generation of the interferogram, flattening of the interferogram using the external DEM, and calculation of the amplitude dispersion index. The interferogram at each time point was finally obtained.
- (4).
- First inversion: Based on the identification of a certain number of permanent scatterers, we focused on analyzing the historical phases of these reliable single targets for the first linear model inversion to obtain the displacement rate and residual topography. Then, the synthesized interferogram were flattened.
- (5).
- Second inversion: Based on the result of the first inversion, the atmospheric phase was estimated and removed to obtain the final deformation rate.
- (6).
- Geocoding: The coherence coefficient threshold was set to 0.9. All PS processing results, including the deformation rate, height residual, deformation sequence, KML, vector file, etc., were projected into the map system.
3.3. SBAS-InSAR Technique
3.4. SBAS-InSAR Data Processing
- (1).
- Data preprocessing: We used precise orbit data to correct the orbit information of the original SAR images, and then converted them into SLCs. They were clipped with the study area (.shp) file.
- (2).
- Generation of the interferometric pair connection graph: We conducted interferometric pair matching processing for 80 SAR images. The maximum percentage of the critical baseline was set to 45%, and the maximum time baseline was set to 365 days. We selected the image on 8 June 2018 as the super-master image and optimally combined all the images to form a short baseline set (Figure 4).
- (3).
- Interferometric workflow: We successively conducted interferometric processing on all the pairs in the connection graph, including SLC images pair registration, interferogram generation, flattening the terrain using the external DEM and the terrain phase, differential interferogram filtering, coherence calculation, and phase unwrapping. The threshold of the unwrapping correlation coefficient was set to 0.2. The interferogram, coherence graph, and phase unwrapping graph were finally generated.
- (4).
- Orbit refinement and reflattening: We selected the graphs from (3) with high coherence, good unwrapping, and no deformation and residual terrain fringes. The stable areas far away from the deformation were used as ground control points (GCPs) for orbit refinement and reflattening, which were used to estimate and remove the residual constant phase and the phase ramp that still exists after unwrapping.
- (5).
- First inversion: Firstly, the unwrapped phase was optimized and reflattened. Secondly, based on the orbit refinement and reflattening, we used the SVD algorithm to estimate the deformation rate and the residual topography. Finally, we conducted a secondary unwrapping to obtain the preliminary deformation rate.
- (6).
- Second inversion: On the basis of the deformation rate obtained from the first inversion, we conducted phase optimization, reflattening, and atmospheric filtering. Then, the atmospheric phase was estimated and removed to obtain more accurate displacement.
- (7).
- Geocoding: We performed geocoding on the results of the second inversion of SBAS to obtain the surface deformation results in the line of sight (LOS) direction.
4. Results
4.1. Comparison of PS and SBAS Monitoring Results
4.1.1. Histograms
4.1.2. Deformation Zones
4.1.3. Correlation of Homonymous Points
4.2. Definition of Typical Subsidence Zones
5. Discussion
5.1. Impact of Groundwater Extraction on Land Subsidence
5.2. Impact of Geological Structure on Land Subsidence
5.3. Impact of Land Reclamation on Land Subsidence
5.4. Impact of Engineering Construction on Land Subsidence
6. Conclusions
- (1).
- Although the SBAS technique and the PS technique exhibit strong consistency, the SBAS technique exhibits stronger coherence, making it more advantageous for monitoring surface deformation in Xiamen.
- (2).
- Typical subsidence zones in Xiamen include the Yuanhai Terminal and Maluan Bay in Haicang District, Xitang and Guanxun in Tong’an District, Jiuxi entrance in the southern part of Xiang’an District, Yangtang on Dadeng Island in Xiang’an District, the southeastern part of Dadeng Island in Xiang’an District, and Yundang Lake in Siming District. These areas require special attention for the prevention and mitigation of geological hazards.
- (3).
- This study investigates the spatial and temporal drivers of land subsidence in Xiamen by analyzing four factors that influence land subsidence, in conjunction with the identified typical subsidence zones and their respective long-term time series. Geological structure, particularly in fault zones and seismic focus areas, significantly influence subsidence. Increased groundwater extraction is another significant contributor to land subsidence. Land subsidence is particularly pronounced in reclaimed areas during the initial phase, the consolidation process, and following land compaction. Construction activities alter soil structure and new structures increase the likelihood of land subsidence.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Data | Timespan | Quantities | Unit | Data Sources |
---|---|---|---|---|
Sentinel-1A image | May 2017 to December 2023 | 80 | view | ASF Data Search (https://search.asf.alaska.edu (accessed on 1 December 2023)) |
DEM | — | — | m | Geospatial Data Cloud (https://www.gscloud.cn/home (accessed on 15 December 2023)) |
Precision orbit | May 2017 to December 2023 | 80 | — | https://s1qc.asf.alaska.edu/aux_poeorb (accessed on 2 December 2023)) |
Fault belt | — | 23 | — | Earthquake Safety Island |
Seismic focus | January 1971 to December 2023 | 93 | — | Earthquake Safety Island |
Precipitation | May 2017 to December 2023 | 80 × 4 | mm | XMWCB (http://112.48.134.86:9003/vs4y (accessed on 1 March 2024)) |
Reservoir level | May 2017 to December 2023 | 80 × 4 | m | XMWCB (http://112.48.134.86:9003/vs4y (accessed on 3 March 2024)) |
Groundwater | 2017 to 2022 | 6 × 2 | 108 m3 | Xiamen Water Resources Bulletin from 2017 to 2022 |
Zones | Municipal Districts | PS | Velocity [Mode] (mm/yr) | SBAS | Velocity [Mode] (mm/yr) |
---|---|---|---|---|---|
Maluan Bay | Haicang | −11.04~2.40 [0.43] | −16.35~6.29 [0.48] | ||
Xitang | Tong’an | −17.58~2.01 [0.49] | −18.16~2.73 [0.51] | ||
Dadeng Island | Xiang’an | −15.19~3.07 [−1.23] | −23.93~10.92 [−1.10] | ||
Shihushan Terminal | Huli | −7.38~2.03 [0.86] | −7.86~4.76 [0.87] | ||
Yundang Lake | Siming | −10.85~3.00 [1.23] | −11.18~4.41 [1.20] |
Serial Number | Typical Subsidence Zone | Engineering Construction |
---|---|---|
A | Yuanhai Terminal in Haicang District | On 28 September 2020, Xiamen Yuanhai Terminal railway line officially started construction, and is expected to be completed and opened to traffic in early 2024. |
B | Maluan Bay in Haicang District | (1) From 1 January 2016 to 17 November 2017, the Maluan Bay section of Metro Line 2 was under construction. (2) From 30 December 2016 to 21 November 2018, the Maluan Bay section of Metro Line 6 was under construction. (3) Metro Line 4 is under construction. |
C | Xitang in Tong’an District | From October 2015 to May 2021, the Tonglen Road improvement project was underway. |
D | Guanxun in Tong’an District | (1) Haixiang Avenue is under construction. (2) Metro Line 4 is under construction. |
E1 | Jiuxi entrance in the southern part of Xiang’an District | (1) From March 2019 to October 2021, Jiuxi Bridge was under construction. (2) From 2019 to 20 April 2023, the Xidong Bridge was under construction. |
E2 | Yangtang in the southern part of Xiang’an District | (1) From August 2004 to August 2018, Dadeng Bridge was under construction. (2) From February 2022 to November 2023, Dadeng Bridge was under an upgrading project. (3)The latter part of Metro Line 3 is under construction. (4) Metro Line 4 is under construction. |
F | The southeastern part of Dadeng Island in Xiang’an District | On 4 January 2022, the full construction of Xiang’an International Airport began, which is expected to open in 2026. |
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He, Y.; Qian, Z.; Chen, B.; Yang, W.; Hao, P. Surface Deformation of Xiamen, China Measured by Time-Series InSAR. Sensors 2024, 24, 5329. https://doi.org/10.3390/s24165329
He Y, Qian Z, Chen B, Yang W, Hao P. Surface Deformation of Xiamen, China Measured by Time-Series InSAR. Sensors. 2024; 24(16):5329. https://doi.org/10.3390/s24165329
Chicago/Turabian StyleHe, Yuanrong, Zhiheng Qian, Bingning Chen, Weijie Yang, and Panlin Hao. 2024. "Surface Deformation of Xiamen, China Measured by Time-Series InSAR" Sensors 24, no. 16: 5329. https://doi.org/10.3390/s24165329