Abstract
The spatiotemporal crustal non-tectonic deformation caused by ocean tidal loading (OTL) can reach the centimeters scale in coastal land areas. The temporal variation of the site OTL displacements can be estimated by the global positioning system (GPS) technique, but its spatial variation needs to be further determined. In this paper, in order to analyze the spatial characteristics of the OTL displacements, we propose a multi-scale decomposition method based on signal spatial characteristics to derive the OTL displacements from differential interferometric synthetic aperture radar (D-InSAR) measurements. The method was tested using long-term advanced synthetic aperture radar (ASAR) data and GPS reference site data from the Los Angeles Basin in the United States, and we compared the results with the FES2014b tide model. The experimental results showed that the spatial function of the OTL displacements in an ASAR image can be represented as a higher-order polynomial function, and the spatial trends of the OTL displacements determined by the InSAR and the GPS techniques are basically consistent with the FES2014b tide model. The root-mean-square errors of the differences between the spatial OTL displacements of these two methods and the FES2014b tide model are less than 0.8 mm. The results indicate that the OTL displacement extracted from InSAR data can accurately reflect the spatial characteristics of the OTL effect, which will help to improve the spatial resolution and accuracy of the OTL displacement in coastal areas.
Highlights
Ocean tidal loading (OTL) is the elastic response of the solid Earth to the periodic mass redistribution of the ocean, and its effect on crustal deformation gradually weakens with distance from the coast
The spatiotemporal variations of the OTL displacements can be measured by the global positioning system (GPS) technique [1,2], very long baseline interferometry (VLBI) [3], a superconducting gravimeter (SG) [4], and the interferometric synthetic aperture radar (InSAR) [5]
The OTL effect needs to be corrected in a differential InSAR interferogram due to the fact its spatial variation can reach the cm/100km scale
Summary
Ocean tidal loading (OTL) is the elastic response of the solid Earth to the periodic mass redistribution of the ocean, and its effect on crustal deformation gradually weakens with distance from the coast. The OTL effect needs to be corrected in a differential InSAR interferogram due to the fact its spatial variation can reach the cm/100km scale. Previous studies have demonstrated that OTL displacements in differential InSAR interferogram are non-linear and should be removed by the use of an ocean tide models [9,10]. The OTL effect and other large-scale signals, such as the solid Earth tidal (SET) displacement and the atmospheric delay error related to topography and orbital error, will be mixed in the differential interferogram [16,17,18,19]. The multi-scale frequency signals in the interferogram can be decomposed into sub-images with different spatial scales using 2-D wavelet decomposition, and the signal trend from near to the sea to inland can be reconstructed to obtain the higher spatial resolution OTL displacements
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