Investigating the Ground Deformation and Source Model of the Yangbajing Geothermal Field in Tibet, China with the WLS InSAR Technique

Abstract

Abstract:Ground deformation contains important information that can be exploited to look into the dynamics of a geothermal system. In recent years, InSAR has manifested its strong power in the monitoring of ground deformation. In this paper, a multi-temporal InSAR algorithm, WLS InSAR, is employed to monitor and characterize the Yangbajing geothermal field in Tibet, China, using 51 ENVISAT/ASAR images acquired from two overlapping descending tracks. The results reveal that the WLS InSAR algorithm can suppress the adverse effects of seasonal oscillations, associated with the freezing-thawing cycle of the permafrost in the Qinghai-Tibet Plateau. Deformations of up to 2 cm/yr resulting from the exploitation of the geothermal resource have been detected in the southern part of the Yangbajing field between 2006 and 2010. A source model inversion of the subsurface geothermal fluids was carried out based on the elastic half-space theory using the accumulated deformations. It was found that most geothermal fluid loss has occurred in the southern part of the shallow reservoir as the pore space beneath the northern part of field was recharged by the ascending flow from the deep layers of the reservoir through well-developed faults in the region.

Deriving 3-D Time-Series Ground Deformations Induced by Underground Fluid Flows with InSAR: Case Study of Sebei Gas Fields, China

“…This means a relationship between the underground fluids volume changes and the 3-D surface deformations [1,40,79,80]: Two-pass D-InSAR was employed to process the 64 interferograms. The~30 m resolution SRTM DEM was utilized to remove the topographic phase in the interferograms.…”

“…Following that, a polynomial model was applied to mitigate the orbit errors. Finally, the WLS InSAR algorithm was employed to retrieve the LOS time-series deformation measurements [40]. Since the study area is relatively flat and far away from the coastline, and the climate is quite dry, the atmospheric artifacts basically are absent in the interferograms [77,78], and thus were ignored in the WLS InSAR processing.…”

“…This means a relationship between the underground fluids volume changes and the 3-D surface deformations [1,40,79,80]:…”

“…MT-InSAR has been successfully and extensively used in monitoring the deformations Remote Sens. 2017, 9, 1129 2 of 22 induced by exploitation of underground fluids, such as groundwater [7,[14][15][16][17][18][19][20][21], oil [22][23][24][25][26][27][28][29][30][31], natural gas [14,30,[32][33][34][35][36][37], and geothermal [38][39][40][41][42][43][44][45], because of its low cost, wide spatial coverage, high measurement precision, and fine spatial resolution. However, MT-InSAR can capture only one-dimensional (1-D) time-series deformation that includes the sum of projections on the line-of-sight (LOS) direction of actual 3-D time series ground deformations.…”

“…This provides a great potential for resolving 3-D time series deformations induced by underground fluid flows with InSAR. In this study, the method is extended to the temporal domain by the 1-D time series deformation measurements from weight least square (WLS) InSAR algorithm [40], and applied for the first time to investigate the 3-D time series deformation over the Sebei gas field in Qinghai, China, with 37 Sentinel-1 images acquired during October 2014-July Remote Sens. 2017, 9, 1129 3 of 22 2017.…”