InSAR observations and modeling of Earth surface displacements in the Yellow River Delta (China)

Liu, Peng (2012) InSAR observations and modeling of Earth surface displacements in the Yellow River Delta (China). PhD thesis, University of Glasgow.

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Subsidence in river deltas is a complex process that has both natural and human causes (Boesch et al., 1994). The Yellow River delta is used for farming, contains an important nature reserve for wild animals especially for waterfowl, has a population of 1.64 million, and is the location of significant oil fields (Chen et al., 2012). Increasing human activities like farming and petroleum extraction are affecting the Yellow River delta, and one consequence is subsidence. This subsidence may have social, economic and environmental impacts (Syvitski et al., 2009). The purpose of this thesis is to measure the surface displacement in Yellow River delta and to investigate the causes of measured displacement.
The use of Interferometric Synthetic Aperture Radar (InSAR) for Earth surface displacement mapping has increased since the 1990s when a lot of radar images become available. InSAR time series techniques identify displacement of an area between different image acquisition times. In this study, StaMPS package was employed to process Envisat ASAR images collected between 2007 and 2010. StaMPS selects only the stable pixels from interferograms to maintain the coherence signals over a long time interval. Consistent results between two descending tracks show subsidence with a mean velocity of up to 30 mm/yr in the radar line of sight direction in Gudao Town (oilfield), Gudong oilfield and Xianhe Town of the delta, and also show that subsidence is not uniform across the delta. Field investigation shows an association between areas of subsidence and of petroleum extraction.
In a 9 km2 area of the Gu-Dao Oilfield in the delta, InSAR derived surface deformation is used to model the geometry, volume or pressure change of the deformation source, namely the extraction of fluids, using three different models: the spherical source Mogi type model, the finite prolate spheroid model and the poroelastic disk reservoir model. In general, good fits between InSAR observations and modelled displacements are seen. The source depths estimated in the three models agree well with the published oilfield depth. The subsidence observed in the vicinity of the oilfield is thus suggested to be caused by fluid extraction.
For Mogi type model, a uniform subsidence rate of about 7 mm/yr is co-estimated. InSAR observations in Xianhe Town in the delta, which is not affected by oil extraction, also
shows 8~12 mm/yr uniform subsidence. It is suggested this uniform subsidence is caused by other sources e.g. loading and sediment compaction. Since InSAR only measures relative displacement, accurate determination of small uniform rate need the reference phase provided by other observations e.g. GPS and levelling.
Mogi model provides the volume change in Gudao oilfield. The ellipsoidal source and the disk reservoir model the pressure changes. Additional reservoir information e.g. material parameter will help better confine the model parameters. Although no production data is available for comparison, the volume and pressure changes obtained from the models, together with InSAR observed displacement might be of interest for oil industry, to predict future subsidence in Gudao oilfield.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: InSAR, SBAS, Yellow River delta, subsidence, model, poroelastic, Mogi, ellipsoidal source, disk reservoir, inversion
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
G Geography. Anthropology. Recreation > GA Mathematical geography. Cartography
G Geography. Anthropology. Recreation > GB Physical geography
Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
Supervisor's Name: Li, Dr. Zhenhong and Hoey, Prof. Trevor
Date of Award: 2012
Depositing User: Dr Peng Liu
Unique ID: glathesis:2012-3787
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 07 Dec 2012
Last Modified: 21 Dec 2012 12:08

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