ERS and ENVISAT multitemporal interferometric analisys to characterise land subsidence and uplift in Phoenix (Arizona)
23-Sep-2017 UT
In this study the team show the usefulness of InSAR for examining surface deformation due to groundwater withdrawal and recharge in Phoenix, Arizona. Multi-track ascending and descending ERS SAR datasets from 1992-1996 and ENVISAT ASAR , 2003-2010 are combined to obtain vertical and horizontal (east-west) displacement time series components.

The LOS time series of surface deformation are inverted to obtain spatiotemporal maps of the vertical and horizontal deformation fields. The analysis shows that the general deformation pattern is consistent among datasets and is characterised by three zones of subsidence and a broad zone of uplift. In situ independent hydraulic head data from observation wells were also provided by Arizona Department of Water Resources (ADWR) and are used in the validation and to form a time series at 33 locations in the Phoenix metropolitan area.

Continuous wavelet transform is applied to the time series of vertical surface deformation data and hydraulic head levels to construct the time-frequency representation of the signal and separate periodic signal components and the long-term trend. The availability of both components at selected period durations allows for the estimation of mechanical properties of the aquifer system. In particular the isolated signal components are used to estimate the elastic storage coefficient, the inelastic skeletal storage coefficient, and the compaction time constant.Together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation.

Understanding aquifer parameters is useful for the on-going management of groundwater resources and ,effective urban planning in an expanding metropolis and in general improving understanding of the source and mechanisms of subsidence which is important for modelling and risk management.

The result has been presented in the paper "Spatiotemporal characterization of land subsidence and uplift in Phoenix using InSAR time series and wavelet transforms", authored by Megan Miller and Manoochehr Shirzaei,, and published in July 2015 in the JOURNAL OF GEOPHYSICAL RESEARCH - Solid Earth doi:DOI: 10.1002/2015JB012017, 2015.