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Combining GPS and meteorological data to mitigate atmospheric phase in interferograms: the San Gabriel Valley, California

Gareth Funning(1), Nicolas Houlié(2) and Roland Bürgmann(2)

(1) University of California, Riverside, Geology Building, Riverside, CA 92521, United States
(2) University of California, Berkeley, 215 McCone Hall, Berkeley, CA 94720, United States


GPS and InSAR data both independently sample the troposphere state at the time of observation. Given the recent proliferation of continuous GPS sites, the use of this redundant information to characterise and remove tropospheric signals from InSAR data is becoming increasingly viable.

Here we focus on data from southern California, where a dense continuous GPS network and a diverse set of tectonic and nontectonic deformation sources make for an excellent test site. We focus on an uplift event that occurred in the San Gabriel valley, approximately 30~km NE of Los Angeles, in early 2005. Up to 6 cm of vertical deformation affecting seven GPS sites, centered on the site LONG, can be seen in both GPS and InSAR data. This has been interpreted as a hydrogeological response of an aquifer to high rainfall in the spring of 2005 by other authors (e.g. N. King et al., 2006, JGR). Here we assess the effects and potential data improvements that arise from the integration of meteorological data into our GPS processing, and hence the proportion of the InSAR signal that has a tropospheric origin.

We find that the inclusion of meteorological data in GPS data processing corrects for a persistent vertical bias in GPS station coordinates and improves the repeatability of tropospheric delay estimates. In addition, we find that the observed InSAR signal in the San Gabriel Valley spanning the period of uplift in 2005 cannot be solely interpreted as a hydrological uplift but includes significant contributions from tropospheric delay. This tropospheric phase contribution could result in an overestimate of aquifer uplift by much as 30% if left unaccounted for.


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry