Exploring GRACE and GPS and Absolute Gravity Data on the Relationship Between Hydrological Changes and Vertical Crustal Deformation in South India

Rainfall during the monsoon across the Indian subcontinent leads to significant hydrological changes that alter the ground over a range of timescales. In the present study, both GPS and Grace data have been analysed to assess the impact of groundwater variability on ground deformation study region. The amplitudes seasonal vertical deformation phases estimated from Global Positioning System (GPS) and Gravity Recovery and Climate Experiment (GRACE) are reliable, demonstrating that hydrological factors are the main contributors of periodic deformation in the region. We compare the deformation computed from GRACE mass signal with that of altitude variations from non-stop GPS data from three locations, viz. Bangalore, Hyderabad and Lucknow. For the specified period of time, the patterns of the GRACE and GPS plots match well for Hyderabad and Bangalore but not so well for Lucknow. This shows that hydrological loading is mostly to blame for the crustal deformation seen by GPS in Hyderabad and Lucknow. The crustal deformation as determined by the GPS in Lucknow is consistent with that derived from GRACE data over Lucknow to some extent. This shows that GRACE may be used to adjust the deformation detected by GPS for the hydrological effect.