Acknowledgment:
Authors acknowledge the GPS data provided by International GNSS Network (IGS) (ftp://cddis.gsfc.nasa.gov), and UNAVCO (ftp://data-out.unavco.org/), CORS (https://geodesy.noaa.gov/CORS/). We thank IGS and CODE for providing GPS products. We also thank Cornell University for sharing COMCOT. KS acknowledges the financial support of CSIR for SRF fellowship (No.31/66(001)/2017-EMR-I dt:28/03/17) and AcSIR for their support. Both the authors profoundly thank the insightful reviews of the two anonymous reviewers and acknowledge their valuable comments which helped to improve the paper significantly.