Identification of Glacial Isostatic Adjustment in Eastern Canada Using S Transform Filtering of GPS Observations
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Over the years, a number of different models and techniques have been proposed to both quantify and explain the glacial isostatic adjustment (GIA) process. There are serious challenges, however, to obtaining accurate results from measurements, due to noise in the data and the long periods of time necessary to identify the relatively small-magnitude signal in certain regions. The primary difficulty, in general, is that most of the geophysical signals that occur in addition to GIA are nonstationary in nature. These signals are also corrupted by random as well as correlated noise added during data acquisition. The nonstationary characteristic of the data makes it difficult for traditional frequency-domain denoising approaches to be effective. Time–frequency filters present a more robust and reliable alternative to deal with this problem. This paper proposes an extended S transform filtering approach to separate the various signals and isolate that associated with GIA. Continuous global positioning system (GPS) data from eastern Canada for the period from June 2001 to June 2006 are analyzed here, and the vertical velocities computed after filtering are consistent with the GIA models put forward by other researchers.
KeywordsPostglacial rebound glacial isostatic adjustment S transform time–frequency filtering continuous GPS
The authors would like to place on record their sincere gratitude to the Department of Foreign Affairs and International Trade (DFAIT), Canada, the University of Western Ontario, Canada, and the National Institute of Technology, Rourkela, India for facilitating this project. The work of K.F.T. was supported by an NSERC Discovery Grant and the NSERC and ICLR/Aon Benfield Industrial Research Chair. GPS data were provided by Natural Resources Canada and Quebec Ministère des Ressources Naturelles. Images were plotted with the help of GMT software developed and supported by Paul Wessel and Walter H.F. Smith.
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