Characterizing the Seasonal Crustal Motion in Tianshan Area Using GPS, GRACE and Surface Loading Models

Yunlong Wu, Qian Zhao, Bao Zhang, Weiwei Wu
2017 Remote Sensing  
Complex tectonic and non-tectonic movements exist in the Tianshan area. However, we have not acquired good knowledge of such movements yet. In this study, we combine Global Positioning System (GPS), the Gravity Recovery and Climate Experiment (GRACE) and Surface Loading Models (SLMs) data to study the seasonal vertical crustal displacements in the Tianshan area. The results show that all three datasets exhibit significant annual variations at all 26 local GPS stations. Correlation coefficients
more » ... igher than 0.8 between the GRACE and GPS data were observed at 85% of the stations, and it became 92% when comparing GPS and SLMs. The Weighted Root Mean Squares (WRMS) reductions were 41% and 47% after removing the annual displacements of GRACE and SLMs from the GPS time series, respectively. The consistency between the GPS and SLMs data was higher than that between the GPS and GRACE data, which is mainly due to the dominant position of atmospheric loading in the study area. For the abnormal station XJYN (43 • N, 81 • E), the GPS time series showed an abnormal uplift from early 2013 to early 2015, but this not shown in the GRACE and SLMs results. We attribute this discrepancy to groundwater variations, which are not resolvable by GRACE and SLMs for small-scale regions. and Climate Experiment (GRACE) and surface loading models (SLMs) [7] [8] [9] [10] [11] . The crustal vertical deformation obtained by GRACE can be used to exclude the non-tectonic impact caused by land water storage in the GPS results. SLMs can not only remove the corresponding seasonal effect of surface loadings in the GPS results, but also provide smaller scale change information that cannot be resolved by GRACE [12] [13] [14] . The combination of GRACE and SLMs is used to remove the effect of non-tectonic seasonal signals in the GPS data, which is helpful for obtaining accurate tectonic deformation field information and other geophysical phenomena we are interested in within the target area [15] [16] [17] [18] [19] . Moreover, there are many ice sheets in the Tianshan Mountains, and the rapid warming since 1985 has resulted in sharp glacial degeneration in this area [19, 20] . Changes in the snow and ice resources in the mountains will have significant impacts on the redistribution of the terrestrial water storage and the socio-economic development of the region. Therefore, there is an exigency to study the seasonal variations in regional crustal deformation of Tianshan Mountains. The primary purpose of this study is to analyze the consistency between the seasonal vertical crustal displacements derived from GPS, GRACE and SLMs in the Tianshan area and to obtain more information on the crustal tectonic deformation field of this area. Furthermore, Singular Spectrum Analysis (SSA) was used to analyze abnormal stations to obtain important information for studying regional environmental loading changes. Data Processing and Methods GPS Data The GPS measurements used in this paper are provided by CMONOC and were collected from 26 continuous GPS stations in the Tianshan area. The data availability and locations of the GPS stations are shown in Figure 1 . All 26 continuous GPS stations contains more than five years of observations.
doi:10.3390/rs9121303 fatcat:zy57ivdesrf5xkwiygbukmseu4