Seasonal Variations in Hydrological Influences on Gravity Measurements Using gPhones

  • Author(s): Kaixuan Kang, Hui Li, Peng Peng, Hongtao Hao, and Jin Wei
  • DOI: 10.3319/TAO.2010.08.02.01(TibXS)
  • Keywords: Gravity, Gravimeter, gPhone, Hydrologic loading
  • Citation: Kang, K., H. Li, P. Peng, H. Hao, and J. Wei, 2011: Seasonal variations in hydrological influences on gravity measurements using gPhones. Terr. Atmos. Ocean. Sci., 22, 157-168, doi: 10.3319/TAO.2010.08.02.01(TibXS)

Hydrological influences on a local gravity field may reach amplitudes on the order of 10 microgals. Since 2007, fifteen Microg LaCoste gPhones have been successively installed in gravity stations in China. The outputs from gPhones include ten data channels with second sampling such as raw gravity, corrected gravity, long level data and cross level data, ambient and sensor temperature, ambient and sensor pressure, and others. In this study, we select six stations in northwest China (GaoTai, LaSa, LanZhou, ShiQuanHe, WuShi, XiAn) and one station in the northeast (HaiLaEr). We have modeled the major tides (earth solid tide, ocean tide and pole tide), corrected for atmospheric loading effects using local measurements, fitted instrumental drift using segmental fitting based on the distinct characteristics of gravimeter drift, and ultimately obtained the monthly residual gravity with amplitudes of 10 ~ 20 microgals. We find that the results obtained by the gravimeter for those stations with stable conditions and no large disturbances are obviously correlated with hydrologic loading as modeled by the Global Land Data Assimilation System and Climate Prediction Center. We also notice that at some stations there are obvious phase lags with a period of three months or more between the residual gravity and the influence of hydrological loading. These large discrepancies may be associated with local hydrologic effects, local topography or some other complex tectonic movement and geodynamical mechanism, which were not considered in this paper.

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