HR: 10:20h
AN: G51C-01 INVITED     [PDF]
TI: Seasonal Crustal Deformation in Japan and its Interannual Variation
AU: * Heki, K
EM: heki@miz.nao.ac.jp
AF: Div. Earth Rotation, National Astron. Obs., 2-12 Hoshigaoka, Mizusawa-city, Iwate, 023-0861 Japan
AB: A dense array of GPS is useful to study seasonally changing load through periodic components in crustal movements. In this paper I review observed and predicted seasonal crustal movements in the Japanese Islands, where both nationwide dense GPS array and meteorological sensor network are available. From comprehensive evaluation of various sources contributing to seasonal signals, the largest factor in Japan is found to be snow, weighing over 1000 kg per square meter in some regions. This is followed by various kinds of loads on the land area, such as atmosphere, soil moisture and dam, and non-tidal ocean loads also cause certain seasonal signatures. Seasonal crustal deformations are calculated by synthesizing all these seasonal load changes, some of which are directly measured meteorologically and others are inferred through models. They are compared with real data observed by the dense GPS array in Japan, and they agreed fairly well. The seasonal signals observed by GPS also include artifacts, such as scale changes due possibly to atmospheric refraction, and atmospheric delay gradients. We often discuss subtle crustal deformation signals, e.g. those associated with silent earthquakes, isolating them by removing secular and periodic components. Understanding seasonal signals and their interannual variability is crucial in removing these unwanted signals. Amplitudes of seasonal signals in Japan were suggested to have increased in 2000, and I discuss its causal relationship with the increase in snow depths in the 1999/2000 winter.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1243 Space geodetic surveys
DE: 1247 Terrestrial reference systems
DE: 1863 Snow and ice (1827)
DE: 1866 Soil moisture
SC: Geodesy [G]
MN: 2003 Fall Meeting