Characteristics of Position Time Series at CORS Stations in Sichuan Basin before and after Wenchuan Earthquake

Abstract

Abstract:

The sites’ movement characteristics before and after Wenchuan Earthquake are investigated using the daily position time series of 12 continuously operating reference stations (CORS) in Sichuan Province from 2006 March to 2012 September. The displacements due to surface mass loading effects such as pressure loading, nontidal ocean loading, snow depth and soil moisture loading have been calculated and removed to reduce the root mean square (RMS) of the vertical component. A spatial filtering method based on the principle component analysis (PCA) is employed to extract the common mode errors (CME) from the daily time series. The method of maximum likelihood estimation is also utilized to choose the optimal noise model and assess the model parameters of the time series. The results indicate that the spatial response of the first principal component with the PCA analysis is reduced obviously by 20%~40% after the earthquake due to the effect of the post-seismic deformation. The velocity field has also changed obviously, especially at the PIXI, CHDU and MYAN sites, while they seem to be locked at the YAAN and QLAI sites. The annual amplitude of Sichuan Basin is the largest just one year before the earthquake, and after that it becomes smaller gradually. The results above imply that the Wenchuan Earthquake has potentially changed the movement characteristics of Sichuan Basin.

Key words: Wenchuan Earthquake, CORS, post-seismic deformation, locked

CLC Number:

References

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