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Li M.,Southwest Jiaotong University | Huang D.,Southwest Jiaotong University | Yan L.,Southwest Jiaotong University | Chen W.,Disaster Relief Research Institute | And 3 more authors.
Lecture Notes in Electrical Engineering | Year: 2014

50 HZ Global Positioning System (GPS) high rates data of 8 Continual Operation Reference System (CORS) sites nearby Lushan are used to analyze the earthquake trigger time, epicenter and magnitude. All sites position time series on N, E directions are resolved with the track software, and horizontal accuracy can reach to 2 cm at least. Horizontal position time series analyses show that the earthquake mainly affects QLAI, SCTQ, YAAN sites, the horizontal peak amplitudes can reach to 50 mm, the maximum instantaneous velocity can reach to 72.36 mm/s and the maximum instantaneous acceleration have reached to 105.9 mm/s2. Analyzing the position time series by the method of S transformation, the arrival time of seismic wave is estimated. With seismic wave arriving time and coordinates of three sites which are first detecting the seismic wave, the earthquake's epicenter and trigger time can be fast determined by three-dimensional search method. Moreover, the earthquake magnitude can also be estimated by horizontal peak amplitudes from the sites using the regression method. These suggest exiting GPS infrastructure could be developed into an effective component of earthquake assessment. © 2014 Springer-Verlag.

Li M.,Southwest Jiaotong University | Huang D.,Southwest Jiaotong University | Yan L.,Southwest Jiaotong University | Liao H.,Disaster Relief Research Institute | And 2 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2014

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.

Liao H.,Disaster Relief Research Institute | Xu R.,Disaster Relief Research Institute | Chen W.-F.,Disaster Relief Research Institute | Chen C.,Disaster Relief Research Institute | Gu T.,Disaster Relief Research Institute
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

In order to explore the long-term influence of seismic event on the GPS time series, 10 yr long processing results from Sichuan GPS network were used for the multi-parameter noise model analysis. Based on the Maximum Likelihood Estimator method and spectrum analysis, the noise components in the station coordinate time series were extracted, and through Λ-statistic test, we found 'white noise+flicker noise' is the best combination that can best fit the Sichuan local area network, meanwhile, an apparent variation in the noise component of GPS, including white noise, flicker noise, and random walk noise, occurred before and after the seismic event, which demonstrates that the traditional processing mode which simply splice and resolve the preseismic and postseismi data together is unacceptable. The common mode error analytical method and velocity variation information were all used for the initial physical interpretation of such apparent noise component change.

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