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Liu X.,Institute of Geology | Liu X.,Key Laboratory of Earthquake Prediction | Jiang Z.,Key Laboratory of Earthquake Prediction | Wu Y.,Key Laboratory of Earthquake Prediction
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University

In this article, we derive a spherical strain Kriging formula based on the basic theory of Kriging, and applied it to simulated and real GPS data. We analyzed its difference with the least-square collocation method. Crosscheck results indicate that Kriging interpolation is feasible and valid in GPS velocity smoothing and gridding. The Kriging strain results reveal low robustness and obvious edge effects, but the smoothed and gridded results for GPS velocity data during 1999-2004 from Kriging interpolation methods are in agreement with the results calculated by the Least-square collocation method. The strain rate results from the two methods are similar in the whole distribution characteristic, however, the kriging results show low self-consistency. In a word, the Kriging strain method is not as good as the least-square collocation method for robustness and edge effect. Source

Cao J.-L.,Key Laboratory of Earthquake Prediction | Cao J.-L.,Institute of Earthquake Science | Wang H.,Key Laboratory of Earthquake Prediction | Wang H.,Institute of Earthquake Science | And 2 more authors.

The idea of ductile flow beneath the Tibetan Plateau is widely accepted. However, there is a dispute on the way and speed of the lower crustal flow. Surface motion has direct measurements such as GPS, and mantle movement has indirect methods such as S-wave splitting. As to the lower crustal movement, there is no direct observation, so that numerical analysis is very important. In this paper, we constructed a 3-D spherical viscoe-lastic finite element model of the Tibetan Plateau to simulate the crustal flow pattern. By fitting GPS data and comparing different models, we considered that the eastward flow of the ductile lower crust in the Tibetan Plateau has been resisted by the Sichuan Basin, a channel exists in the south-eastern corner of the plateau, and similar channels of substances do not exist on the northeast corner of the plateau. The lower crust moves several milimeter faster than the upper crust, the corresponding viscosity of the lower crust was between 1018~1019 Pa · s. Source

Liu X.-K.,Key Laboratory of Earthquake Prediction | Liu X.-K.,Institute of Earthquake Science | Cui R.-S.,Key Laboratory of Earthquake Prediction | Cui R.-S.,Institute of Earthquake Science | And 4 more authors.

A method for signal detection of controlled accurate seismic source (CASS) with Wigner-Hough transformation is presented in this paper. The vibrant signal radiated by CASS and recorded by instruments at seismic stations is continuous and linearly frequency modulated(LFM), The Wigner-Ville transformation of a LFM signal is a image of time-frequency plane with a line. The Hough transformation may detect lines by integration along with them. The lines in a image become peaks in its Hough transformation image, they indicates the CASS signal existence while in detection of CASS signal. We mainly worked on the problems in applying Wigner-Hough transformation to the detection of CASS signal. The processed result of data from the experiment around Xinfengjiang reservoir in 2009 prove that this method is feasible. Source

Cao J.-L.,Key Laboratory of Earthquake Prediction | Cao J.-L.,Institute of Earthquake Science | Zhang J.,Key Laboratory of Earthquake Prediction | Zhang J.,Institute of Earthquake Science | And 4 more authors.

We constructed a 3-dimensional elastic finite element model to simulate fault deformation in the capital region of China. Firstly, we model the observed fault displacements as well as the stress field. Next we consider several possibilities and disturb the boundary constraints to predict the corresponding fault displacements. Modeling results suggest that left-lateral shear stress environment in the Zhangjiakou-Bohai zone controls fault movement in it, and it can explain the left-lateral slip of those faults in the past 40 years. When eastward pressure or southward extension are loaded, the northeast striking faults will slip dextrally. Source

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