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Huang J.,Lanzhou Institute of Seismology | Wan Y.-G.,China Institute of Technology
Earthquake | Year: 2015

The capital region of China emplaces dense seismic network in recent years, it is possible to solve small focal mechanisms. We gathered large earthquake focal mechanisms in last fifty years and moderate or small earthquake focal mechanisms between 2002 and 2004, and calculated the present tectonic stress field of the capital region by the grid search method, which weighs different sized earthquakes and can improve the accuracy of the stress field inversion. The analysis of inversion results of different sub-region show that the direction of the maximum principle compressive stress axe is toward N (43°~86°) E in the Beijing-Zhangjiakou-Datong region, toward N (38°~86°) E in Tangshan area, and toward N (79°~81°) E in Xingtai area. Inversion results of this paper are similar with previous results, and reflect the correctness of the approach. The results reveal the stress field distribution consistency and sub-region difference in the capital region, and can provide reference for earthquake mechanism explanation and geodynamics research. ©, Science Press. All right reserved.

Jia G.,Shanxi University | Yuan Z.,Lanzhou University of Technology | Yuan Z.,Lanzhou Institute of Seismology
World Information on Earthquake Engineering | Year: 2013

It is found that rural self-built masonry houses usually do not adopt details of seismic design, or complete seismic measures. Aimed at studying some new anti-seismic technologies for rural self-built masonry houses, finite element models of three masonry walls that adopt concealed structural column were developed, nonlinear responses of three models were simulated under low cyclic loading, and seismic behavior of three walls were analyzed by using ANSYS. The results indicate that the maximum displacement of the masonry walls with concealed structural column decreases 33%-50% and the major principal stress is increased by 164%-385% than the masonry walls with no seismic measures. Concealed structural column is capable of enhancing strength, stiffness and deformability of masonry walls, and consuming the earthquake energy under seismic action. Because of simple formation, convenient construction and saving material, concealed structural column can be considered as a kind of effective seismic measures for rural self-built masonry house.

Wu Z.-J.,China Earthquake Administration | Wu Z.-J.,Lanzhou Institute of Seismology | Chen T.,Chinese Academy of Sciences | Ma W.,Chinese Academy of Sciences
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The dry bridge, named bridge instead of embankment, has been widely adopted in regions with high temperature and instable permafrost or those with high ice content permafrost along the Qinghai-Tibet railroad. In order to obtain the dynamic response characteristics of typical embankments and dry bridges under the effect of vibration loads of trains in permafrost regions, strong motion tests on the filld embankment at the Beilu River segment and the bridge pile foundation of the Qingshui river Bridge in permafrost regions are carried out. The acceleration waveforms under running of freight and passenger trains are acquired from the tests, and the attenuation laws of vibration response, energy of vibration response and natural frequency are obtained by analyzing the acceleration response and FFT spectrum response. The test results show that there is an obvious damping effect during the transfer process. This study is of great significance to the stability analysis and prediction of the Qinghai-Tibet railroad.

Zhang H.,Lanzhou Institute of Seismology | Zhang L.-P.,Institute of Earthquake Science | Feng J.-G.,Lanzhou Institute of Seismology
Earthquake | Year: 2014

For the Minxian-Zhangxian MS6.6 earthquake sequence of July 22, 2013, we invert focal mechanism solutions of the mainshock event and some strong aftershocks in the sequence using the CAP (Cut and Paste)method and broadband waveforms recorded by the Tenth five-year digital seismic network. The result shows that the best double solution of the MS6.6 mainshock is 189°, 51° and 142° for strike, dip and rake angles respectively, the other nodal plane is 305°, 61° and 46°; the character of the mainshock shows thrust with a small strike-slip component and the focal depth of the mainshock is 7 km. The advantage angel of the nodal plane II which is in the NE direction of the focal mechanism solutions of 8 aftershock events is about 52°, which shows the characteristics of large thrust components. The nodal plane II has been identified to be representative of the seismogenic fault plane of the event in consideration of the local active geologic structure, the distributions of the aftershocks and the seismic intensities. The characteristics of the focal mechanism of earthquake sequence are similar with the Lintan-Tanchang fault. In conclusion, the occurrence of the Minxian-Zhangxian MS6.6 earthquake may correlated with activities of the Lintan-Tanchang fault.

Chen W.-K.,Lanzhou Institute of Seismology | Chen W.-K.,Chinese Academy of Sciences | He S.-L.,Lanzhou Institute of Seismology | Pei H.-J.,Chinese Academy of Sciences | And 2 more authors.
Earthquake | Year: 2013

Using the modified local variance method based on different sizes of calculation window, we determine objects after earthquake such as damaged building, intact buildings. By conducting a series of experimental analysis on the aerial and Quickbird image, we obtain that on the Quickbird image the optimal spatial resolution of intact urban buildings is about 2 ~ 3 m and the damage buildings is 2 ~ 4 m, on the aerial image the optimal spatial resolution of intact urban buildings is about 3 ~ 4 m. The optimal spatial resolution is closely related to the size of the object on the ground. And objects of different sizes have different optimal spatial scale. While processing a large amount of images with high spatial resolution, we choose the optimal spatial scale through resampling. This method can effectively reduce the calculational time on the image and is theoretically meaningful for the application of remote sensing technology to fast assessment of earthquake disaster.

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