The digital speckle correlation method is an important optical metrology for sur- face displacement and strain measurement.With this technique,the whole field deformation in- formation can be obtained by tracking the ...The digital speckle correlation method is an important optical metrology for sur- face displacement and strain measurement.With this technique,the whole field deformation in- formation can be obtained by tracking the geometric points on the speckle images based on a correlation-matching search technique.However,general search techniques suffer from great com- putational complexity in the processing of speckle images with large deformation and the large random errors in the processing of images of bad quality.In this paper,an advanced approach based on genetic algorithms (GA) for correlation-matching search is developed.Benefiting from the abilities of global optimum and parallelism searching of GA,this new approach can complete the correlation-matching search with less computational consumption and at high accuracy.Two experimental results from the simulated speckle images have proved the efficiency of the new approach.展开更多
Based on a study of Neoproterozoic carbonates in the Jilin-Liaoning-Xuzhou-Huaiyang area, especially its cyclic sequence stratigraphy and Sr isotopes, two maximum sea flooding events (at 820 Ma and 835 Ma) have been i...Based on a study of Neoproterozoic carbonates in the Jilin-Liaoning-Xuzhou-Huaiyang area, especially its cyclic sequence stratigraphy and Sr isotopes, two maximum sea flooding events (at 820 Ma and 835 Ma) have been identified. The resulting isochronous stratigraphic correlation proves that these Precambrian strata were connected between the Qingbaikou and the Nanhuan systems with a time range from 750 Ma to 850 Ma. The disappearance of microsparite carbonate and coming of a glacial stage offer important evidence for worldwide stratigraphic correlation and open a window for further correlation of the stratigraphic successions across the Sino-Korean and Yangtze Plates. A new correlation scheme is therefore provided based on our work.展开更多
On the basis of a one-by-one latitude-longitude grid three-dimensional seismic velocity model, the crustal P-wave velocity structure in eastern China (105-125°E and 18-41°N) is obtained, and a set of geother...On the basis of a one-by-one latitude-longitude grid three-dimensional seismic velocity model, the crustal P-wave velocity structure in eastern China (105-125°E and 18-41°N) is obtained, and a set of geotherms for each grid is established for P-T correction on P-wave velocities. The average depths of sub-crustal layers and their average P-wave velocities of 18 tectonic units in eastern China are exhibited. Our result presents a 32-34 km thick crust beneath eastern China, which is thinner than previous studies, with an average velocity of 6.54 km/s, corresponding to a 5 kg/m3 variation in crustal mean density. The thicker upper but thinner middle and lower crust results in a lower average seismic velocity of eastern China. An intermediate crustal composition with a SiO2 content of 59.7 wt% has been estimated. However, there exists a significant lateral variation in the crustal structures among the tectonic units of eastern China. The structure and composition features of some regions in eastern China indicate that extension has played an important role in the continental crust evolution of eastern China.展开更多
In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver functio...In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver function, SV-component receiver function can be obtained by directly deconvolving the P-component from the SV-component of teleseismic recordings. Our analyses indicate that the change of amplitude of SV-component receiver function against the change of epicentral distance is less than that of radial receiver function. Moreover, the waveform of SV-component receiver function is simpler than the radial receiver function and gives prominence to the PS converted phases that are the most sensitive to the shear wave velocity structure in the inversion. The synthetic tests show that the convergence of SV-component receiver function inversion is faster than that of the radial receiver function inversion. As an example, we investigate the S-wave velocity structure beneath HIA sta-tion by using the SV-component receiver function inversion method.展开更多
We propose a method to study the chaotic sys-tem for the detection of periodic signals in the presence ofstrong background noise. The numerical experiments indi-cate that the chaotic system constructed from the modifi...We propose a method to study the chaotic sys-tem for the detection of periodic signals in the presence ofstrong background noise. The numerical experiments indi-cate that the chaotic system constructed from the modified Duffing-Holmes equation is sensitive to the weak periodic signal mixed with noise, and it has certain immunity to noise. The signal to noise ratio for the system can reach to about 91 dB.展开更多
3-D structures of velocity and temperature are obtained using the data of P-wave velocity and heat flow in North China (105°E—124°E, 30°N—42°N). Taking into account the effect of three main rheol...3-D structures of velocity and temperature are obtained using the data of P-wave velocity and heat flow in North China (105°E—124°E, 30°N—42°N). Taking into account the effect of three main rheological mechanisms, namely friction sliding, brittle fracture and creep in the lithosphere, the 3-D structures of the rheological strength and viscosity in the lithosphere in North China are calculated. The results show that the strength and viscosity in the lithosphere have layering characteristics. Under the strain rate of 10?15 s?1, the upper part of the upper crust is in the brittle region and the lower part of the upper crust may be in the ductile region dominated by creep; the middle crust can be in the brittle region dominated by brittle fracture, or the upper layer of brittle fracture and lower layer of creep ductile; the lower crust almost is in the creep region dominated by creep. In addition, the strength varies horizontally, which has a close relationship with geotectonics. The influence of velocity structure and temperature structure on the rheological structure is discussed and some suggestions to improve the study of lithospheric rheological structure are put forward.展开更多
The ionospheric TEC in the sunlit boundary region during outburst of the great flare on Oct. 28, 2003 is analyzed using GPS data from IGS network. It is found that the ionosphere over the region of solar zenith angle ...The ionospheric TEC in the sunlit boundary region during outburst of the great flare on Oct. 28, 2003 is analyzed using GPS data from IGS network. It is found that the ionosphere over the region of solar zenith angle <105°was affected by this flare radiation, and the TEC enhancement decreased with the solar zenith angle. The results show that the value of TEC enhancement over the region of zenith angle ≈80° was about I0 TECU, at the terminate region (zenith angle≈90°) the TEC enhancement was about 7 TECU, and the TEC enhancement over the region of zenith angle≈110° was 1-2 TECU.展开更多
基金Project supported by the National Natural Science Foundation of China(No.19772033)the Research Innovation Fund of Tsinghua University for Ph.D.Candidates(No.092410048).
文摘The digital speckle correlation method is an important optical metrology for sur- face displacement and strain measurement.With this technique,the whole field deformation in- formation can be obtained by tracking the geometric points on the speckle images based on a correlation-matching search technique.However,general search techniques suffer from great com- putational complexity in the processing of speckle images with large deformation and the large random errors in the processing of images of bad quality.In this paper,an advanced approach based on genetic algorithms (GA) for correlation-matching search is developed.Benefiting from the abilities of global optimum and parallelism searching of GA,this new approach can complete the correlation-matching search with less computational consumption and at high accuracy.Two experimental results from the simulated speckle images have proved the efficiency of the new approach.
文摘Based on a study of Neoproterozoic carbonates in the Jilin-Liaoning-Xuzhou-Huaiyang area, especially its cyclic sequence stratigraphy and Sr isotopes, two maximum sea flooding events (at 820 Ma and 835 Ma) have been identified. The resulting isochronous stratigraphic correlation proves that these Precambrian strata were connected between the Qingbaikou and the Nanhuan systems with a time range from 750 Ma to 850 Ma. The disappearance of microsparite carbonate and coming of a glacial stage offer important evidence for worldwide stratigraphic correlation and open a window for further correlation of the stratigraphic successions across the Sino-Korean and Yangtze Plates. A new correlation scheme is therefore provided based on our work.
基金supported by grants from the National Natural Science Foundation of China(No.40104003)China Post-doctoral Science Foundationthe Chinese Academy of Sciences K.C.Wong Post-doctoral Research Award
文摘On the basis of a one-by-one latitude-longitude grid three-dimensional seismic velocity model, the crustal P-wave velocity structure in eastern China (105-125°E and 18-41°N) is obtained, and a set of geotherms for each grid is established for P-T correction on P-wave velocities. The average depths of sub-crustal layers and their average P-wave velocities of 18 tectonic units in eastern China are exhibited. Our result presents a 32-34 km thick crust beneath eastern China, which is thinner than previous studies, with an average velocity of 6.54 km/s, corresponding to a 5 kg/m3 variation in crustal mean density. The thicker upper but thinner middle and lower crust results in a lower average seismic velocity of eastern China. An intermediate crustal composition with a SiO2 content of 59.7 wt% has been estimated. However, there exists a significant lateral variation in the crustal structures among the tectonic units of eastern China. The structure and composition features of some regions in eastern China indicate that extension has played an important role in the continental crust evolution of eastern China.
基金State Key Basic Research Development and Programming Project (G199804070201) State Natural Science Foundation (40074008).
文摘In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver function, SV-component receiver function can be obtained by directly deconvolving the P-component from the SV-component of teleseismic recordings. Our analyses indicate that the change of amplitude of SV-component receiver function against the change of epicentral distance is less than that of radial receiver function. Moreover, the waveform of SV-component receiver function is simpler than the radial receiver function and gives prominence to the PS converted phases that are the most sensitive to the shear wave velocity structure in the inversion. The synthetic tests show that the convergence of SV-component receiver function inversion is faster than that of the radial receiver function inversion. As an example, we investigate the S-wave velocity structure beneath HIA sta-tion by using the SV-component receiver function inversion method.
基金the Science and Tech-nology Development Program of Jilin Province (Grant No.20020626)
文摘We propose a method to study the chaotic sys-tem for the detection of periodic signals in the presence ofstrong background noise. The numerical experiments indi-cate that the chaotic system constructed from the modified Duffing-Holmes equation is sensitive to the weak periodic signal mixed with noise, and it has certain immunity to noise. The signal to noise ratio for the system can reach to about 91 dB.
基金supported by the Project of Continental Earthquake and Forecast (Grant No. 95-13-04-06) and the National Natural Science Foundation of China (Grant No. 40174023).
文摘3-D structures of velocity and temperature are obtained using the data of P-wave velocity and heat flow in North China (105°E—124°E, 30°N—42°N). Taking into account the effect of three main rheological mechanisms, namely friction sliding, brittle fracture and creep in the lithosphere, the 3-D structures of the rheological strength and viscosity in the lithosphere in North China are calculated. The results show that the strength and viscosity in the lithosphere have layering characteristics. Under the strain rate of 10?15 s?1, the upper part of the upper crust is in the brittle region and the lower part of the upper crust may be in the ductile region dominated by creep; the middle crust can be in the brittle region dominated by brittle fracture, or the upper layer of brittle fracture and lower layer of creep ductile; the lower crust almost is in the creep region dominated by creep. In addition, the strength varies horizontally, which has a close relationship with geotectonics. The influence of velocity structure and temperature structure on the rheological structure is discussed and some suggestions to improve the study of lithospheric rheological structure are put forward.
文摘The ionospheric TEC in the sunlit boundary region during outburst of the great flare on Oct. 28, 2003 is analyzed using GPS data from IGS network. It is found that the ionosphere over the region of solar zenith angle <105°was affected by this flare radiation, and the TEC enhancement decreased with the solar zenith angle. The results show that the value of TEC enhancement over the region of zenith angle ≈80° was about I0 TECU, at the terminate region (zenith angle≈90°) the TEC enhancement was about 7 TECU, and the TEC enhancement over the region of zenith angle≈110° was 1-2 TECU.
