A study was made on temporal sequence of the earthquake swarm with M6. 7 which took place in Batang County, Sichuan Province, from April to Sept., 1989. Temporal sequence of the swarm was characterized by obvious sect...A study was made on temporal sequence of the earthquake swarm with M6. 7 which took place in Batang County, Sichuan Province, from April to Sept., 1989. Temporal sequence of the swarm was characterized by obvious sectional release process, in dex rise of creeping curve, certain order behavior among the peak values in the early sequence, transient tranquility before strong aftershocks and abnormal high values in sequential entropy. Subsequence of the swarm were represented by the forms of isolation pattern and mainshock-aftershock pattern,changed from the former pattern to the latter and characterized by fast-slow-fast attenuating pattern. According to time fractional dimension calculation results of the swarm sequence and the subsequences, it was discovered that non-scaling regions existed in the complicated temporal sequence structure, the span of non-scaling region of capacity dimension Do was different from that of the information dimension D1 of the same sequence, and the self-organizational features of the same sequence were different when various magnitude threshold values were selected for calculating. From the stochastic non-uniform spread of swarming high fractures in the seismic regions, it was primarily explained that the exponential attenuation of time sequence variation was likely to occur.Meanwhile, the level structures of various order sequences of the strong seismic swarm and the order problems were discussed.展开更多
We utilize the Novikov-Natterer algorithm for non-uniform attenuation to invert the backscatter projections formed by the scatter of X-rays. The backscatter signal is treated as an emitter in a non-uniformly attenuati...We utilize the Novikov-Natterer algorithm for non-uniform attenuation to invert the backscatter projections formed by the scatter of X-rays. The backscatter signal is treated as an emitter in a non-uniformly attenuating medium. This type of tomography has applications in radiology and dentistry for which metals effectively block the transmission of X-rays. Scanning for metals also has applications in security/baggage screening. The results show that when the forward scattering angle is zero, the algorithm, with a redefinition of the density function f, reduces to the PET attenuation correction.展开更多
An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth...An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth and magnitude range between 3.5 and 5.5 were analyzed to estimate the seismic quality factor Qs. A homogeneous attenuation model Qs for the wave propagation path was evaluated from spectral amplitudes, at 24 different frequencies between 0.5 and 20 Hz by using generalized inversion technique. To do this, non-parametric attenuation functions were calculated to observe spectral amplitude decay with hypocentral distance. Then, these functions were parameterized to estimate Qs. It was found that in Eastern Tohoku region, the Qs frequency dependence can be approximated with the function 33 f 1.22 within a frequency range between 0.5 and 20 Hz. However, the frequency dependence of Qs in the frequency range between 0.5 and 6 Hz is best approximated by Qs （f） = 36 f 0.94 showing relatively weaker frequency dependence as compared to the relation Qs （f） = 6 f^ 2.09 for the frequency range between 6 and 15 Hz. These results could be used to estimate source and site parameters for seismic hazard assessment in the region.展开更多
文摘A study was made on temporal sequence of the earthquake swarm with M6. 7 which took place in Batang County, Sichuan Province, from April to Sept., 1989. Temporal sequence of the swarm was characterized by obvious sectional release process, in dex rise of creeping curve, certain order behavior among the peak values in the early sequence, transient tranquility before strong aftershocks and abnormal high values in sequential entropy. Subsequence of the swarm were represented by the forms of isolation pattern and mainshock-aftershock pattern,changed from the former pattern to the latter and characterized by fast-slow-fast attenuating pattern. According to time fractional dimension calculation results of the swarm sequence and the subsequences, it was discovered that non-scaling regions existed in the complicated temporal sequence structure, the span of non-scaling region of capacity dimension Do was different from that of the information dimension D1 of the same sequence, and the self-organizational features of the same sequence were different when various magnitude threshold values were selected for calculating. From the stochastic non-uniform spread of swarming high fractures in the seismic regions, it was primarily explained that the exponential attenuation of time sequence variation was likely to occur.Meanwhile, the level structures of various order sequences of the strong seismic swarm and the order problems were discussed.
文摘We utilize the Novikov-Natterer algorithm for non-uniform attenuation to invert the backscatter projections formed by the scatter of X-rays. The backscatter signal is treated as an emitter in a non-uniformly attenuating medium. This type of tomography has applications in radiology and dentistry for which metals effectively block the transmission of X-rays. Scanning for metals also has applications in security/baggage screening. The results show that when the forward scattering angle is zero, the algorithm, with a redefinition of the density function f, reduces to the PET attenuation correction.
基金a part of author’s M.Sc Research under the project:‘‘Strengthening of Earthquake Engineering Center’’,funded by Higher Education Commission,Government of Pakistan
文摘An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth and magnitude range between 3.5 and 5.5 were analyzed to estimate the seismic quality factor Qs. A homogeneous attenuation model Qs for the wave propagation path was evaluated from spectral amplitudes, at 24 different frequencies between 0.5 and 20 Hz by using generalized inversion technique. To do this, non-parametric attenuation functions were calculated to observe spectral amplitude decay with hypocentral distance. Then, these functions were parameterized to estimate Qs. It was found that in Eastern Tohoku region, the Qs frequency dependence can be approximated with the function 33 f 1.22 within a frequency range between 0.5 and 20 Hz. However, the frequency dependence of Qs in the frequency range between 0.5 and 6 Hz is best approximated by Qs （f） = 36 f 0.94 showing relatively weaker frequency dependence as compared to the relation Qs （f） = 6 f^ 2.09 for the frequency range between 6 and 15 Hz. These results could be used to estimate source and site parameters for seismic hazard assessment in the region.
