The Processes And Analysis Of The Microseisms Records In Fujian Region

At present, the microseisms are paid attention to more people because of its special characteristics despite it is tiny and can be observed everywhere at any moment. In this paper, the current research of the microseisms is briefly summarized and the microseisms recorded by the Seismic Monitoring Network of Fujian province from May 1,2005 to August 12,2006 is mainly researched.The main achievements of this study have been summarized as follows:1. The microseisms recorded by the Seismic Monitoring Network of Fujian province from May 1, 2005 to August 12, 2006 is utilized to analyse the law of the root-mean-square velocity and the predominate frequency changes with the time and the space. The result shows that the changes of the root-mean-square velocity from the wide-broadband velocity records is in of accord with each other. The microseisms' amplitudes recorded by the inshore station are larger than those recorded by the inland station and get large when the storm comes. The predominate frequency whose changes is in of accord with each other is between 0.2-0.4Hz and get down when the storm comes. Finally the paper studies on the connection between the change of the root-mean-square and the occur of the earthquake. It can be seen that there is no obvious relationship between them.2. The strengthen microseism signals, the amplitude of the microseisms are different from the daily noise remarkbly when the storm occurred maybe reflect the relationship of the microseisms characteristics. Therefore the microseism recorded by the Seismic Monitoring Network of Fujian province during August 2006 when the Saomai storm came is investigated. It indicate that there is corking correlativity between the horizontal microseisms and the vertical microseisms and the correlative coefficient can even exceed 0.8 sometimes. Furthermore, the vertical microseisms is anterior to the horizontal microseisms and the phase difference isπ/2. The particle on the surface of the earth removed as a counter-clockwise ellipse when the microseisms transmit. The ratio of the amplitude of the microseisms on the horizontal and on the vertical is about 0.7 in [0.1,0.5]Hz band. Therefore, we think the main component of microseisms is rayleigh waves. 3. According to the method of extracting the Green's function from the correlation of the microseisms that professor Zheng Sihua in the Institute of Earthquake Science China Earthquake Administration has given us, using the results of the sum of the correlation coefficient between the microseism on the vertical channel that recorded from two site, to estimate the velocities of the surface wave in Fujian, we found the velocities of the surface wave is between in 2.7-3.2Km/s,which is close to the observation.4. In order to make the attenuation of the microseisms clearly when the the storm occurred, we use the conclusion of Peter D. Bromirski to estimate the attenuation of the microseisms. Firstly, we suppose the dominant source of the microseisms is near the east of china sea, not in the open ocean where the highest waves occurred. Then base on this suppose to make sure the distance of microseisms transferred and to calculate the attenuation of the microseisms. It is proved that the microseisms attenuate as 1/r^1/2 and it is similar with the attenuation of the rayleigh waves.5. Based on the research of forefathers, we supposed that the nonlinear interaction of opposing wave components having nearly the same wave number results in a pressure excitation spectrum that propagates away from the sea surface at double the ocean wave frequency and couples into seismic waves at the ocean bottom, then we speculate connection between the ocean wave and the microseisms depending on the theory,. According to analysis, the ocean wave height determined from the microseisms recorded by the seismometer in Fuzhou was correspond with height of ocean wave recorded by buoys at Chongwu. It proves that the microseisms is mainly generated by the activity of the ocean wave.