Mechanism Model Of Infrasound Abnormality Before Strong Earthquakes

Infrasound abnormality often was observed just several days before strong earthquakes occurred around the world, so infrasound abnormality could be an important earthquake precursor. It is significant to the imminent prediction through researching infrasound abnormality and accrued mechanism.The infrasound appeared in the days before earthquake is not only very important to the imminent prediction but also associated with geological actions at the last stage of earthquake incubation. The scholars of domestic and overseas brought forward some representative mechanism models, but the model explorations do not refer to the befall of infrasound at present. In this paper a 2-D model in which a layered rock geo-structure, air media and their interaction were included was proposed to simulate the formation of infrasound by the transient dynamic finite element method. The waveform and frequency of the infrasound simulated were analyzed. The results showed that the proposed model could produce infrasound which frequency agrees well with the observed and it might be a true mechanism of infrasound abnormality formation. The frequency of the infrasound was over the expanse-contracting period of the earthquake source body. The fluctuating range of the air pressure during the contracting was greater than that during the expanse.A mechanism model of infrasound producing in earthquake incubating was proposed in which interaction between atmosphere and deformation of Earth surface caused by dynamic behavior of geologic bodies in final stage of earthquake incubation causes the observable infrasound. As an example to verify the model geological behavior in the Northeast Japan area was modeled numerically and analyzed by two dimensional finite element methods (FEM). A layer geological model and effect of the Pacific subducting plate were included in the numerical model. Based on the dynamic coupling theory between structures and fluids, infrasound was obtained by numerical simulations. Good agreement between the observed and the simulated suggests that the proposed model is reasonable.