The Influence Of Site Features On Ground Motion Characteristic Parameters In Strong Earthquakes

Earthquake early warning (EEW) system using the principles that electromagnetic wave propagation speed is greater than the speed of seismic wave, and P wave velocity is greater than S wave, provides warning in advance for the area that the destructive S wave has not yet arrived, and allows people of each area to adopt effective mitigation measures in a few seconds or even dozens of seconds of warning time, and to reduce casualties and property loss as far as possible after the earthquake happened. First, we introduce the development and research status of earthquake early warning system, and put forward to the impact of site features which is mainly aimed at the shortage of the research in the theory of earthquake early warning.The contents of this paper are summarized as follows:(1) we use ANSYS software to simulate the seismic wave propagation soil with the reference to the method of ground motion parameter study in this paper, build the calculation model considering the local site conditions and propagation path, adopt the methods of seismic response(the instantaneous predominant period τpmax and predominant period τc) to calculate the surface ground motion parameters. And then result the influence of propagation path and local site conditions compared with the unfiltered seismic characteristic parameters. The results indicate that the method of τpmax or τc performs a good fitting precision, and the method of τc is better. From the study on Pd parameters of the initial P wave within the window of3s, we can find that it has good fitting relationships with PGA and PGV, and meets a certain precision.(2) We give a further study on the different amplification effects of soil types to the ground motion amplitude and seismic characteristic parameters with45kinds of homogeneous elastic single-layer models. This paper also show that when the soil type changes, characteristic parameters have better fits with peak ground acceleration in the whole process. We also compare the effects of soil thickness and multi-layer soil model.(3) We compare multi-layer soil model with the oblique incident angle of30°,60°and90°, and find that characteristic parameters have good linear relationships with peak ground acceleration which reacts ground motion intensity in the whole process.(4) This paper takes the Coalinga, El centro and Mammoth Lakes wave of oblique incidence as examples, to compare the changes of seismic wave characteristic parameters in the process of the incident angle changes from0°to90°. We detect that PGA,Pdmax and the value of τpmax rise gradually with the increase of incident angle, and locate at the highest point where the incident angle is80°, then down to the lowest point where the incident angle is90°. On the contrary, the value of τc gradually decreases to the lowest point at80°and then rise to the highest point at90°in general.