Effects Of Steep Slope Topography On Ground Motion

Earthquake damage survey shows that local irregular terrain is an important factor affecting the response of ground motion.Among them,the disasters caused by steep slopes,cliffs,mountains and basins have caused widespread concern.At home and abroad,a large number of studies have been carried out on the influence of local topography using numerical simulation methods,and fruitful results have been achieved.In this paper,the steep slope and complex terrain are selected.The numerical simulation method is used to study the influence of two terrains on ground motion.The research contents are as follows:1.Numerical simulation of the ground motion response of steep slopes under vertical incidence of SV waves by concentrated mass finite element method,using existing research results to test the reliability of numerical simulation.2.The numerical simulation of concentrated slope finite element method is used to analyze the influence of slope of steep slope,thickness of upper soil and incident angle on ground motion under the incident of SV wave.The results show that: 1-3 Hz is the seismic response amplitude frequency band.The steep slope has a large amplification effect on the ground horizontal ground motion on the steep slope.The slope apex amplification effect is the most obvious,and the ground horizontal ground motion under the steep slope has a weakening effect.The point weakening effect is most obvious.The smaller the slope of the steep slope,the weaker the response of the ground motion;the thicker the upper soil,the greater the ground motion amplification on the steep slope,the weaker the barrier function under the steep slope,and the ground motion barrier functioning away from the corner under the steep slope becomes a magnifying effect.And as the thickness becomes larger,the amplification effect is enhanced;the increase of the incident angle enhances the amplification effect of the ground motion above the steep slope and the barrier action of the ground motion under the steep slope,and the obvious oscillation occurs in the horizontal and vertical directions of the high frequency band,and the vertical direction Show a certain periodicity.3.Establish the 3D real terrain digital model of Lushan area,select the actual aftershocks and the parameters of the source inversion results as the analog input source,and analyze the amplification effect of the complex terrain near the station in the low frequency range.Prior to this,this paper compares the station position simulation record with the actual station observation record to verify the reliability of the numerical simulation.The analysis shows that the PGV distribution in the calculation area is complex in the 3Hz frequency band and has a certain correlation with the terrain variation distribution.The PGV of the mountain top is obviously larger than the value of the mountain foot.The PGV distribution in the calculation area of the 1Hz frequency band is relatively simple,and there is basically no influence of terrain.The difference in PGV distribution is more caused by the influence of the source parameters.The ground motion of the mountain section near the BXD station is analyzed.The amplification of the ground motion of the mountain is more obvious in the horizontal direction.The magnification of the mountain top is the largest,about 6.0(EW)and 4.0(NS).The amplification effect of the UD direction on the ground motion at the foot of the mountain is more obvious,and the magnification is about 6.0.