Coherence Variation Of Ground Motion With Depths

Earthquake ground motion is a complex temporal and spatial process, the ground motion differs in location in one earthquake, due to the effects of wave passage, incoherence, site response and attenuation. The spatial coherency relationship of ground motion is becoming a key concern of earthquake engineering and seismic design research-for the reason that it is a basis for the study of spatial variability of ground motion and also plays a significant role in seismic hazard analysis, loss assessment, disaster relief and reconstruction, etc.The ground motion coherence analysis with variation of depths of soil layer is performed using three array’s strong motion recordings including six earthquakes of Treasure Island array, fourteen earthquakes of La-Cienega array and three earthquakes of Eureka Samoa array in California Strong Motion Instrumentation Program. The regularity the ground motion coherence with change of depth, site condition, and earthquake epicenter distance is studied through this process. A reasonable experience coherence model is presented. The details of this dissertation are as follows:Part Ⅰ:The ground motion coherence of both the ground surface with different depth of soil layer and the deepest point of soil layer with different points above are calculated at Tre(?)ure Island array, La-Cienega array and Eureka Samoa array, using average periodogram algorithm based on303seismic recordings in23earthquake of three CSMIP arrays.Part Ⅱ:Considering the influence of site condition, epicenter and transmission route, the ground motion coherence with change of depth of soil layer, earthquake epicenter distance, frequency and distance of area points is studied using the random statistical method.Part Ⅲ:After arrangement the regression information of three arrays, the coherency function of three arrays is obtained at the depth of Om to-10m,0m to-30m,0m to-100m,-100m to-90m,100m to-70m and-100m to0m with different earthquake epicenter distance of10km,30km,60km and100km to illustrate coherency the variation law of correlation of ground motion in different spatial points.