Analysis Of Ground Motion Attenuation Characteristics

In recent years, the statistical analysis of attenuation relationship of longperiod ground motion and the study on the influencing factors of seismicattenuation characteristics are the major research subjects in earthquakeengineering. Based on the records from2earthquakes occurred in theChristchurch region and26destructive earthquakes occurred in Sichuan-Yunnanregion, the key problems in the characteristics analysis of ground motionattenuation, the attenuation relationship establishment of long period groundmotion and effect of hypocenter depth on the ground motion attenuationcharacteristics, are deeply analyzed. The main contents are as following:1. The research status for the attenuation relationship of long period groundmotion and the relevant research results are generally introduced. According tothe recent study, some problems still remain unsolved. The reason why it’snecessary to carry on this research is explained.2. Based on the records from2earthquakes occurred in the Christchurchregion, by using the acceleration baseline correction method, the calculationmethod of peak ground acceleration, the acceleration response spectra and thecumulative absolute velocity and the2steps regressing least square method, thecorresponding calculation and regression analysis is done to analyze the peakground acceleration, the acceleration response spectra and the cumulativeabsolute velocity. The distribution of ratio of vertical to horizontal ground motionacceleration is got. The attenuation relationships of the peak ground acceleration,acceleration response spectra at4period points and cumulative absolute velocityare established. The effect of hypocenter depth on the peak ground accelerationratio and attenuation characteristics of ground motion parameters is discussed.The acceleration respongse spectra at6typical sites of Christchurch region arecompared to further study the effect of the hypocenter depth on the accelerationresponse spectra. According to the different characteristics of ground motion, theearthquake damage difference in2earthquakes is analyzed.3. The artificial ground motion generation method and one-dimensionequivalent linear method of seismic responses for soil layers are introduced. Theground motion response of6calculation models with different site conditionsunder the input of artificial ground motion is calculated. The response spectra onthe free surface and bedrock are compared to discuss the effect of soil layerthickness on the long period ground motion. By compared with the strong motionrecords on different site condition from Wen Chuan earthquake, the numericalsimulation results are verified.4. Based on the numerical simulation of the typical sites and the analysis ofaccelerogram from Wenchuan earthquake, the applying conditions of which thestrong motion accelerograms on the soil layer sites are used directly to theStatistical regression analysis of the attenuation relationship of long period acceleration response spectra on the bedrock site, are discussed.5. Based on the strong motion acceleration records meeting the screeningconditions, the2steps regressing least square method is used to establish theattenuation relationship of acceleration response spectra at6periods from8to15second. By comparing the change of attenuation relationship with the magnitudeand distance and the actual earthquake records, the regression statistic rationalityof attenuation relationship is discussed.6. The study work in this paper is summarized, and the following work to bestudied further is put forward.