The Study On Characteristics Of Offshore Ground Motion Records Based On K-NET Of Japan

The ocean is rich in water resources,biological resources,petroleum and mineral resources,and space resources.Countries around the world have begun to build marine projects to develop marine resources.China's territorial waters are located at the junction of many plates,and there are many major subduction zones and small subduction zones.These subduction zone earthquakes are prone to earthquakes.Therefore,in the construction of ocean engineering,the ground motions that may be encountered in ocean engineering must be considered.This paper studies the seismic development around earthquake resistance of ocean engineering.The main work is as follows:1.The research work of offshore ground motions at home and abroad is summarized,including the classification of source types,the research methods of offshore ground motions,and the current achievements of those methods.The problems existing in the study of offshore ground motions are also introduced.The ground motion records of the K-NET submarine station in Japan and the ground motion records of the relevant land stations were collected and compiled,and the ground motion records were grouped according to the source type,magnitude and epicentral distance,and the rationality of the grouping is demonstrated by the coefficient of variation.2.The characteristics of sea ground motion are analyzed from the perspective of amplitude,time duration and spectrum.Among them,PGA,PGV,PGD and other amplitude parameters are calculated.The 90% energy duration is calculated as the duration parameter.The energy parameters such as CAV and Arias Intensity are calculated.For spectrum,we calculate the normalized acceleration response spectrum,velocity response spectrum and the displacement response spectrum in the elastic phase while equal-intensity ductility spectrum are calculated for elasto-plastic phase.In addition,the uncertainty of the ground motion parameters and spectrum is analyzed by the coefficient of variation.3.From the perspective of the standardized elastic acceleration response spectrum and the equal-intensity ductility spectrum,the quantitative relationship between offshore ground motion and onshore ground motion is studied by calculating the spectral ratio of the offshore ground motion and the onshore ground motion.It is found that during elastic design,the difference between offshore and onshore groundmotion must be considered for the seismic design of medium and long period structures,especially the vertical component of offshore ground motion.When performing elastoplastic verification,when the magnitude or epicentral distance is small in the horizontal direction,it is necessary to distinguish the difference between the sea area and the land motion for the long-period structure.In the vertical direction,it is necessary to pay more attention to the difference of the impact of the offshore and onshore motion on the short-period structure.4.The three typical offshore ground motions including energy concentration,long-duration and long-period in the ground motion data are analyzed and some records are recommended.The amplitude parameters,energy parameters,elastic acceleration spectra and equal-intensity ductility spectra are sorted,and the ground motion recommendation is given in combination with European and American norms to provide reference for the ground motion input in the sea area.