Ground Motion Prediction Equation For Subduction Earthquakes

In recent years,with the continuous development of coastal cities in China,increasing attention has been paid to the research on offshore seismic engineering.In coastal areas,subduction zones formed by the compression of tectonic plates have attracted researchers' attention due to their complex geological structure and frequent seismic activity.The seismic study of subduction zone needs fully understanding of the geological structure in subduction zone.In order to study the characteristics of ground motion for subduction zone,a wide and effective ground motion database is needed.The main contents and results of this thesis are as follows: earthquake discrimination and classification of subduction zone,establishment of ground motion database of subduction zone and ground motion attenuation relationship.The main research contents and results are as follows:In this thesis,the seismic identification and classification methods based on the geological structure,source location and source conditions of subduction area are summarized.By using the mixed method of two kinds of focal fault mechanism solution and 3-D geological structure model of subduction zone,298 subduction zone earthquakes are classified into four types: interface earthquake,intraslab earthquake,outer-rise earthquake and crustal earthquake by using the mixed method of two kinds of focal fault mechanism solution and 3-D geological structure model of subduction zone.Research shows the seismic classification results are affected by the selected seismic data sources,and different seismic classification methods will lead to the difference of results to a certain extent.At the same time,the classification method based on the mixed source fault mechanism solution method and the 3-D geological structure model used in this thesis can make the subduction earthquakes that may not be classified due to insufficient seismic information get classified,and it will not cause obvious deviation compared with the original classification results.By using the filter corner cut-off frequency selection algorithm and NGA standard ground motion processing flow,the subduction zone ground motion data collected are uniformly filtered,then ground motion intensity values based on Rot D50 median value were calculated,including PGA,PGV and 5% damping ratio PSA at 0.01 s to 10 s at 105 periods.After using three methods to collect site condition information and calculating two kinds of source distance,a gound motion database of subduction zone contains 290 subduction zone earthquakes,2588 seismic stations in six areas and 34990 ground motion records is established.It may provide data support for seismic research and practical engineering in subduction zone in the future.Research shows that the filter corner cut-off frequency selection algorithm can realize the efficient processing of ground motion records and avoid the subjectivity brought by the manual selection of corner cut-off frequency.After selecting ground motion records,a ground motion attenuation model was established in the subduction zone with the applicable range of moment magnitude 5.0 to 9.0,the maximum source distance between 300 km and 500 km,and the seismic depth less than 200 km.Through the residual analysis,original model parameters from crustal earthquake ground motionwere modified to conform to the ground motion attenuation characteristics for subduction zone.Finally,the model in this thesis is compared with four ground motion attenuation models for subduction zones,and the validity and applicability of the model are verified,which will provide theoretical support for future seismic research in subduction zones and actual disaster prevention engineering calculation.