Study On Ground Motion Attenuation Relationship For The Northeastern Margin Of Qinghai-tibet Plateau Based On NGA Model

The northeast margin of Qinghai Tibet Plateau is the area with the strongest tectonic deformation in the late Cenozoic zone.Active faults are densely distributed and destructive earthquakes occur frequently.There are five earthquakes with a magnitude of more than 8 in the historical records.Frequent strong earthquakes have caused huge losses to people's property and life safety in the disaster area.After a major earthquake,based on the ground motion attenuation relationship,the ground motion distribution in the earthquake area can be predicted in time,which can play a key role in evaluating the earthquake damage loss,responding to command and decisionmaking and judging the hardest hit areas,and help departments at all levels improve the pertinence of emergency rescue and reasonably allocate rescue capacity.Therefore,the establishment of ground motion attenuation model suitable for the northeast edge of Qinghai Tibet Plateau Based on strong motion data is of great significance for earthquake prevention and disaster reduction in this region.In this paper,the records of strong motion and the site data of relevant stations are collected by China strong motion network.Taking NGA-West2 ground motion attenuation relation model as a reference,the basic form of the attenuation model in this paper is determined on the basis of comprehensively considering the seismic geological structure and strong earthquake data in this area.A ground motion attenuation model considering fault distance,fault type,hanging wall effect and site conditions is established by using the random effect regression method,and applied to the earthquake impact field assessment.The main contents and conclusions of this study are as follows:(1)Based on the four earthquakes of Hutubi Mw6.0,Jiuzhaigou Mw6.5,Lushan Mw6.7 and Wenchuan Mw7.9,the applicability of the NGA model in my country is discussed and compared with the CH15 model in my country.The research shows that the prediction effect of the CH15 model is better than that of the NGA model when the magnitude is smaller.With the increase of the magnitude of the earthquake,the prediction residual of the CH15 model is significantly larger than that of the NGA model.(2)A set of ground motion attenuation models for the northeastern margin of the Qinghai-Tibet Plateau is obtained,which considers the near-field saturation effect,nearfault effect,site conditions,hanging wall effect and fault type.The model is verified by the strong earthquake records of Wenchuan Mw7.9 earthquake,Jiuzhaigou Mw6.5earthquake and Minzhang Mw6.0 earthquake.The results show that the prediction results of the earthquake motion in the northeastern margin of the Qinghai-Tibet Plateau are in good agreement with the actual results.The residual analysis results show that the prediction residual of the model in this paper is generally smaller than that of the Zhang13 model and the two NGA models,and the prediction results are relatively better.(3)The generation system of ground motion impact field is developed and applied to the assessment of the impact field of the Maduo Mw7.3 earthquake in 2021 and the Menyuan Mw6.6 earthquake in 2022.The theoretical results predicted by the model in this paper are more consistent with the actual situation.The research results of this paper have significantly improved the prediction accuracy and efficiency of the large earthquake Shakemap and earthquake impact field.