Slip Distribution Of The Mw7.8 Nepal Earthquake From Invertions Of GPS Coseismic Displacement Observed Data

Earthquakes can cause surface deformation,which can invert seismic slip distribution and fracture models using surface deformation observation data.This thesis uses GPS co-seismic displacement observation data to accurately invert the slip distribution and the rupture of the Mw7.8 Nepal earthquake,and calculates the energy and magnitude of the earthquake.Also,the characteristics of inter-seismic atresia and strain accumulation release in the area are analyzed and the risk after earthquake is assessed with consideration of the rupture process at the surface and the damage caused by the earthquake.It is of great significance for understanding the motion characteristics of the plate in the South of Tibet.The co-seismic displacement observation data from 47 GPS stations in southern Tibet and 19 GPS stations in Nepal have been collected in this thesis to invert the slip distribution of the Mw7.8 Nepal earthquake.Using SDM inversion method and the Green's function based on the uniform half-space and layered earth model,the fault slip distribution of the earthquake is obtained.In addition,this paper discusses the effects of data distribution,fault geometry models,and different earth dislocation models on inversion of the slip distribution.The inversion results show that the maximum slip,the average slip,the fault dip angle,the strike and the seismic moment is 4.24m,0.84m,8°,284°and 5.61×10~200 Nm,respectively.More than 4 m of the slip is located within 20 km(with a depth of 9 to 12 km)from the epicenter.The earthquake is a typical low dip thrust type earthquake.The earthquake ruptures one-sided eastward from the initial rupture point,with an average depth of 10 km.Most of the ruptures are concentrated within a depth ranging from 8 to 20 km and there is almost no rupture when the depth is greater than 20 km.In the rupture,the main Himalayan thrust fault zone has a high degree of atresia in the shallow part,and the accumulated strain is not released completely.The post-earthquake deformation may have a greater impact on the southern part of China,which needs close attention in the future.Through the discussion of the inversion results,it is found that the location of the data distribution of the seismic influence on the distribution of the sliding,close to the epicenter of the data can be a very good inversion of seismic fault slip distribution characteristics.Without consideration of the influence of other parameters,the effects of the deviation of the fault dip angle on the fault slip distribution is great,,including the effects on the moment magnitude,maximum slip value,the correlation of data and model and the average slip value.When the deviation of dip angle is less than 10°,the difference of the maximum slip value can reach 30%;the average slip increases with the increase of the dip angle,and when the dip angle increases from 2°to 12°,the average slip increases by 25%.All the data used in the inversion are near field data,and the seismic source depth of this earthquake is about 10km,which belongs to shallow earthquake,so the stratiform structure has little influence on it.