| In contrast to the artificial ground motion synthesis method based on the decay of ground motion parameters and the broadband ground motion simulation method,the deterministic ground motion simulation method based on the numerical simulation of seismic fluctuations is gradually being used to simulate and predict the ground motion field required for the construction of seismic scenarios and earthquake hazard assessment.The main reason for this is its relatively well established seismological theoretical background;it considers not only the effects of the source,path and field on ground motion but also the effects of the coupling between the three on ground motion.In recent years,deterministic simulation methods based on the Legendre spectral element ground motion numerical simulation method have been widely used in global-scale ground motion simulations,regional topographic effects,and basin effects analysis.Although this method can theoretically consider arbitrary forms of kinematic finite-fault source models,relatively little work has been done to discuss the implementation of source models in detail in this method.The thesis work is centred on the implementation of mainstream kinematic finite-fault source models in the Legendre spectral element deterministic ground-motion simulation method,and the preliminary conclusions of the main research work are as follows.1.two types of mainstream kinematic finite-fault source models are presented: the Grave & Pitarka random source model and the Irikura asperity source model.The global and local parameters(deterministic and stochastic)involved in the generation of the two types of models are described in detail.The spatial distribution of fault slip,rise time and rupture time for the two types of models are given for different moment magnitude scenarios.Based on this,a hybrid source model generation technique combining both the Grave & Pitarka random source model and the Irikura asperity source model is presented,and kinematic finite fault sources are generated for different moment magnitudes using this technique.2.Based on the idea of combining small earthquakes with large ones,the finite fault sources are split into subfaults that can be characterised by moment tensor sources.The three types of kinematic finite-fault source models are implemented in SPECFEM3 D by combining the sub-source input interface provided in SPECFEM3 D,a deterministic ground-motion simulation software based on the Legendre spectral element ground-motion numerical simulation method.On this basis,the influence of the subfault size and the selection of the Legendre spectral cell grid size on the simulation results is discussed.The results show that,for fourth-order cells,the choice of subfault size has a small effect on the simulation results of ground motion in the highest frequency band reachable by the numerical simulation,provided that the subfault size is less than or equal to the cell grid size.3.The influence of the selection of the source model on the ground vibration simulation results is discussed for two types of subsurface structures:(1)homogenous infinite medium(2)layered medium(California region and Sichuan-Yunnan region),with reference to the prediction equations of the ground vibration parameters for the California region in 2014.The results show that:(1)the PGV and PSA amplitudes at 2s,3s and 6s for ground motion predicted by the three models are comparable,but near the fault distance of 20 km,there is a steep drop in ground motion parameter amplitudes based on the asperity dislocation model,and the amplitude magnitudes are lower than those of the other two models;(2)using the Grave & Pitarka random source model and the California laminated medium,the simulated ground motion parameter amplitudes are comparable to those of the predicted ground motion parameters.(2)the simulated ground motion parameter amplitudes are comparable to those predicted by the ground motion parameter prediction equations using the Grave & Pitarka random dislocation model and the California layered medium;(3)the regional layered medium structure has some influence on the ground motion parameter simulation results,but it is not obvious in California and Sichuan-Yunnan,where the crustal amplification effect is about 2times. |
