GROUND MOTION SIMULATION CONSIDERING VELOCITY DISPERSION AND ITS IMPLICATIONS FOR SEISMIC HAZARD ASSESSMENT
Seismic hazard assessment is crucial for determining engineering fortification levels,guiding urban planning,mitigating earthquake disasters,and addressing secondary hazards such as landslides and mudslides triggered by earthquakes.Energy attenuation during seismic wave propagation is influenced by multi-angle scattering,physical dispersion,and geometric spreading.When conducting numerical simulations of post-earthquake ground motion,accounting for these factors significantly affects the accuracy of hazard assessments.This paper examines the physical dispersion characteristics of seismic waves in viscoelastic media.Through simulations of velocity dispersion and seismic wave time distribution in a simple one-dimensional model,we explore the impact of dispersion on the spatial distribution of seismic motion and its implications for seismic hazard assessment.A case study of the 2021 Yangbi MS6.4 earthquake further illustrates the importance of considering physical dispersion in seismic hazard analysis.In contrast to traditional ground motion prediction equations(GMPE),physics-based simulations of ground motion provide more reliable estimates of seismic hazard levels and enhance the accuracy of hazard assessments.It is well-established that,excluding site effects,peak ground motion parameters on bedrock decrease with increasing epicentral distance.However,considering the wave field dispersion characteristics reveals that peak ground motion parameters do not always decrease monotonically with distance;in some cases,they may even slightly increase.This highlights the complexity of seismic wave propagation through viscoelastic media.Further validation of these findings through refined,scenario-based numerical simulations is necessary.Additionally,with increasing epicentral distance,the amplitude of ground motion time histories decreases,while their duration increases.This low-frequency,long-duration seismic motion may be amplified under specific site conditions,such as in basins.The influence of the non-uniform viscoelastic medium results in varying attenuation rates for horizontal peak ground motion parameters at different angles.The findings of this study have important implications for national security,critical infrastructure,unconventional energy development,and secondary hazards such as landslides and mudslides.The integration of source physics,seismic wave theory,medium structure imaging,and structural stress analysis is essential for improving the accuracy and reliability of seismic hazard assessments.
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