Estimation Of Near-fault Long-period Strong Ground Motion Based On Kinematics Rupture Process

Long-period ground motions near faults cause damage to engineering structures and a large number of casualties in the near-fault area.With the rapid development of China’s economy,large-scale buildings such as high-rise buildings and large-span bridges have emerged in various cities.Near-fault long-period ground motions with pulse characteristics,characterized by high amplitude,long period,and energy concentration,can cause more severe damage to long-period structures.In probabilistic seismic hazard assessment,it is necessary to consider the distribution of such ground motions within the region.Ground motion simulation reproduces the occurrence and propagation process of ground motion by establishing the mathematical model of the source and the seismic wave propagation medium.Considering the uncertainty of seismic source parameters,setting scenario earthquakes on active faults can assess the risk of large earthquakes occurring in the future,and has important engineering value for disaster prevention and reduction in the region.The work of this article mainly includes the following four aspects:(1)conducting near-fault long-period ground motion simulation for historical earthquakes;(2)Considering the probability distribution of velocity pulses in the near-fault area;(3)Evaluation of near-fault long-period ground motion based on scenario earthquakes;(4)Synthesize broadband seismic motion based on the results of long-term seismic motion evaluation near faults.The innovation points of this article include:(1)Providing a long-period strong ground motion estimation scheme for historical and future earthquake events with multiple source rupture modes and upper magnitude limits;(2)Based on the simulation of long period strong ground motions in source physics,study the velocity pulse distribution in the near-fault area,fit it with existing pulse distribution models,and provide statistical characteristics of pulse parameters.The main research content is as follows:Chapter Ⅰ and Ⅱ introduce the research background,significance,methods,and route.Chapter Ⅰ mainly introduces the characteristics and classification of long-period ground motion,summarizes the concepts of near-fault pulse-type ground motion and probability distribution,summarizes the current research status of long-period ground motion simulation and ground motion evaluation,analyzes the shortcomings of current research results,and explains the significance and purpose of various studies in this article.Chapter Ⅱ mainly introduces the development history of the finite difference method and the basic principles and steps of the ground motion simulation software GMS based on the finite difference method.The steps,source parameters,and crustal media of the finite difference method for simulating near-fault long-period ground motions are summarized,and the main ideas of the ground motion evaluation scheme are summarized.Chapter Ⅲ and Ⅳ take two earthquakes with observation recoDRS as research cases.In chapter Ⅲ,the finite difference method is used to simulate the long-period ground motion of the Lushan Mw6.6 earthquake in 2013,and the waveform,velocity spectrum,and displacement spectrum of the simulation results and observation results are compared.Discuss the effects of a one-dimensional crustal model on the amplitude of long-period ground motions in the absence of a precise three-dimensional crustal structure.Finally,sensitivity analysis was conducted by selecting stress drop,rise time,and rupture propagation time,laying the foundation for conducting seismic motion evaluation.Chapter Ⅳ introduces the theory and development of probability models for velocity pulse distribution.On this basis,the 3D finite difference method is used to simulate the long-period ground motion of the 2016 Kumamoto Mw7.1 earthquake.Combining the probability model of pulse distribution,discuss the distribution characteristics of near-fault velocity pulses and evaluate the statistical correlation between pulse parameters.Chapters Ⅴ and Ⅵ conduct research on the multi-source rupture modes and upper magnitude limits of historical and future earthquake events.In chapter Ⅴ,the finite difference method is used to evaluate the near fault long-period ground motion of Qujiang fault,and the uncertainty of source parameters is considered respectively to evaluate the fault process and possible damage caused by possible earthquakes on the fault zone.Chapter Ⅵ applies the results of long-term seismic motion evaluation near faults.Long period ground motion simulation of the Anqiu Juxian fault under three magnitudes of Mw7.0,Mw6.5,and Mw6.0.In addition,the mixed method of empirical Green function method and finite difference method is used to simulate the broadband ground motion of Ms7.2 earthquake on Huya fault in Songpan Pingwu area.By analyzing the attenuation relationship of seismic motion,select the seismic motion that meets the requirements for scenario earthquakes.Chapter Ⅶ summarizes the main content of the entire article and looks forward to the results of applying near-fault long-term seismic motion assessment in the future.