| Seismic hazard analysis is one of the important components of earthquake loss prediction research.Seismic hazard analysis refers to the extent and characteristics of human construction projects and the possible earthquake impacts(ground vibration,fault rupture,and earthquake-induced secondary geological disasters)in the future.Up to now,the seismic risk analysis results may be significantly different from the actual occurrence of future large earthquakes.For example,the Tangshan earthquake in 1976 occurred in areas where seismic activity was considered to be relatively low,which indicates that the results of the current seismic hazard analysis still have great uncertainty.Seismic hazards at the site generally use ground motion(or seismic intensity)to exceed the probability of occurrence.The calculation method of ground motion surpassing probability has always been a hot research issue of concern.At present,the probabilistic earthquake risk analysis methods that are popular in the world provide the design basis for seismic fortification of buildings,structures,lifeline projects,and major engineering facilities.The method focuses on solving the probability value that the site may exceed the set ground motion value in the given time period in the future,or set the ground motion value under the danger level.Recent studies have mainly improved seismic activity models used in probabilistic earthquake risk analysis,such as ETIDE(epidemic-type aftershock sequence),temporally predictable models,seismic activity spatial distribution models,ground motion attenuation models,and probability calculation methods.However,in certain seismic hazard risk assessments,the use of the extremum ground motion density function(ie,the difference in ground motion surpassing probability)for earthquake risk is not suitable for replacing the ground motion occurrence probability,and there has been no treatment parameter uncertainty.The better way.Using a single index to describe the seismic hazard of the site can no longer meet the requirements of comprehensive earthquake reduction work such as seismic loss estimation and earthquake insurance,and rapid assessment of post-disaster losses.It is necessary to study how to accurately determine the occurrence probability of site ground motion.This paper combines the Monte Carlo method with the probability earthquake risk analysis method that considers the spatial and temporal inhomogeneity of earthquakes in China.The focus of this paper is on the 4 key aspects as follows:(1)Earthquake activity simulation of seismic statistics unit based on Monte Carlo random test methodSeismicity is one of the key research topics in earthquake risk analysis and seismic risk analysis.Seismic activity analysis is based on the strong spatial and temporal distribution of seismic events.It is generally represented by a seismic catalogue containing strong temporal and spatial information.Because of the limited length of time recorded by the instrument to record earthquakes and historical records of seismic events and the integrity issues,historical earthquake catalogues in the study area often fail to meet the needs of seismic activity research.Based on these limited data,methods and models established often It is impossible to accurately estimate the future seismic activity.Therefore,it is of great significance to simulate earthquake activity by simulating earthquake catalogs that satisfy the seismic activity characteristics of a certain space-time region.In order to characterize the spatial non-uniformity of seismic activity,seismic activity areas are generally divided into seismic statistics units and their internal potential source regions.This section focuses on the seismicity of seismic statistics units.Assuming that the seismic statistics unit meets the Poisson distribution model in time and the Gutenberg-Richter magnitude-frequency(G)relationship in intensity,a seismogram catalog simulation based on Monte Carlo random independent repeat test is established.method.Firstly,the conformity of the simulation catalogue was tested.Taking the Liupanshan-Qilianshan seismic belt as an example,the catalogue of earthquakes of m ?4 in each of 20,000 earthquake groups over the next 30 years,50 years,and 100 years was simulated.Analysis of the results analysis table shows that the probability density function of seismic distribution in each potential source area of the seismic catalog generated by the simulation is completely consistent with the spatial non-uniformity function of the earthquake.In combination with the Tanlu Seismic Belt,the use of the Tantalum Seismic Belt Catalog for earthquake prediction provides a good basis for future analysis of the probability of seismic hazards.(2)Simulation of non-uniform distribution of seismic activity in potential seismic regions based on Monte Carlo random test methodThe above seismic catalogue based on seismic statistical unit simulation only considers the time distribution of earthquakes,and does not consider the non-uniformity of spatial distribution of seismic activity.Probabilistic seismic hazard analysis method,the earthquake statistics unit within the further potential source area,the spatial heterogeneity of seismic function according to different magnitude of earthquake in potential focal region distribution inhomogeneity of the distribution of tertiary source area model.This article to our country commonly used seismic spatial heterogeneity distribution function as a different step earthquakes occurred in all the potential seismic source area of the probability density function,using monte carlo random experiment simulation method,the preceding has simulated earthquake seismic events within the statistical unit belonging to the potential seismic source area.Further on the basis of earthquake in potential focal region internal space evenly distributed hypothesis,using the monte carlo stochastic independent repeat test method,to determine the seismic events space coordinates(latitude and longitude).Since then by random simulation test,producing a set of meet the earthquake risk analysis in the statistical unit and its potential focal region seismicity spatial heterogeneity distribution assumption of a set of seismic events.Select Fen nutrient-laden seismic zone as the research area,in order to study the influence of the length of time different directories on the result,to generate the next 30 years,50 years,in 70,100 and 130,more than 20000 groups of 4 each directory.The results show that the probability density function of earthquake distribution in each potential seismic source area is exactly the same as the spatial nonuniformity function.Combined with the fen-wei seismic belt,the fen-wei seismic belt directory is used to predict earthquakes,providing a good basis for the subsequent probability seismic risk analysis.(3)the estimation of ground vibration at specified field pointsBased on the seismic catalog simulation,the ground vibration of the specified field point can be estimated according to the attenuation relation of ground vibration.Based on seismic elliptic attenuation model as an example,according to the simulation of the earthquake catalogue,converts the latitude and longitude coordinates to rectangular coordinates,and is the origin with the epicenter,latent source rupture direction of long axis direction,to determine sites in X,short for elliptic axle shaft for Y coordinates in rectangular coordinate system.Simultaneous elliptic equation and attenuation relationship,obtained by using dichotomy attenuation length of long axis and short axis of the ellipse,then long and short half shaft length),the epicenter distance and magnitude size into the sites of the ground motion attenuation relation can be obtained.Attenuation of uncertainty for processing,this article also USES the stochastic simulation test method,randomly generated accord with normal distribution N(0,sigma 2)random number(including the ground motion parameters such as peak ground motion,sigma 2 corresponding attenuation relationship of ground motion of logarithmic standard variance;In the case where the ground vibration parameter is seismic intensity,the standard variance of the seismic intensity attenuation relationship is imposed on the estimated ground vibration value,which is the estimated ground vibration value of the field point.(4)estimation of the probability and occurrence probability of field point ground vibration surpassingOn the basis of the field ground motion estimation based on the simulated earthquake catalogue,the probability and probability of the ground motion are estimated.First for each group of simulated earthquake catalogue of various seismic events,a maximum of determining ground motion caused by its sites(extreme),as a result of this group of random simulation test,through a large number of random independent group(usually 10000 or even 10 million)repeat the experiment,a series of maximum ground motion simulation to determine the sites.On the basis of this,the probability curve of exceeding the given ground vibration caused by the earthquake of the specified period of time is calculated as the result of seismic risk analysis.In this paper,on the basis of method study,baoji in shaanxi province as the research area,with seismic intensity of the ground motion parameter,the random simulation method is adopted to improve the seismic risk analysis,and to estimate the seismic intensity probability calculation results with the traditional method based on probabilistic seismic hazard analysis of China,comparing the calculation results found that the two basic consistent,but in the fine degree of flexibility,the model transformation method is better than traditional methods.In seismic risk analysis and earthquake damage prediction,using sites exceeding probability of earthquake ground motion for seismic risk factor,and seismic vulnerability is not consistent,need the further development of the probability of earthquake ground motion analysis method.Based on the estimation of the field point ground vibration value determined by the research content in(3)of this paper,the probability of different times of ground vibration with a certain intensity can be further obtained.Based primarily on groups of stochastic simulation calculate and determine the value of ground motion in earthquake directory,statistics to determine a ground motions occur the frequency,the number of different and divided by the number of sets of random simulation of the earthquake catalogue,get a ground motions occur the probability,the number of different shock and total probability.Based on the method study and taking baoji district as an example,the probability and occurrence number distribution of different earthquake intensities in the next 50 years are calculated.The results can provide a reference for earthquake damage assessment. |
PDF Full Text Request