Research On Lethal Assessment Technique Of Earthquake Death Based On Field Investigation

Earthquakes are one of the most important natural disasters that threaten the safety of human life and property and cause losses due to their suddenness,unpredictability and the magnitude of the damage caused.Earthquakes in China have the characteristics of high frequency,high intensity,shallow focus,and wide distribution,resulting more casualties and property losses.The study of earthquake death assessment methods plays an important role in earthquake emergency rescue and is also an important part of earthquake disaster risk assessment.The current assessment methods for earthquake deaths are mainly divided into two types: methods based on building vulnerability and methods based on ground motion parameters.Among them,the assessment method based on the vulnerability of the building requires strict and accurate building basic data,which results in certain restrictions on the assessment results.The methods based on ground motion parameters are mostly based on a certain amount or within a range of earthquake data to build models,resulting in obvious regional limitations of the model method.The purpose of this study is to propose a concept of the lethal level through a large number of field investigations and historical earthquake data.To construct a matrix based on the lethal level grade and the mortality rate of each intensity,construct a model method for the evaluation of deaths based on the lethal level,and the method of lethal level of field investigation.It can provide theoretical and technical support for pre-assessment,risk assessment before earthquake and rapid assessment after the earthquake.The main progress includes the following aspects:(1)Put forward the concept of lethal level.The so-called lethal level is the comprehensive possibility or level of various factors that may cause the death of people after an earthquake in a certain area.The best indicator to describe lethal is the mortality rate caused by the earthquake.The results of various death factors caused by each earthquake are comprehensively reflected in the mortality rate of the disaster area,especially the mortality rate by intensity.The lethal level is from high to low,corresponding to the possibility of death after building damage from large to small,the possibility of death from secondary disasters from large to small,and the traffic conditions of disaster relief from poor to good.(2)Construct a lethal level matrix.Based on the grouping characteristics of the fitting results of the intensity-mortality rate data in historical earthquakes,the grouping phenomenon of historical earthquake cases was discovered,based on the results of a large number of field investigation experiences,and the identification of iconic earthquake cases,it is found that the grouping of historical earthquakes is not based on the location of the spatial distribution,but the intensity-mortality rate and the lethal level reflected by each group of earthquakes.According to the grouping characteristics of historical earthquake cases,and based on the ± 50% error requirement of the grouping,the lethal level is divided into 11 levels of A-K,and the interval range of each lethal level is defined.Combining the actual mortality rate data of historical earthquakes in the earthquake group,and taking the iconic earthquake as a constraint,the mortality rate of each intensity of the earthquake is divided into 11 separate intervals,each case group corresponds to a lethal level,and also corresponds to a group with mortality rates of intensity.Based on this correspondence,a matrix based on the lethal level and the mortality rate by intensity was constructed,and the country can be divided into 11 grade intervals,and each grade corresponds to a set of VI-XI degree of dominance mortality rate data.(3)Construct a death evaluation model based on the lethal level matrix.Since the matrix is based on the grade of lethal level and the mortality rate of each intensity,in the case of determining the regional lethal level,it is possible to quickly assess the number of deaths based on the number of populations of each intensity under this level and time adjustment coefficient,the validity and practicability of the evaluation model proposed in this paper are verified from the perspectives of historical earthquake cases and practical applications.(4)Carried out the method research on the lethal level in the field investigation.Through the calculation of historical seismic data,combined with a large amount of field investigation experience,the range of lethal levels of each building type was determined,and based on the value of this interval,according to the types and weight ratios of different building types and other influencing factors,a method for calculating the lethal level in field investigations was constructed.(5)Combining with the content of earthquake disaster loss pre-assessment work,the application research of the relevant models proposed in this paper in actual investigation work such as pre-assessment is discussed.The calculation models of the lethal levels of different administrative levels in the field investigation are constructed,which can provide theoretical support for the field investigation working methods.The main conclusions of this study include the following aspects:(1)Through the study on the mortality rate of historical earthquake cases,it is found that the mortality of adjacent intensity generally differs by 3-16 times,the average value is about 10 times,and there is an exponential relationship.Through the fitting analysis of the mortality rate of each intensity,the grouping characteristics of historical earthquakes are found.The earthquake cases located in different areas may be in the same group,that is,some distant earthquakes sometimes show similar mortality rates;the change rate of mortality rates of different earthquake cases in the same group is less than 50%.However,earthquake cases in adjacent areas may be located in different groups,that is,the mortality rate of earthquake intensity in some adjacent areas may sometimes be significantly different.The mortality of historical earthquake cases cannot be quoted at will.(2)Through data analysis,combined with field investigation experience,it is found that the grouping characteristics represent the separation interval of mortality rate and indicate the difference in the lethal level of the regions.The mortality rates of different earthquake cases located in the same province may vary greatly,indicating that even regions in the same province may have different lethal level.However,earthquake cases in different provinces that are far apart may have approximately the same mortality rate,indicating that some non-adjacent different areas may also have approximately the same lethal level.The grouping of historical earthquakes is not based on the location of spatial distribution,but is related to the lethal level and the mortality rate.Based on the grouping characteristics,the lethal level is divided into 11 levels,and each level corresponds to a group of intensity mortality rate intervals.Combined with the real data of historical earthquake cases,a matrix based on the lethal level and the mortality rate by intensity was constructed.The higher of the lethal level,the higher of the corresponding intensity mortality rate.The lethal level and the mortality rate show a positive correlation.(3)Based on the building damage proportion data in the historical earthquake case data,a lethal level calculation model was constructed.Based on the data of building types and proportions,combined with field investigation experience,the range of lethal levels of various types of buildings was obtained.Among them,the lethal level range of adobe structure is between 0.85-1,the civil structure is between 0.7-0.95,the brick-wood structure is between 0.6-0.9,the stone-wood structure is between 0.55-0.9,the brick-concrete structure is between 0.25-0.7,the wooden structure is between 0.2-0.4,the frame structure is between 0.1-0.3,the steel structure is between 0.05-0.15,The lethal level range of different types of buildings is a non-equal partition,and there are overlapping areas between each other.(4)Based on the range of lethal levels of different types of buildings,through the determination and weight calculation of the influencing factors of each type of buildings,as well as the regional influencing factors,construct the lethal level calculation model in the field investigation.Combined with the experience of field investigation,the calculation model of lethal level of different administrative levels was constructed.Combined with the results of the pre-assessment field surveys conducted in Yancheng City and Suqian City of Jiangsu Province,the scientific and expandability of the evaluation model proposed in this paper is verified.(5)Based on the lethal level matrix,a human death assessment model was constructed.Under the premise of determining the regional lethal level,a quick assessment and calculation was performed based on the mortality rate and the number of people in each intensity corresponding to the level.Through the verification of 8 historical earthquakes and the actual application verification of 22 actual earthquakes since 2018,it is found that the error between the model evaluation results and the actual number of deaths is within ±30%,indicating the effectiveness and practicability of the death assessment model based on the lethal level.