Analysis Study Of Affecting Factors And Modeling Of Casualties Of Earthquakes-based On Yushu Earthquake

BackgroundThe earthquake is one of the the human most threatening natural disasters, which isbursty, unpredictable and brings high causualties. China is a country where the seismicactivity has high frequency. Since the20th century, China accounted for35%of the globalearthquakes above7. From1949to1991, the number of deaths due to the earthquake in Chinaaccounted for54%of the total number of deaths caused by all kinds of natural disasters. Thetwo biggest earthquakes, Tangshan earthquake and Wenchuan earthquake respectivelyresulted in242thousand and69thousand deaths, with the number of people injured as manyas164thousand and374thousand. After an earthquake with mass casualties, the peakdemand of treatment of the wounded comes in the first24-48hours. Rescuing in the earlystage can prevent the deterioration of injuries and saves lots of lives. Therefore, a timely andeffective organization of medical rescue becomes critical.It is based on the availableinformation, analyzing the earthquake casualties influencing factors the variation pattern ofthe wounded occurrence to build a wounded occurrence model. The model can be used topredict the distribution of the number and type of the earthquake wounded, and give advice ofearthquake medical rescue to save lives. So the establishment of a rational and accurate modelwhich can predict the variation of causalties occurrence of earthquakes is always hotThe studies of factors affecting the earthquake casualties have occurred in foreigncountries since a long time. Earthquake focal depth, intensity, local geological conditions, etc.will affect the occurrence of the casualties, while the local population density, age structurealso have impacts on casualties. The studies of earthquake casualties influencing factors havegradual improvement and the casualties variating pattern draws constant attention. It’sbecoming more and more necessary to integrate them to prediuct earthquake casualtiesoccurrence precisely and give advises on the emergency rescue,saving lives. The purpose ofthis study is to analyze the influencing factors of earthquake casualties and the variationpattern of earthquake casualties were analyzed to summarize the strengths and weaknesses ofthe predictive models of earthquake casualties in the past.And after the Yushu earthquakewounded occurred empirical analysis, a mathematical modeling will be established in adynamic prediction model.Materials：Basic information of the previous large earthquakes at home and abroad,including <The earthquake case data of China> and the Internet information; using Medline, Pubmed, Proquest, ELSEVIER, Tsinghua Tongfang the CNKI Chongqing VIP database toretrieve the literatures of earthquake casualties influencing factors;Yushu earthquakeemergency medical files, reports and statistics of more than100copies from NationalMinistry of Health; having collected relief emergency medical rescue public documents ofmore than50copies of military activities in Wenchuan and Yushu earthquake, more than80copies of earthquake relief briefing from a Military Medical University,Methods:Including literature, expert interviews, field research method, systemanalysis,matrix math, Pareto distribution model simulation modeling. Applicating inductive analysis ofthe literature to summarize the factors affecting the occurrence of earthquake casualties, tosummarize existing prediction model of earthquake casualties; applicating field research,literature reviewing, statistical methods into the empirical analysis ofYushu earthquake’casualties; applicating matrix math, Pareto distribution into the modeling dynamic casualtiesprediction model; applicating matlab software earthquake into simulating and predicting.Results and Conclusions:1、 Further validating the seismic casualties`"two stages" patternOur team bring forward the seismic casualties dynamic variation "two stages" patternbased on Wenchuan earthquake, whose contents are:1、The casualties growth period isdivided into casualties fast growth period and casualties stable growth period by a inflectionpoint. After the fast growth of casualties at the early stage, a distinct inflection point comesout and it turns into a casualties stable growth period with a gradually decreasing growth ratetill the rescue work ends.2、The time of inflection point is related with the earthquakesituation,the rescue force covering speed and so on.With a different earthquake scale, thetime of the inflection point is different. Generally, after a earthquake with small casualties,theinflection comes more early, usually with in a week;After a earthquake with mass casualties,the inflection point comes more late, usually after a week,sometimes after two weeks. In thispaper, the growth trend analysis of the reported death of the earthquake verifies thecorrectness of the two stage pattern.The research proofed most seismic casualties agree with "two stage" pattern andverificated its correctness through logarithmic growth trend analyzing of domestic and foreignearthquakes report death`growth trends.2、Earthquake severity, buildings, population structure, post-earthquake relief and otherfactors affect the earthquake casualtiesThe earthquake casualties has many affecting factors, generally including the impact of the earthquake situation, the local environment, demographic factors, after the earthquakerelief behavior factors.The earthquake situation includes magnitude,intensity and time. Thecorrelation of seismic intensity and casualties is more credible than magnitude’s;Earthquaketime has relates with rate of staff in room and activities within a day. Local environmentalimpact includs the building structure and local geography. When Earthquake grade is fixed,the seismic performance of the building determines the extent of the damage of the building,directly affecting the casualties.The age structure,gender and education can also influence thecasualties.3、Existing predicting methods can only predict the number of immediate casualties, anddidn’t take the seismic casualties’"two stages" pattern into considerationThe earthquake prediction model of casualties basing on earthquake casualtiesinfluencing factors, can be basically divided into empirical formula, probability method,dynamic analysis, based on GIS method and emerging artificial neural network model pattern.These predictive models are considered lack of rescue behavior after the earthquake rescuethe life of the earthquake victims in the outcome, which cause the models can not meet theseismic casualties Variation Pattern.4、The Yushu earthquake casualty is influenced by sesmic severity, relief speed and otherfactors, while its growth trend is in line with “two stage” pattern.Yushu earthquake casualty growth trend is in line with the earthquake casualties "twostage " pattern.The sixth day after the earthquake, which is the reflection point, divided thewhole growth into two stages:the fast growth stage before the point and the stable growthstage after it.Seismic intensity, time of occurrence, the local architectural structure and earthquakedamage situation,after the earthquake relief behavior and other factors have impacts on timeand space distribution of casualties ofYushu earthquake. Yushu local geologicalcharacteristics determine the spatial characteristics of casualties,which mainly shows "SouthNorth small casualties, light west of East mass casualties" distribution,consistent with theseismic intensity map. Local construction are more of earth and wood so that buildings arevulnerable to collapse, causing casualties after the earthquake.5、The overall trends of casualties、the total numbers of rescue staff and the woundedevacuated by air ofYushu earthquake showed similar variation pattern.The overall trends of casualties、the total numbers of rescue staff and the woundedevacuated by air ofYushu earthquake showed similar variation pattern.: a period of rapid growth and the stationary phase. The total number grow rapidly in the early stage, andmaintain steady growth to saturation after take on the inflection point within a week after theearthquake. This indicates that the earthquake, the local environment, population structuredetermines the initial state of casualties of personnel after the earthquake, but the disasterrelief personnel rescue work and evacuation of the wounded casualties determine thefollow-up changes.6、The simulation of the model is in keeping with the actual occurrence of casualties andvalidated the “two stage” pattern.The numbers of the wounded, the deaths, the severe injuries of the model simulation cankeep with the actual occurrence of the Yushu earthquake in the same magnitude.Injured erroris42.52%,and deaths error of41.04%, severe injuries error23.01%. The trends of thewounded treated daily increase simulated by the model in in line with the "two stages" pattern.After the early rapid growth, the wounded growth inflection point turns on the sixth day andthe growth enters into the sustained period. In the different sesmic intensity, as an earthquakeis smaller, the inflection point occurs sooner, and an earthquake is larger, the inflection pointcomes later, which agree with the sesmic scale’s impact on the inflection point in the “twostage”pattern.7、The model predicts whether the rescue relief arrive in the first three days is crucial toreducing casualties.The simulation results show that it is significant that the rescue relief staff all arrive inthe first three days: All rescue personnel arriving in the first three days brings the total numberof casualties down to52%of the actual number, which is better than the situation in theactual rescue speed.The strengthening of medical staff in stricken regions, reinforcing reliefall arriving in the first three days can lighten the casualty, the severity of wounded andimprove the prognosises.