Test Of PSHA Maps From Cost-benefit Analysis—Sichuan Case

China's seismic zoning plan is a national specification,and it is an important basis for the formulation of the countermeasures to prevent and mitigate earthquake disasters.Also,it is a basis for the government's policies and the seismic measures adopted by all kinds of engineering structures.The recently released third edition of the zoning map is based on the probabilistic seismic hazard analysis method and can be referred to as the PSHA zoning map.Taking Sichuan as an example of areas that are affected by major earthquake disasters,this paper evaluates the effectiveness of fortification and develops the method of assessment of PSHA zoning map by comparing the losses and casualties caused by the destruction of brick-concrete and steel-concrete structures in the actual earthquakes after the promulgations of the 1990 and 2001 zoning maps.Based on the statistical data released by the authoritative departments,this paper extracted and calculated the total number of houses built according to two PSHA zoning maps in different parts of Sichuan.With the help of PKPM and Guanglianda calculation software,the coefficient of increase in the civil construction cost of a typical brick-concrete and steel-concrete structure house designed according to different fortification intensity relative to similar houses without fortification was calculated.And the total investment in the seismic fortification of these two types of buildings in Sichuan are estimated to be 10.176 billion yuan and 12.743 billion yuan respectively.The estimation formula of direct economic losses and casualties was improved.With the help of the seismic vulnerability matrix related to the fortification intensity of brick-concrete and steel-concrete structures in Sichuan area,which was initially established by another postgraduate student,and the seismic vulnerability matrix of two types of unfortified buildings developed in this paper,the loss caused by the earthquake can be calculated.According to the 1990 version of the zoning map fortification,two types of building damage economic losses were 65.875 billion yuan less,with 16919 death and 32296 wounded less;according to the 2001 zoning plan,the economic losses caused by the two types of house destruction were 95.264 billion yuan less,with 17,645 fewer deaths and 34,272 fewer serious injuries.The implementation of the PSHA zoning plan has indeed had a good mitigation effect,avoiding more property damage and more serious casualties.The method based on fortification economic benefits and fortification security benefits is proposed to calculate fortification benefits,and the fortification benefits of the fortification inputs under the guidance of the 1990 and 2001 versions of the PSHA zoning maps with respect to Wenchuan earthquake are evaluated.For the severely affected area and affected area designated by the Wenchuan earthquake survey and assessment,their fortification benefits under the assuming higher and lower fortifications are calculated and analysed with comparison to fortification benefits of that according to the PSHA zoning maps The analysis indicates that the brick-concrete structure and brick-concrete structure fortification investment in Sichuan area guided by the PSHA zoning maps have certain fortification benefits,and increasing the fortification intensity once has better fortification benefits.The economic benefits and safety benefits of fortification in the heavy and light disaster areas with increase or decrease of the degree of fortification were calculated by using the same method.The results showed that the benefits were better in both the heavy and light disaster areas when the overall fortification intensity was increased by one degree and.Specifically,the province's economic benefit is expected to increase by 67.340 billion yuan,or 58.53 percent,with 6,591 fewer deaths and 31,524 fewer serious injuries.And the overall reduction of one degree of fortifying will bring less benefit.In particular,the economic benefit of the whole province will be reduced by 73.072 billion yuan,or 63.51%,with 28,838 more deaths and 36,523 more serious injuries.The results of this paper show that the fortification standards of China's PSHA zoning maps should be appropriately raised.