using the h/v spectral ratio forestimating the vulnerabilityindex of a urban area

the subsurface topography and the dynamic specification of soils have important effect on the ground motion response. during the age of cities, the building have constructed by the different techniques, materials, styles and standard codes. the researches have shown that the buildings have different response to earthquake related of their materials and design rules. the soil layer specifications are recognizing by different geotechnical and geophysical methods, including geotechnical and geophysical as well as spectral ratio. horizontal-to-vertical spectral ratio (h/v) of microtremore was introduced by nakamura (1989). this method is very usable in site characterization studies due to its low budget and easy use. in this paper, it has presented a method for estimating the degree of vulnerability of structures using spectral ratio h/v. in a vulnerability study in the city of shiraz, the predominant frequencies are derived for the different parts of the city. these data have used to define a coefficient of vulnerability for the earth. for this purpose, 11 different building such masonry, steel or concrete structures were selected. the main frequency and amplification of microtremor h/v spectral ratio for building has been obtained. furthermore, the resonant frequency and amplification factor of the ground have been calculated. the vulnerability index of soil kg and vulnerability of building kb were defined. comparison of these coefficients it was recognized a damage factor η of building during the earthquake. this parameter leads to a fast and inexpensive method for preparing a disaster program for an urban area. in this paper, the damage rate of different building at shiraz city was obtained. in addition, the damage potential of all the city area was calculated.