A method of seismic microzoning based on the vulnerability coefficient

Abstract

The research objective is to develop a new method of seismic microzoning (SMZ) based on the spectral ratios between seismic signal’s horizontal and vertical components, i.e. on the vulnerability coefficient of the topmost soil stratum. Methods of research. The HVSR spectral ratio analysis has been used for a long time in various modifications. However, in author’s opinion, what’s new is the approach to seismic hazard zoning proposed in this research. It uses the vulnerability indices and subsequent recalculation into seismic intensity increments. The SMZ method based on the vulnerability coefficient considered in this article is not mandatory, although it is a variation of the spectral ratio method. It may be regarded as an addition to the mandatory seismic stiffness method. The combination of these SMZ methods will arguably increase the capabilities of the method as a whole and improve the accuracy and adequacy of a schematic map of seismic intensity increments. One of the advantages of both spectral ratio method and SMZ method based on the vulnerability index, is that they allow to take into account inelastic and nonlinear deformation processes when strong wave movements impacts on soils. Research results. Based on the calculated spectral characteristics of soils, the method makes it possible to construct schematic SMZ maps for different frequency ranges. Another advantage of the proposed of seismic microzoning method is that it eliminates the requirements for the synchronic microtremor measurements on the studied and reference soils. Moreover, the fact that there is simply no need for reference soils is a prerequisite for the method. The local vulnerability can therefore be assessed using only one seismic recorder with a 3-component sensor ignoring the location of microseismic motions sources and their characteristics variation over time.