Problems of Engineering Seismology: article

Аnnotation: The efficiency of method of microseisms for seismic microzonation (SMZ) is discussed based on the experimental field data in different geological conditions. Method of microseisms is in the list of recommendations and codes and is widely used because of its low cost. In the SMZ microseisms are used for assessment of the increment of the intensity of shaking through calculation of amplitude spectra at seismic stations and resonance characteristics of ground layers usually in combination with other methods. Difficulties in taking into account for numerous local sources of noise may considerably reduce the accuracy of the results. This has to be considered when planning the field works for each object (site). In some cases (high anthropogenic noise level) it is better to retain from using the spectral amplitude ratio in high frequency band (above 3 Hz). Calculation of intensity increments separately in 0.5–2 Hz and 2–3 Hz bands with assuming as final increment the maximum of both calculations guarantees due level of conservatism and, hence, the method microseisms is applicable for critical facilities too. Spectral ratio of horizontal and vertical components of seismic motion (H/V) can be used for assessing resonance characteristics of soils and structure of the upper part of the soil profile, in particular, evaluation of the depth of the soil/bedrock boundary.