Application of microseismic and calculational techniques in engineering-geological zonation

Abstract

Data on engineering-geological conditions is the basis for seismic microzonation (SMZ). It is usually based on different data of field geological works in the investigated area, including drilling data, ground-penetrating radar (GPR) sensing, etc. At the same time seismic properties of soils (mainly velocities of p- and s-waves) are obtained by seismic exploration. This technique is used for typical sites. While the quality of initial engineering-geological map strongly affects selection of such "typical" sites. Practice of seismic microzonation has shown that such maps must be refined before usage of the main SMZ techniques (earthquakes and explosions recording, etc.) which are relatively labor-intensive. For practical realization of SMZ in the Republic of the North Ossetia-Alania we had to use combined microseismic technique to refine engineering-geological-data, especially in instrumental "gaps" regions. As a result new statistical method for different site type allocation was developed. It is based on histograms of different site parameters, obtained from microseisms processing. Mobile seismic stations was used to investigate large areas in a short terms, exploration grid size was from 100 up to 500 meters in some places. H/V technique was used for predominant period estimation. Numerical models were used for data control in reference sites. As a result new refined engineering-geological maps of Vladikavkaz, Beslan, Alagir, Ardon and other cities were obtained in a short time.