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, groundpenetrating radar (GPR) sensing, etc. At the same time seismic properties of soils (mainly velocities of p- and swaves) 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-geologicaldata, 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.