The experience of detailed probabilistic assessments of possible seismic effects on the territory of North Ossetia-Alania

Abstract

Relevance. At present, in many seismically active regions of the Russian Federation (including the territory of North Ossetia-Alania), there is a certain deficit of accurate and detailed data on possible seismic effects on these territories. In addition to the fact that without these data many academic problems of engineering and general seismology cannot be solved, they are also necessary to ensure the proper quality of earthquake-proof design and seismic risk predictions. These data is also necessary to make effective management decisions and other measures to protect the population, infrastructure and the environment from possible strong earthquakes. Therefore, the present study aimed at reducing the deficit of such data in the seismogeological conditions of North Ossetia-Alania is relevant. Aim. Improvement of the methodology and obtaining, on this basis, more accurate and detailed probabilistic estimates of the ground vibration parameters used in engineering and seismological practice during earthquakes, which are dangerous for the territory of the Republic of North Ossetia-Alania. Methods. The work was carried out using an original probabilistic technology for seismic hazard assessment, which includes the development, based on the analysis of a large amount of experimental data on instrumental registration and macroseismic description of earthquakes in the Caucasus and other seismically active regions of the world, regional models of strong ground motion and seismicity with subsequent calculations (based on the formula for complete probabilities) of the resulting characteristics of possible seismic effects on the studied territory. Results. For the first time for the studied territory, from a unified methodological standpoint, refined probabilistic estimates of a wide range of parameters (macroseismic intensities, amplitudes, periods, durations, spectra and accelerograms) of ground vibrations were obtained for possible earthquakes in a given territory with average recurrence periods of 500, 1000, 2500 and 5000 years, which in some cases differ significantly from the current standards. For example, it has been shown that in the considered territory the predicted amplitudes and spectra of ground accelerations within the same magnitude zone can differ significantly (up to 100%) depending on the recurrence periods of expected earthquakes. The probable response spectra of ground vibration accelerations, depending on the frequencies of the spectral components, can also significantly (up to 100%) differ from the standard spectra.