Abstract
For purposes of seismicity microzonation of the Ulan‐Ude city territory, engineering geophysical studies are conducted to reveal which types of rocks and soils are dominant in the study area and to classify them by site‐specific velocities of P‐ and S‐waves and amplitude‐frequency characteristics. The article describes a technique for establishing the baseline seismic signal corresponding to parameters of relatively strong earthquakes in potential earthquake foci (PEF) zones. It is shown that the established baseline signal is applicable. Presented are results of theoretical calculations based on seismicity‐soil models providing reference parameters of bedrock, medium and water‐saturated soils (soil categories 1, 2 and 3, respectively). Seismic impacts are assessed for the zone with the baseline seismic intensity of 8 points, as per MSK‐64 seismic intensity scale. The reference model is used to identify zones with seismic intensity from 7 to 9 points in the city territory, and it is established that such zones differ in thickness of water‐saturated and non‐water‐saturated soil layers. As a result, a schematic map showing the main parameters of seismic impacts is constructed in the first approximation. The obtained data are useful for the development of recommendations concerning further engineering seismological studies and activities for the appropriate revision and upgrading of the seismic microzonation technique in order to complete seismic microzonation of the Ulan‐Ude city territory.
Highlights
The city of Ulan‐Ude is located in the seismically ac‐ tive region of Russia
SNiP II‐А.12‐69* was replaced by SNiP II‐7‐81, and the base‐ line seismic intensity for Ulan‐Ude is estimated at 8 points [The USSR Seismic Zonation Map, 1984] which assumes the recurrence of a major seismic event every 1000 years, according to Map (B) under SNiP II‐7‐81* [SNiP..., 2011]
In the cur‐ rent stage of our studies, we analyze dynamic characte‐ ristics of perceptible earthquakes that occurred in the study region, establish seismic signals corresponding to the baseline seismic intensity, develop the seismi‐ city‐soil models, try to forecast seismic impacts with re‐ gard to different construction conditions and classify zones in the Ulan‐Ude city territory by the seismic impact parameters
Summary
The city of Ulan‐Ude is located in the seismically ac‐ tive region of Russia. According to [The Map..., 1999], the city's territory with medium soil conditions is cha‐ racterized by seismic intensity of 8, 8 and 9 points (as per MSK‐64 seismic intensity scale) and three levels of seismic hazard with 10 % (A), 5 % (B), and 1 % (C) probabilities of exceedance in 50 years. SNiP II‐А.12‐69* was replaced by SNiP II‐7‐81 (in force since 01 January 1982), and the base‐ line seismic intensity for Ulan‐Ude is estimated at 8 points [The USSR Seismic Zonation Map, 1984] which assumes the recurrence of a major seismic event every 1000 years, according to Map (B) under SNiP II‐7‐81* (updated revision) [SNiP..., 2011] It is envisaged by the current construction regula‐ tions and standards that optimal locations must be se‐ lected for construction projects with account of seismic resistance calculations, which necessitates quantifica‐ tion of the main parameters of seismic impacts that may be imposed to foundations of building and facili‐ ties. To achieve the objective of seismic micro‐ zonation mapping of the Ulan‐Ude city, it is required to update the general seismicity zonation data and assess levels of seismic hazard for new construction project areas in the city. A technique for construction of a new seismicity micro‐ zonation map of the Ulan‐Ude city territory is justified
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