On the Use of Medium-Term Forecast Data for the Baikal Rift Zone in Seismic-Hazard Assessments

The article presents the general results of medium- and long-term forecasting of earthquakes with K ≥ 13 (M ≥ 5.0) in the Baikal rift zone. These results have recently been obtained through the joint use of the geoinformation system for predicting the preshock stage of earthquake preparation and its associated two-stage phenomenological model. This model was created based on the analysis of seismological data on the preparation of the most dangerous earthquakes that occurred in the Baikal rift zone. It is consistent with the results obtained in studies of seismic regimes of ice shock preparation on the Baikal ice cover and in conducting full-scale experiments on fault sections with the aim of clarifying physical and mechanical conditions for the emergence of the sources of seismic-induced oscillations.The paper provides an example of practical use of results obtained for earthquake forecasting, as well as the ways of refining seismic hazard assessments relative to the infrastructure in the city of Angarsk 100 km away from the seismically hazardous Main Sayan Fault (MSF), whose zone reveals a “locked” segment with a seismic gap during the seismic regime analysis. In accordance with its linear dimensioning which represents a length of 60 km, two L/M equations served as a basis for potential energy calculations whose maximum values correspond to Mmax 7.1 and 7.8. It is shown that the use of the obtained earthquake-forecast results assists in refining the level of seismic hazard for the nearest time intervals of expected earthquakes with different Mmax values. Consideration is being given to the example of assessing the current seismic hazard using a medium-term forecast for the infrastructure of the city of Angarsk for the probability of seismic shaking from the southeastern section of the MSF zone for the next 10 and 50 years. The comparison with the OSR-16 map showed that the calculations carried out indicate a relatively lower level of seismic hazard for the city of Angarsk for 10- and 50-year expectation periods.