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

Abstract

The article presents the general results of medium- and long-term earthquake forecasting with K ≥ 13 (M ≥ 5.0) in the Baikal rift zone. They were obtained in recent years through the joint use of the Prediction geoinformation system and the developed two-stage phenomenological model for the periods of preshock preparation of earthquakes. This model was created based on the analysis of seismological data on the preparation of the most dangerous local earthquakes that occurred in the Baikal rift zone. It is consistent with results obtained in the study of seismic regimes of ice shock preparation on the ice cover of Lake Baikal and in conducting field experiments on fault sections with the aim of clarifying the physical and mechanical conditions for the emergence of sources of seismic-range wave-oscillation generation. The paper provides an example of practical use of the obtained results of earthquake forecasting, as well as methods of clarifying seismic-hazard assessments in relation to infrastructure in the city of Angarsk, located 100 km from the seismically dangerous Main Sayan Fault (MSF), in the zone of which, during the analysis of the seismic regime, a “locked” segment with a seismic gap was identified. In accordance with its linear dimensions with a length of 60 km, according to two assumed equations of relationships L/M, estimates of energy potential were calculated, the maximum values of which correspond to the values M_max = 7.1 and 7.8. It is shown that the use of the obtained earthquake-forecast results helps to clarify the level of seismic hazard for the nearest time intervals of expectation of earthquakes with different values M_max. An example of assessing the current seismic hazard using a medium-term forecast for the infrastructure of the city of Angarsk is considered for possible seismic tremors from the south-eastern section of the MSF zone for the next 10 and 50 years. When compared with the OSR-16 map, it is shown that the calculations carried out indicate a relatively lower level of seismic hazard for the city of Angarsk, with waiting times of 10 and 50 years.