On the Multimodel Nature of Earthquake Sources and Their Prediction: the Baikal Rift Zone Case Study

Abstract

—As is known, earthquake sources result from destructive geological processes within the Earth’s lithosphere. As part of an international collaboration, we conducted a detailed petrophysical, geological, and structural study of the preparation conditions for exhumed paleoseismic ruptures in the Baikal Rift Zone and Mongolia. Alongside routine seismological data analysis, we utilized numerical simulations and physical-mechanical experiments on fault segments for medium-term forecasting and seismic hazard assessment. Methodologically, particular attention was paid to the influence of fluid-mechanical processes on both the occurrence of coseismic displacements in fault zone segments and the subsequent healing of these displacements at various crustal depths. Synthesizing the collected data and incorporating global data on the variety of geodynamic regimes of earthquake preparation, we identify a significant diversity in the thermodynamic factors governing crustal failure, accounting for fluid saturation within intraplate environments and interplate boundary zones. We analyze the key role of fluid flows at different crustal depths, where their influence largely dictates the observed variety of geomechanical conditions during earthquake source preparation. Furthermore, we consider the seismogeological features governing the nucleation of local earthquakes with magnitudes M ≥ 5.5 across various segments of the Baikal Rift Zone. Accounting for the totality of these factors improved the accuracy of medium-term forecasts for hazardous earthquake sources to 70%. Ultimately, these findings substantiate the advantages of constructing and implementing regional models of earthquake source preparation that comprehensively incorporate local seismogeological conditions.