Integrated Workflow with Static and Dynamic Geomechanical Modelling for Fault Critical Re-Active Stress Evaluation

Abstract The Songliao Basin, a vast sedimentary basin located in Northeast China, extends in a north-northeast direction, covering the Heilongjiang, Jilin, Liaoning provinces, and the Inner Mongolia Autonomous Region. It spans approximately 750 kilometers in length and 330-370 kilometers in width, encompassing an area of 260,000 square kilometers. The internal topography of the basin predominantly features uplifted areas to the north, northeast, southeast, and southwest, a gentle slope to the west, and a significant depression in the central region. Cenozoic sedimentary rocks in the Songliao Basin have a cumulative thickness exceeding 6000 meters, with Cretaceous deposits being particularly thick and widespread. The basin's geologic structure is complex and heavily faulted, enriched with geothermal, solar, and mineral resources, hence presenting a favourable environment for inducing seismic activity. Therefore, assessing the stress characteristics and susceptibility to sliding of geological structures in the Songliao Basin holds paramount importance for earthquake mitigation and disaster prevention. This study involved statistical analysis of data from 19 boreholes, 65 hydraulic fracturing experiments, and 44 stress relief measurements from the basin and adjacent areas. The study also discusses fault slip potential and seismic hazards based on fault mechanical theories such as the Byerlee-Anderson theory. Results indicate a shift from compressive (thrust) to transcurrent (strike-slip) stress regimes, aligning with the distribution of high-angle right-lateral NNE-trending reverse faults within the region. The dominant orientation of the maximum horizontal principal stress ranges between N45° and E60°. Preliminary inversion results suggest a primary compressive stress regime with localized strike-slip characteristics, which corroborates the inversion results from focal mechanism studies. The average friction coefficient of the faults in the region is calculated at 0.41, indicating a state of stability and low susceptibility to fault slipping. Additional analyses, interpolating lateral pressure coefficients and stress accumulation indicators, uniformly suggest a low general predisposition for fault slipping, although localized higher levels of stress accumulation are observed in shallow fault zones. Our comprehensive analysis infers that faults are more likely to slip in a NW-SE orientation.