<p>Geological CO₂ storage is a key strategy for reducing atmospheric carbon emissions, where long-term containment depends on understanding subsurface migration behaviour. Fault zones are critical geological structures that can strongly influence CO₂ transport and potential leakage pathways. However, the observable physical responses associated with CO₂ migration within fault-controlled formations remain insufficiently understood. This study develops a large-scale three-dimensional physical similarity model to simulate CO₂ injection into a fault zone, with synchronous strain–temperature monitoring and supplementary apparent resistivity measurements. The aim is to interpret these measurable multi-field responses as indicators of CO₂ migration behaviour rather than to assess fault mechanical stability. CO₂ injection induces deformation and thermal responses, while apparent resistivity anomalies provide additional evidence of pore-pressure redistribution, fluid displacement, and gas–water interactions. The integrated strain–temperature responses, supported by apparent resistivity observations, suggest a staged migration process comprising pressure-driven expansion, transitional gas–water redistribution, and final stabilization accompanied by gradual fluid redistribution and thermal equilibration. Migration is predominantly concentrated along the fault zone, which appears to provide a preferential vertical pathway for CO₂ transport, while lateral diffusion into surrounding strata remains limited. The results suggest that the combined multi-field observations can help identify migration pathways and stage evolution, providing process-based support for interpreting monitoring signals in fault-affected storage systems. These findings should be interpreted as process-scale insights into fault-controlled CO₂ migration rather than direct quantitative predictions for deep geological storage environments.</p>