**An Instability-Phase Framework for Injection-Induced Seismicity: Integrating Pore Pressure Evolution, Rate-and-State Nucleation, and Dynamic Energy Constraints**

This preprint presents a conceptual mechanical framework for interpreting injection-induced seismicity through a hierarchical instability-phase structure. The study integrates pore-pressure diffusion, Coulomb stress evolution, rate-and-state frictional nucleation theory, and dynamic fracture energy constraints into a unified analytical inequality defining escalation conditions. Rather than providing site-specific forecasting or operational hazard prediction, the work formalizes necessary mechanical thresholds governing the transition from pressure-triggered slip to dynamically sustained rupture. The framework distinguishes triggering probability from structural magnitude capacity and emphasizes the dominant role of fault geometry and stress conditions in magnitude scaling. The manuscript includes extended mathematical derivations of pressure-dependent nucleation length, dynamic energy release thresholds, and combined escalation inequalities. Illustrative numerical relationships are presented for conceptual demonstration only. No field calibration or deterministic hazard claims are made. This version (v1.0) represents the initial public release dated 11 February 2026.