Assessing Gray Zone Risks in East Asia: A Threat Classification Framework Using Taiwan's ADIZ as a Case Study

Gray-zone activities have become a central feature of security competition in East Asia, particularly in the Taiwan Strait, where persistent military operations blur the boundary between coercion and armed conflict. This study develops a structured threat-assessment framework for evaluating the intensity of PLA aerial gray-zone pressure around Taiwan's Air Defense Identification Zone. Using principal component analysis, it constructs a four-quadrant classification model integrating aircraft capability, flight distance, angle of entry, and proximity to politically sensitive areas. The findings show that PLA aerial activities vary not only in frequency, but also in operational composition and spatial configuration. The framework distinguishes externally triggered power projection, low-capability spatial probing, routine low-intensity presence, and Taiwan-focused coercive pressure. Grounded in the Taiwan case, the approach offers a conditionally transferable framework for examining repeated and spatially observable gray-zone military activities in other regional contexts.