Abstract: The continuous advancements in energy transformation has led to a tight coupling between power and natural gas systems, enabled by gas-fired units and electricity-driven gas facilities. In the face of unconventional disasters, bidirectional coupling between these systems may cause faults to propagate across the energy system, thereby exacerbating blackout crises. A notable example occurred in February 2021, when Texas, United States, experienced a chain failure between its power and natural gas systems due to extremely cold weather, resulting in significant losses and adverse social impacts. This study begins by analyzing the root causes of large-scale blackout events in Texas from the perspective of power-gas coupling. Subsequently, a power-gas coupling system is constructed, and an event-triggered information interaction mode is employed to examine the fault propagation process of the power-gas coupling system during extreme events through co-simulation. Finally, a fault-blocking strategy is proposed, with the simulation analysis demonstrating that this approach effectively suppresses fault propagation and enhances system defense.