Abstract: Natural locked segments dominate the stability of locked-segment-type slopes and the evolutionary process of tectonic earthquakes. They fail in order of bearing capacity from low to high. Therefore, it is very important to study the mechanical response mechanism of the next locked segment while the current locked segment is broken, and predict the fracture behavior of the latter. We found that a high-energy-level characteristic cracking event (characteristic event) at the volume-expansion point of locked segment can be viewed as both the indicator of the point and the precursor to the rupture of locked segment. We established a mechanical model consisting of two locked segments that are subjected to shear loading, discussed the mechanical behavior resulted from different combinations of locked segments' bearing capacity based on the theoretical analysis and numerical simulations, and stated that the mechanical action between natural locked segments follows a strong action mode. In other words, when the current locked segment is loaded to reach its peak-stress point, the load applied to it will be transferred to the next locked segment; the load transfer with a negligible increase in shear displacement or strain can make the latter evolve to its volume-expansion point. The mode can well explain many kinds of seismic observation phenomena and experimental results.