For a long time, the causes and triggering rules of giant subduction earthquakes (≥ magnitude 9) have remained a major research challenge in the field of Earth science. Traditional plate tectonic theory fails to explain their correlation with solar activity, the origin of shear force, as well as the periodic evolution and transmission mode mutation of the circum-Pacific seismic chain. Based on first principles, this study systematically elaborates on the four-dimensional coupled triggering mechanism of giant earthquakes involving the "sun-atmosphere-ocean crust" system, integrating nearly 50 years of observational data on atmospheric thickness, sunspots, oceanic fluids, and crustal mechanics, as well as long-term circum-Pacific seismic chain data from 1700 to 2026. The core logic of the conclusion is as follows: the solar wind (which controls atmospheric mass) serves as the power source, atmospheric unloading (decreased pressure) acts as the trigger, the rapid uplift of oceanic plates and the slow filling of the resulting space by continental plates (leading to relative displacement) constitute the specific process, and the final outcome is the subduction of continental plates beneath oceanic plates, thereby triggering giant subduction earthquakes. The study found that the solar sunspot cycle regulates the thermal state of the Earth’s stratosphere, which in turn alters the thickness of the near-surface atmospheric boundary layer and thus affects the distribution of surface pressure. As an incompressible fluid medium, the ocean can efficiently conduct pressure to plate subduction zones, while the rigid properties of continental plates result in a time lag in pressure conduction. Combined with the mutation of crustal medium mechanical parameters, this promotes the irreversible transformation of the circum-Pacific seismic chain from "elastic conduction" to "rigid conduction". During atmospheric pressure loading, oceanic plates bear greater pressure than continental plates, leading to stress locking. During atmospheric pressure unloading, the difference in rebound speed between oceanic and continental plates generates instantaneous shear force, triggering giant subduction earthquakes. Over the past 50 years, the basal thickness of the Earth’s atmosphere has shown a continuous upward trend, primarily due to the solar wind continuously transporting gaseous substances to the Earth, forming a netinflow of atmospheric mass. This shortens the cycle of atmospheric pressure loading and unloading, thereby increasing the frequency and shortening the interval of giant earthquakes in the circum-Pacific region. This study supplements historical data on atmospheric thickness and comparative data on giant circum-Pacific earthquakes and seismic chains. All conclusions are based on real observational data without any fitting assumptions or fictional concepts, establishing a complete closed-loop theory of "solar activity-atmospheric thickness-oceanic conduction-crustal stress-giant earthquakes" that perfectly aligns with the core observational facts of the circum-Pacific seismic belt, providing a new scientific basis for the explanation, prediction, and prevention of giant earthquakes.
Xiangsheng Yu (Sun,) studied this question.