seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves. earthquakes are caused mostly by rupture(破裂, 裂开) of geological faults(断层), but also by volcanic activity, landslides, mine blasts, and nuclear experiments.

　　an earthquake's point of initial rupture is called its focus or hypocenter. the term epicenter means the point at ground level directly above this.

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