An earthquake occurs when tectonic plates move against each other, leaving cracks called faults. Energy is released at the seismic focus, where the rock breaks, creating seismic waves. The epicenter is the point on the surface directly above the focus, where shaking is most intense. Earthquakes can be violent enough to destroy cities. Japan has implemented measures like earthquake-proof building codes and research centers to study seismic activity and mitigate risks in disaster-prone areas.