Earthquakes occur when crustal plates move due to heat from Earth's core. Tectonic plates form around Earth's core, meeting at faults. About half-million earthquakes happen daily, most are too small to feel. Epicenter is the surface point where earthquake starts
Circum-Pacific Belt (Ring of Fire) contains 81% of world's largest earthquakes. Alpine belt stretches from Java to Sumatra through Himalayas and Atlantic. Mid-Atlantic Ridge marks plate divergence, including Iceland