What is an earthquake and how is its strength measured?
Really, the answer to your question is simply: Plate Tectonics. Read below for details. Earthquakes: It all comes down to stress and strain from the interaction of different plates, chiefly at the boundaries. It is not ‘the plates rubbing together’ as many people say; or at least that’s a very simplistic view. Plate tectonics causes stress on the continents and oceans, all over the surface of the earth. In some places, the stress is very small (usually within the plates). Elsewhere, the stress is high, usually where the plates meet each other. Since each plate moves, when two come in contact, they stress each other. They can push on each other and cause compressional stress, they can pull with extensional stress, and they can slide past or shear each other with tensional stress. Faulting, causing earthquakes, comes from the fact that this stress is building up all the time, but rocks and continents are strong materials. Just like hitting a rock with a small hammer, you do put stress on
