How long does it take to form a earthquake?

Answer 1

An earthquake is the sudden release of energy between rock masses deep underground. The pressure can build for minutes, days, or many years. Eventually the rocks will move in response to the pressure, resulting in disruption of rocks around them (and especially above them). Earthquakes are the motion associated with these movements, and normally are from a few seconds to a minute in actual length, followed by "aftershocks" or response movements from the affected rock masses.

Answer 2

An earthquake usually occurs when tension and pressure in the bedrock becomes so great that suddenly a fracture forms. The slippage sends a shock wave that causes structural damage to buildings, avalanches, mud slides, etc.