An earthquake begins when the plates push against earth other and the pressure builds. Cracks start to appear in walls and roads.
EQs occur at all times of day.
There have been damaging EQs both in the a.m. The plates are thought to slide past one another, sometimes as much as a few inches a year. If the plates do not move smoothly, tension may build up between them. Suddenly, the plates move, and this is an earthquake. One such border, known as a fault line, is in California, and it is called the San Andreas Fault.