A “real-time” animation of the seismic (vertical) velocity of Italy’s 5.5 Mw earthquake that hit between the Aquila and Rieti provinces. The second half of the animation shows the whole country and surrounding area.
Real-time indicates that the video reflects how the waves propagated in real-time. It’s neither slowed down not sped up.
Red color indicates relatively higher vertical velocities indicating the ground is moving upwards while the blue color indicates the lower (negative) velocities indicated a downward movement of the ground. Color intensity refers to the magnitude.
An earthquake is the result of a sudden release of “strain” that is built-up between two tectonic boundaries or at a fault line*, usually slipping in opposite directions.
The following video by the California Academy of Sciences shows a computer simulation of an earthquake at the Hayward fault which is one and the most concerning of several faults in California. The most famous fault being the San Andreas fault.