Active fault

An active fault is defined as a plane or slightly oblique fracture of the earth's crust along which tectonic displacements can occur.

A fault can be considered as active if it has been seismically active at least once during the Quaternary period, or if it shows evidence of current displacement.

The consequences of an active fault

When an active fault at the origin of an earthquake opens at the surface:

• it can cause movements along the rupture line (with rupture of the ground at the surface);
• it can also generate local vibratory movements in a very close zone of a few hundred metres either side of the rupture line; this effect can lead to both horizontal and vertical amplification.