An aftershock can be identified by both mechanical method and statistical laws.
The Wenchuan-Lushan earthquake sequence obeys three established statistical laws.
The 2013 Lushan event was triggered by the 2008 Wenchuan earthquake.
The Lushan event can be regarded as one of the aftershocks of the Wenchuan earthquake.
The hot debate on whether the Lushan event is an aftershock may be settled.