The Landers earthquake of 1992?

Question

Here's something interesting I found.

"Its M(w) 6.1 preshock and M(w) 6.2 aftershock had their own aftershocks and foreshocks."

How is it possible for a foreshock and an aftershock to have its own foreshocks and aftershocks (I know the aftershocks of aftershocks are secondary aftershocks)?

Answer 1

From USGS:

Landers, California

1992 06 28 11:57:34 UTC

Magnitude 7.3

Big Bear, California

1992 06 28 15:05:30 UTC

Magnitude 6.5

The Big Bear quake was initially thought to be an aftershock of thee Landers quake, but later determined to be a separate event on a different fault line, triggered by the Landers quake.  The USGS summary doesn't mention the 6.1 foreshock, but does list another quake in the region some 2 months prior: 1992 04 23 - Joshua Tree - M 6.2