This was an aftershock of the Landers earthquake of 1992 -- the last of its aftershocks to reach magnitude 5 (the last M 5 aftershock previous to the Calico earthquake was in August of 1993). It occurred outside of Barstow, in the Calico Mountains (near both the Calico ghost town and the archaeological site which bears the same name) along the northern end of the Calico fault, one of many faults that experienced triggered slip during the Landers quake.