Californians have been left unnerved by the official announcement of an imminent earthquake in the region.

The California Office of Emergency Services (OES) warned at the end of September that the south-west US State warned could be in for “larger earthquakes” following a series of smaller tremors that shook the Salton Sea area – just a matter of kilometres from the tightly wound San Andreas fault.

OES director Mark Ghilarducci said: “California is earthquake country. We must always be prepared and not let our guard down.”

A statement from the governmental group warned that “stresses associated with this recent earthquake swarm may increase the probability an additional earthquake as large, or larger, than the September 26 magnitude 4.3” which hit Salton Sea – the most powerful of 200 quakes to shake the region in the last week.