This is according to scientists who took measurements from the fault over two decades.

Reporting in the journal Nature, the team found that small "repeating earthquakes" became more frequent as the San Andreas Fault weakened.

This pattern, they say, could help to forecast earthquakes in the future, something that is currently impossible.

It is possible that the strength of faults and earthquake risk is affected by seismic events on the other side of the world

Samoa and Sumatra have suffered earthquakes within 16 hours of each other. This is a cause and effect and not a terrible coincidence.

The contiguity of the Earth's Tectonic Plates facilitates a concatenation of seismic events whose resultant vector may well be found in a faultline so far removed from the origin, that it may appear to be totally unrelated.