Scientists are warning that an earthquake could be heading to California, as recent research suggests that seismic pressure in two big fault lines is the highest at any point over the last 1,000 years.
The new paper, published in the Journal of Geophysical Research, does not predict when a quake will strike. But it finds the southern San Andreas and San Jacinto faults are now carrying more pent-up stress than at any point in the past millennium – a state the authors call "critically loaded".
California's last earthquake on a similar scale was the magnitude-7.9 San Francisco earthquake of 18 April 1906, which killed around 3,000 people and devastated much of the Bay Area.
But while that disaster unleashed enormous amounts of energy, it did so on the northern San Andreas Fault. The southern fault systems examined in the new study were unaffected.
Because earthquakes in one part of the fault network do not relieve pressure elsewhere, researchers say these southern sections have continued accumulating strain for decades – and in some places centuries.
