The current earthquake situation in California is not stable yet. Series of tremors on a major fault line could be a warning of a bigger one.
Emergency services are already preparing for how to deal with a terrible off-shore earthquake in the Cascadia Subduction Zone, off the west coast of America near California.
They were just completing their four-day major emergency test run when a 5.2 magnitude quake hit Borrego Springs, San Diego County, in California on Friday.
The mid-sized earthquake caused more than 200 aftershocks – some more than three on the richter scale – and could be felt from Santa Barbara to the Mexican border.
Egill Hauksson, a research professor of geophysics at Caltech, said of the 5.2 quake: “It was the biggest one for a while.
A 3.1 magnitude quake followed yesterday, 14 miles from Borrego Spring according to the US Geological Survey (USGS).
And in the last 10 days there has been nine earthquakes of magnitude 3 or greater nearby according to the USGS, leading to fears of what may be to come.
The quakes have taken place on the San Jacinto fault, the region’s most active, Mr Hauksson said.
Scientists say both the California fault lines and the Cascadia Subduction Zone are long overdue a major earthquake of magnitude eight or above.
In a statement after the Cascadia Rising emergency tests a spokesman said: “Subduction zone earthquakes are said to be among the most powerful, and can exceed a 9 magnitude.”
Scientists at the USGS have revealed their computer modelling tests indicate the San Andreas Fault in California is capable of producing earthquakes of a maximum magnitude of 8.3.
This is still of concern as the 1906 earthquake that devastated San Francisco had a lower magnitude of 7.9.
But they have revealed the Cascadia Subduction Zone is of most concern. It runs about 60 miles offshore along the Pacific coast from northern California to Vancouver Island, so major cities including Portland, Seattle and Vancouver are within its tsunami range, threatening millions of people and major infrastructure.
The USGS has worryingly confirmed the same computer models show it is capable of producing an earthquake with a magnitude up to 9.3, which would likely trigger huge tsunami waves.
This would be more powerful than the magnitude 9 tsunami-causing quake that hit Japan in 2011, claiming thousands of lives and taking out nuclear reactors.
Worse still, many scientists say the US is not yet prepared to deal with such a natural disaster, and it could strike at an time.