A DEVASTATING 9.3 magnitude earthquake powerful enough to unleash a tsunami could strike the west coast of America after a series of tremors on a major fault line. 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