From Daily Mail (caution: tabloid):
An underwater fault line along the US West Coast could trigger a megaquake that would be more devastating than California’s ‘Big One,’ a new study suggests.
Using underwater mapping techniques, scientists have mapped the Cascadia Subduction Zone – a 600-mile fault line extending from southern Canada to northern California – in never before seen detail. It has revealed that the fault splits into four segments instead of being one continuous strip like most fault lines. The discovery could prove more catastrophic because the tectonic plates can slide under each other, creating more pressure and more severe earthquakes.