Vancouver Island is vibrating, but you won't feel a thing
Monday, May 14, 2018, 7:37 PM - Many kilometres below the surface, a subtle process is occurring along a fault boundary buried deep under Vancouver Island. These faint vibrations are measured in small changes in direction under the crust, but the implications could be devastating.
Since 2003, scientists have been activity studying the mysterious seismic rumblings below the surface, but they're not traditional earthquakes; subsequently, they're not measured using solely traditional seismographs (shows up as background noise), but sensitive global positioning systems (GPS) are used as well.
All this action is occurring in the Cascadia Subduction Zone, the infamous plate boundary where the Juan De Fuca Plate is diving under the North American Plate.
And, this is where we focus on the tiny vibrations many kilometres below the surface. Look at the hundreds of tiny vibrations that have been ongoing across Washington State, confirming the ongoing ETS:
The relationship between the plate of Juan De Fuca and the North American Plate is a tumultuous one; they're in fact relatively locked in place, and every 14 or 15 months, an Episodic Tremor and Slip (ETS) event relieves some of this stress, in the order of a few centimetres of slip motion (westward) over several weeks.
It's no secret there's a fairly substantial ferry ride from Vancouver Island to the Lower Mainland, but it's getting marginally closer over the past several decades. Although, the time taken off the ferry ride has been pretty negligible, so don't look for any price adjustments.
During these ETS movements, the direction of motion of Vancouver Island reverses and moves westward, bucking the overall eastward trend. But, these incremental movements will be irreverent in the event of a massive earthquake, which would shift Vancouver Island westward, erasing these modest gains made, inching towards the Lower Mainland.
The research has been a success, as it highlights the extent of where a megathrust (>8.0 magnitude) earthquake may occur, and also in fact, may help with earthquake prediction in the future.
But there's a drawback. These events do put additional strain along the fault, so there's a slight increase in the threat of a major earthquake during an ETS event. For reference, the last major earthquake occurred in 1700, and they're on average every 500-600 years.
In closing, there's no need to panic, the odds are extremely low that an earthquake will occur during this current ETS cycle, but it's great for awareness and a gentle reminder – to be prepared with an earthquake kit.