Cascadia Eq Sources

The title of this short article definitely caught my eye…”Will a megathrust earthquake strike the NW in 2013????” It brought up several things…such a quake would be incredible destructive, no doubt killing thousands and costing billions in damages. Has earthquake predictions improved significantly recently? What the heck is going on up there in the northwest!??!?!?!

Well, it turns out there were 4,800 earthquakes in the Northwest in 2012 and a record “episodic tremor and slip” (ETS) events – a string of deep mini-quakes running from Vancouver Island to below Centralia – over the summer.

The Range And Path Of The Record 2012 Episodic Tremor And Slip Event. Photo: Pacific Northwest Seismic Network
The range and path of the record 2012 episodic tremor and slip event. Photo: Pacific Northwest Seismic Network

A devastating megathrust earthquake can happen every 300 to 500 years in this region – that is caused by the Juan De Fuca plate’s collision and subduction with the North American plate.  The boundary between the Juan De Fuca plate offshore and the North American plate runs under the Puget Sound area from California up to Canada. This is where a megathrust quake of magnitude 9 or better could occur. Below that danger zone, deeper in the subduction, is where the ETS happens.

Here Are The Locations Of All Events Larger Than Magnitude 3 In 2012. The Earthquakes Are Spread Across The Region, Mostly On The Western Side. The Largest Event Of The Year Was A Magnitude 4 Less Than A Mile Inside Washington State Near Victoria, B.c., In December.
Here are the locations of all events larger than magnitude 3 in 2012. The earthquakes are spread across the region, mostly on the western side. The largest event of the year was a magnitude 4 less than a mile inside Washington state near Victoria, B.C., in December.

However, the question remains: Are these events (ETS) associated with earthquakes and if so, how? A researcher is building computer models to find answers and so far has some preliminary results that suggest the tremors and slips are in fact connected to quakes. In his simulations, after a big earthquake, the events stop for about 100 years and then start up again. And then one of them eventually will “spontaneously grow into a fast, dynamic rupture” – an earthquake. The problem is he can’t tell which one will mutate into disaster. The hope is to find something that will “tip them off” that something big is about to occur.

The article raised the question does any of this mean we’re likely to see the “big one” in 2013 and then immediately notes that “it is still impossible to predict, however some clues may be emerging.” So in other words…stay tuned – who knows!?!?!

In other words, operation attention, get ready now and be ready.