'More than 30 years' since earthquake of this size hit California: seismologist

John Cassidy is my guest John is a quake seismologist with Natural Resources Canada John good to see you appreciate you taking the time so quickly for this breaking news your reaction to what we're seeing what you know so far you Todd yes uh what you've outlined it's been updated now to a magnitude 7 earthquake and uh that is uh of course quite a bit larger than a 6.6 it was felt over a very large area of Northern California San Francisco up into the Oregon region um and the tsunami warning that's been issued for uh Northern

California coastline the Oregon Coastline uh this earthquake was on what we call a strike slip fault where plates are sliding past one another it's not the San Andreas it was about 60 kilometers offshore um and so that helps because it's further away from population centers and the sort of movement that we see is is uh less likely to cause a major tsunami but any earthquake of this size can trigger landslides beneath the ocean or landslides on Shore that can cause localized tsunamis uh so it's really a you know watching to see at this point and

and getting people away from the coastline um at at this point so it's um very significant earthquake it's been more than 30 years since we've seen an earthquake of this size uh in this region of Northern California yeah can you tell me how seismically active uh that part of the US is John yeah it's it's one of the most seismically active it's it's as I mentioned it's not the San Andrea's fault but it's um it's the southern end of what we call the Cascadia subduction zone where ocean plates uh are being pushed beneath Northern California

Oregon Washington and here in southern British Columbia as well so it's a part of a very large uh plate tectonic system where ocean plates are moving towards the continent so it is um it is extremely active we see magnitude four and five earthquakes on a regular basis along that fault Zone where today's earthquake occurred um the big magnitude sevens are are you know not as common but every 20 30 years uh we see those large larger offshore earthquakes yeah we were showing some Chopper if we can go back to it John while you're with us

here uh of what it looks like uh along the coastline and you know you see you know people and you see cars I'm just wondering how it works here sort of in layman's terms um you know when when you're talking about a tsunami warning because you know we know that the Quake happens off the coast and the water will pull out and then it will come back correct right so sometimes the first arriving wave is uh uh is is a large amplitude wave coming in but sometimes it's the the water receding and and that also

is an indicator of a tsunami so um anytime you feel strong shaking and you're near a coastline know in this case Northern California you really want to move away from from the coast uh and the other thing with the tsunami it's not a single wave it's a series of waves that can continue for many hours and the first wave may not be the largest uh it could be the second or third or fourth wave so you it's really important to move away from the coastline and to stay away from the coastline until you hear from

um from authorities that it is uh safe to to return so it's um you know it's many hours it's over many hours and it's uh uh and way and the impacts can vary drastically along a coastline depending on um the Beth themetry of the ocean the seafloor and topography local topography so it can really vary a lot along the coastline John Cassidy joining us from Victoria on Vancouver Island John is a seismologist with Natural Resources Canada John I appreciate you getting into place and coming on the show and joining us as we're following this breaking

news out of California thanks so much thank you Todd