In the last two days there have been three significant earthquakes off the coast of Oregon. Fortunately there have been no tsunami alerts as a result. But these quakes are reminders of the ever-present and enormous Cascadia Subduction Zone, a fault that runs from northern California to Vancouver Island.
The Cascadia Subduction Zone is not that different from the fault where the 8.9-magnitude (Richter scale) earthquake occurred creating a devastating tsunami that wiped out a large portion of the island of Japan. Both faults run along the coastline about 100 miles offshore.
The three recent earthquakes off the Oregon coast were centered on the Cascadia Subduction Zone. They ranged from 5.5 to 6.0 in magnitude and there are over a hundred such earthquakes (less than a magnitude of 7.0) globally each year. As such they could be considered strong quakes but not “major.” Major quakes (7.0 and greater) occur 10 to 20 times per year with 9.0 earthquakes happening once every 10 to 50 years.
Do you know what will happen and what to do when there is an offshore earthquake and a tsunami warning is issued as a result? The following have been compiled from multiple sources:
- There will be an official tsunami evacuation siren
- Alerts will be issued on NOAA radio
- Emergency telephonic warnings will be issued
Know what to do
- Stay off the phone and do not call 9-1-1. Tying up phone lines slows down the notification process.
- Listen to NOAA and local radio stations for latest emergency information.
- Get to higher ground (at least fifty-feet above sea level).
- Climbing to higher ground is preferred but if you must drive do so carefully so not to create problems that will slow down evacuation.
- Return to lower ground only when advised to by authorities that it is safe to do so. A tsunami is a series of waves that may continue for an hour.
Know where to go
How will you know where to go when you hear the warnings? It depends on where you are. The Washington Department of Natural Resources has produced these brochures with maps to have at the ready.
Head uphill away from the shore on any side of the island. If it is a distant earthquake and you have time, drive to Beach School or the Lummi Island Grange which are designated assembly areas.
Ferndale and Lummi Nation
Fortunately, most of the Lummi Nation land is considered “high ground.” If you are near shore, head inland.
But if you are south of Douglas Road and near the Nooksack or Lummi Rivers, you are in the lowlands and at greatest risk in the event of a tsunami. Check the map below (from the Washington DNR brochure) to identify your evacuation routes from the area to higher ground.