Monday, October 29, 2012

Tsunami Strike! Port Angeles (not) inundated

Compared to the "perfect" storm brewing on the east coast, the 7.7 quake that hit off of the coast of Haida Gwaii this weekend has received only limited attention. The West Coast and Alaska Tsunami Warning Center issued a tsunami warning for the northern part of B.C. and some of Alaska 30 minutes after the 8:04PM earthquake. By 1009PM, the alert had been extended as a "warning" for parts of Hawaii, and then at 1044PM, the alert had been extended at an "advisory level" for parts of the California coast (see this page for a description of the 4-tier tsunami alert system). The coast of Washington in general (including the Pacific Ocean and Strait of Juan de Fuca coasts of the Olympic Peninsula) were only included in the center's alerts at a "for information only" status.

But we did get "hit"...check out these water level data from the NOAA tidal gauge in Port Angeles Harbor:

A wave train of successive ~6 inch waves every 15 minutes for close to 8 hours, starting in earnest around 11pm on Saturday. Clearly, this tsunami posed no risk to communities on the Olympic Peninsula, but such an event always gives one pause...are we ready for a worse-case scenario?

There is a clear difference between the two "types" of tsunami we can expect on the Olympic Peninsula. A "local" tsunami would be very obvious, because it would be preceded by an earthquake that would, most likely, be at least strong enough to knock us off of our feet. Our tsunami warning system for such an event is built-in...if you are knocked off your feet then, if you are able, get to high ground as soon as possible after you can stand up again. For low-lying communities, or parts of communities, the planning that needs to happen is around escape routes, knowing who and where the young and infirm are, and mobilizing resources to get everyone to safety. Distant tsunamis, which are generated far enough away that we can't feel the earthquake associated with their formation, can still be powerful enough to cause damage. For the purposes of planning for inundation, no distinction is drawn between local and distant tsunamis. we have a set of warning systems in place that are worth looking into. Many centralized communities (i.e. Port Angeles, Lower Elwha, Neah Bay, La Push)have tsunami horns in place which are plenty loud to wake everyone up in the event of a tsunami warning. For homeowners who live away from those central areas, there are a series of alternate warning sources that would be put into service in the event of a tsunami warning covering our coast:

1) The Emergency Notification System. Homes can be directly called over their landlines and notified of emergencies of any kind. This system works only with landlines.

2) As of approximately spring 2013, Clallam County will add a new system that individuals can enroll in, which will route an emergency call to any phone (including cell phones/work phones, etc.) entered into the system.

3) Clallam County uses the alert system at to notify subscribers to any community-relevant alerts. A text is sent to your mobile phone...enrolling is free and easy (it took me about one minute).

4) And finally, the old stand-by...Clallam County Sheriff personnel, fire departments, or even the Coast Guard can all be used to directly canvas communities at risk. So, in the event of a tsunami warning, you could get a knock on your door from the sherriff...

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