Seaside Tsunami Information

Seaside Sirens - what do they mean?

Continuous Siren Blast: This is warning that a TSUNAMI MAY BE APPROACHING. If you did not feel an earthquake, then it is likely that the danger is from a Distant Tsunami (see below) that may be hours away. Everyone within the tsunami innundation zone (download map) should calmly and immediately evacuate to high ground, far away from the ocean.

Siren Blast that Rises & Falls: Around 7:30pm every Wednesday evening a siren sounds throughout Seaside. This siren is for the volunteer fire department, and does NOT mean that a tsunami is approaching. This siren can be distinguished from the tsunami warning siren because the pitch rises and falls (as opposed to the long continuous blast that serves as the tsunami warning).

Two probable but very different scenarios for a Seaside tsunami

SCENARIO 1:  A LOCAL TSUNAMI caused by a massive earthquake

Sometime between today and the next several hundred years, a massive (8-9 magnitude) earthquake will occur along the Cascadia Subduction Zone, less than 100 miles offshore.  The earthquake will last several minutes and literally knock people to the ground.  The serious, damaging effects of the earthquake will be felt as far as Portland and Seattle. But the shaking will barely have stopped before the next disaster arrives.  In as little as 15-20 minutes the first in a series of enormous waves will plow through coastal towns all along the Pacific Northwest.

What to do: The instant the ground stops shaking, you must run to high ground, far away from the ocean.  There will be no time for official warning.  In South Seaside, people can find safety by following the road up Tillamook Head.  People elsewhere in Seaside will need to find safety in the hills East of town (this involves crossing the Necanicum River, Neawanna Creek, and Highway 101/Roosevelt Blvd).  Take a look at the evacuation map and study possible routes, paying special attention to the bridges.  Although bridges are a dangerous place to be when the tsunami hits, and they might be damaged during the earthquake, you will probably need to cross a couple to get to safety.  For those who find themselves close to the shore or in the downtown area when the earthquake hits and/or are physically unable to run to the East hills, it is suggested that they find shelter on the 3rd level of the Trendwest parking garage, or the top level of the main Trendwest building located by the Turnaround.  Everyone will need to remain at their evacuation sites until an official “all-clear” is given.  Remember, tsunamis are a series of waves, and the first wave isn’t always the biggest.  Large waves will probably pound the shore for several hours.

SCENARIO 2: A DISTANT TSUNAMI caused by an earthquake far away

A distant tsunami could be caused by several different factors, but the most likely is an earthquake occurring far away, probably thousands of miles from Oregon.  The tsunami generated by such an earthquake would be smaller and would take much longer to reach the Oregon coast than in the Local Tsunami scenario.  There will be time for an official warning to be given via NOAA radio, TV and other media, and the siren in Seaside will sound as one continuous blast.  It will take several hours from the time the earthquake occurs before any tsunami waves impact the coast.  In the event that you are on or near the beach and do not hear the siren or the evacuation warning, your only warning might be the ocean pulling out unusually far from land.  (Before a tsunami hits, coastal water is pulled out far to sea, while the water mass generated by the earthquake piles up behind it, higher and higher, creating the  massive tsunami wave).  If at any time you see the ocean suddenly “disappear” out to sea, take this as a warning of an approaching tsunami and evacuate immediately.

What to do: The evacuation procedure for a distant tsunami is the same as for a local tsunami. People should immediately get to high ground, away from the ocean and assemble in areas outside the inundation/hazard zone (see map).  The difference is, you will have more time to gather your family and make it to safety - a matter of hours rather than a handful of minutes.  Keep in mind that vehicle traffic will be extremely slow moving and congested.  It is still a better idea to evacuate on foot if at all possible.

Summary of possible tsunami warning signs

The following is a list of possible indicators of an approaching tsunami:

• Earthquake / Ground shaking
• Tide suddenly and unexpectedly pulls far out to sea (would significantly drain the Necanicum River too)
• Siren sounds in Seaside as one continuous blast
• TV, Radio or Web bulletin reports that a tsunami warning has been issued for Seaside
• NOAA radio alert (NOAA weather radios can be purchased online and at electronics stores)
• Emergency officials tell you to evacuate
• Birds & other wildlife behaving abnormally or fleeing (many animals such as pidgeons can hear the ultra low frequency sound waves or "infrasound" created by large waves and earthquakes from many miles away)
• A roar like an jet airplane or train may be heard as tsunami waves approach

ALWAYS EVACUATE IMMEDIATELY if you feel an EARTHQUAKE, hear a CONTINUOUS SIREN BLAST, or learn a TSUNAMI WARNING ALERT has been issued for the area. ALWAYS EVACUATE IMMEDIATELY if you see a SUDDEN DRASTIC DROP IN SEA LEVEL, even if you don't hear a siren or official warning. If you are unsure/unfamiliar with normal Seaside tides, ask someone or try to find out if an official warning has been issued. The water level often drops shortly before a tsunami comes ashore, so time is critical. If you see a "wall of water" on the horizon, or hear the roar of an approaching tsunami, you will need to run as quickly as possible inland to higher ground (probably to a tall building). Other warning signs should not be ignored. There are generally some warning signs that a tsunami is approaching, but we must be observant and either evacuate immediately or actively seek more information.

Being Prepared

Knowledge is the first step in being prepared. Review the tsunami warning signs, scenarios, and what to do in the event of a tsunami (see above). You should also print out the Seaside Tsunami Evacuation Map and study the innundation danger zones. You might be surprised to see what areas are dangerous and how far you will need to travel to get to safety. Pay careful attention to where the bridges are since you will need to use them to cross the two rivers that run through Seaside in order to get out of the hazard zone. Think about what you would do differently if you needed to evacuate from different areas of Seaside. Make sure all members of your family, including children, are acquainted with this information. Though the idea of a tsunami is upsetting to many people, the best remedy is not dismissing the idea, but rather learning more. Knowing what to look for and what to do will go a long way in easing your mind. Remember, you will likely have several hours to evacuate before a distant tsunami arrives. And in the case of a local tsunami, the course of action is simple: immediately run inland to high ground. Keep in mind that the scenario that results in a local tsunami will not be much better elsewhere in the Pacific Northwest. The earthquake that could cause such a tsunami on the coast will also cause massive amounts of damage and other dangers in the larger cities.

Seaside Tsunami Evacuation Map (PDF)

City of Seaside Tsunami Info & Preparedness (visit this site for more preparedness info!)

NOAA Pacific Tsunami Warning Center - Bulletins