Wednesday, March 16, 2022

Time to Test for Tsunami Preparedness

Posted By on Wed, Mar 16, 2022 at 5:52 AM

click to enlarge Tsunami warning sign. - FILE
  • File
  • Tsunami warning sign.
In just the last few months, Mother Nature has sent out a few reminders about the North Coast's seismic vulnerability, including two earthquakes separated by seconds in December — a magnitude-5.7 and 6.2 — and the tsunami generated by a volcanic eruption near Tonga in January.

While Humboldt County was largely spared in both cases that doesn’t mean the region will be so lucky the next time, if the distant and not-so-distance past is any indication. To help residents be ready, local emergency officials have planned three Tsunami Preparedness Week events that will be taking place in the coming days.


“Humboldt County is prone to a variety of natural and human-caused disasters,” said Ryan Derby, the county’s Office of Emergency Services manager. “Your best tool to effectively respond to and recover from a disaster is your personal preparedness.”


At 9:30 a.m. Saturday, there will be a walking evacuation drill in Manila, with sheriff’s deputies and Arcata Fire Department trucks driving through neighborhoods sounding hi-lo evacuation sirens while the OES tests out the Zonehaven AWARE system, a new mapping tool for first responders that categorizes Humboldt County neighborhoods into specific zones to determine evacuations areas in the event of an emergency.


After hearing the hi-lo sirens, Manila residents are being encouraged to visit community.zonehaven.com to find their designated evacuation area on the map and proceed to higher ground.

The annual Tsunami Warning Communications Test takes place March 23, starting at 9 a.m., with OES testing the local warning system: Humboldt Alert. Residents who are signed up will receive notifications on their cellphone, landline, or email. That will be followed at 11 a.m. by the National Weather Service running a test of the Emergency Alert System, with alerts being sent out via radio and TV broadcasts, NOAA weather radio and reverse 911 calls. In some areas, tsunami sirens may be activated and people on the coast may hear test broadcasts from planes.

During last years's test, nearly half of the county's 12 sirens remained silent after being "corroded to oblivion" by years of exposure to salt air and the North Coast's notoriously wet weather. The Journal's March 10 cover story "Icons of Preparedness," looks at the cost vs. the benefit of replacing the sirens, as well as whether the devices are as effective as cellphone alerts and other warning systems, as local emergency officials weigh the options moving forward.

A final drill will take place March 24 in Shelter Cove, which runs its own siren system, with the three located in area being sounded. For more information, contact the Shelter Cove Fire Department.

“Recent events like the December 6.0M earthquake and January tsunami advisory really served as a wake-up call to some of our coastal communities regarding the very real threat of a destructive tsunami,” Derby said. “Whether you are on the coast or inland, now is the time to begin getting yourself and your family prepared for whatever disaster the future may have in store.”

But the warning systems being tested in the three preparedness events are most useful for a distant-source tsunami, like the one generated back in March of 2011 by a devastating earthquake off the coast of Japan, when Humboldt County was under the highest threat level, a tsunami warning, and the local sirens were last sounded as an alert. In that scenario, officials are likely to have hours to get out the word. (The sirens are not activated if the region is under a lower-level tsunami advisory, which was the case back in January.)

A far bigger threat lurks in our own backyard, a rupture along the Cascadia subduction zone, which could send surges beyond beaches and the harbor in minutes. Then, intense shaking will likely be the only warning. 


Nearly 30 years have passed since a small corner of the Cascadia subduction zone ruptured near Petrolia on April 26, 1992, shaking the region with such intensity that seismic sensors in the area were overwhelmed and a 15-mile section of coastline was thrust several feet into the air.


Within minutes, for the first time ever recorded on the West Coast, a locally generated tsunami arrived on shore, with a small wave arriving at the North Spit  less than a half-hour after the magnitude-7.2 earthquake struck just before 11 a.m.  Southern Humboldt beaches were hit even sooner.


In the quake’s aftermath, landslides shut down roads, water mains burst, windows shattered, a wide swath of the North Coast was left without power and fires destroyed the Petrolia post office and a shopping center near Scotia. Hundreds of people were injured and homes damaged.


But for all the ferocity released by the earth that day, the Cape Mendocino Earthquake was just a sampling of what the Casacadia subduction zone has the power of unleashing  — a magnitude-9.0 or greater megathrust quake, which last occurred in 1700. 


In that case, local emergency officials stress, the only warning will be the ones Mother Nature has to offer: prolonged, intense shaking, a loud ocean roar and the sudden receding of the water to show the sea floor. Any of which means time is of the essence and to head for higher ground immediately.

Read the OES release on Tsunami Preparedness Week below:

Do you know what to do in the event of a tsunami? Tsunami Preparedness Week is set for March 21-25, 2022, and the community is invited to take part in any of the several events happening this month to bolster your personal preparedness for a local tsunami.


Kicking off tsunami week, on Saturday, March 19, the community of Manila will undergo a walking evacuation drill beginning at 9:30 a.m. As part of this drill, Humboldt County Sheriff’s deputies will patrol several neighborhood streets sounding the Hi-Lo Evacuation Siren and Office of Emergency Services staff will conduct a test of Zonehaven AWARE, the county’s new evacuation mapping tool. Residents in Manila are encouraged to walk to higher ground, as designated in the included map, upon hearing the Hi-Lo siren. This drill is being organized by the National Weather Service in coordination with the California Governor’s Office of Emergency Services and the Manila Community Services District.


On Wednesday, March 23, a test of the Tsunami Warning Communications System will be conducted for Del Norte, Humboldt, and Mendocino counties. Beginning at about 9 a.m., the Humboldt County Sheriff’s Office of Emergency Services (OES) will conduct a test of Humboldt Alert, the county’s emergency alert system. Residents who are signed up for Humboldt Alert, will receive an alert to their cellphone, landline, or email as part of this test. Later that morning, at 11 a.m., the National Weather Service will then conduct a test of the Emergency Alert System (EAS). As part of this test, alerts will be sent out via radio and TV broadcasts, weather radio, reverse 911, and tsunami sirens may be activated in some areas. People on the coast may also hear test broadcasts from airplanes.


Finally, on Thursday, March 24, the town of Shelter Cove will undergo a walking evacuation drill. During this drill, the town will also test their tsunami sirens. For more information about this drill, please contact the Shelter Cove Fire Department.


“Humboldt County is prone to a variety of natural and human caused disasters,” said Ryan Derby Humboldt County Sheriff’s OES Manager. “Your best tool to effectively respond to and recover from a disaster is your personal preparedness.”


Humboldt County residents are encouraged to utilize Tsunami Preparedness Week to review your personal preparedness plans for a local disaster. Find out if you live, work, or recreate in a Tsunami Hazard Zone and create a plan for how you will respond should a tsunami occur. Create and discuss your emergency plan with family, friends and co-workers.


Residents are also encouraged to sign up for Humboldt Alert, the county’s opt-in emergency alert system, and to find their pre-designated evacuation zone using Zonehaven AWARE, the county’s new evacuation mapping tool. Remember, we can’t alert you if we can’t reach you.


“Recent events like the December 6.0M earthquake and January tsunami advisory really served as a wakeup call to some of our coastal communities regarding the very real threat of a destructive tsunami,” Derby said. “Whether you are on the coast or inland, now is the time to begin getting yourself and your family prepared for whatever disaster the future may have in store.”


Find out more about preparing for earthquakes, tsunamis or any other disasters on the North Coast at https://rctwg.humboldt.edu or Ready.gov.   

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Kimberly Wear

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Kimberly Wear is the assistant editor of the North Coast Journal.

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