Copyright © USGS
Copyright © 2025
by Ralph Couey
Like most earthquakes, this one struck suddenly off the Kamchatka Peninsula, on the far eastern edge of Russia. An initial assessment of magnitude 8.0 was quickly upgraded to magnitude 8.8, the most powerful earthquake in 14 years.
As most people know, the Earth's surface is made up of numerous interlocking plates that float on top of the convection currents of the hot mantle beneath. We also know that throughout Earth's history, these plates have been in constant motion, sometimes forming supercontinents. Other times, they float away from each other. In this case, the Pacific Ocean Plate subducts or slides beneath the Okhotsk Plate. Also, in most cases, this motion is not smooth. The plates will, on occasion, stick together. But the oceanic plate still maintains its drift, which builds up pressure at the "stuck point" that scientists call the asperity. As this happens, the continental plate rises and folds, just like curling your fingers into a fist. When the elasticity of those rocks exceeds their frictional coefficient, they snap past each other. When that happens, the continental plate snaps forward and up (unclench your fist quickly). Since this occurs on the floor of the ocean, the snapped plate lifts a column of water as deep as the ocean at that point and as wide or long as the fault. In this case, that depth is roughly 2.5 to 3.5 miles deep. Plus, the quake originates deeper, also in this case, about 11 miles beneath the ocean floor. This column of water was (strike the average here) 3 miles tall and 350 miles long. When that column breaks the surface, gravity tears it down into a series, or train of tsunami waves, calving off in opposite directions. One towards land, and one that launches across the Pacific Ocean.
Subduction zones are monsters. They have historically generated the most violent earthquakes and most destructive tsunamis in history. Chile 1960, Alaska 1964, Tohoku 2011, and Indonesia 2004 all originated from these types of faults.
Pacific Tsunami Warning Center, located on Ford Island in the middle of Pearl Harbor, Hawai'i, is the agency tasked with analyzing earthquakes and tsunamis and determining their threat to public safety. The initial assessment of 8.0 is sufficient to issue a Tsunami Watch. But with the later evaluation of 8.8, a Tsunami Warning was issued. Hawai'i Emergency Management Agency's State Warning Point immediately issued the required alerts, one of which was the Wireless Emergency Alert, or WEA, that exploded on everyone's cell phones.
These waves are detected and tracked via a system of what are called DART buoys (Deep Ocean Assessment and Reporting of Tsunamis). There are two parts of these sensors. Floating on the surface is a satellite transceiver. A cable drops down to the ocean floor, where it is connected to a sea floor sensor. When a tsunami moves, like I mentioned, it is an entire column of water, miles tall. When the wave passes the sensor, it detects the weight of the column of water. A signal is sent to the floating buoy and then fired off to the satellite. Within a few seconds, the entire scientific world knows what has happened. These buoys, 39 of them so far, are set up along the seaward side of known subduction zones, and off islands along the possible wave routes. One of the limitations is that if the wave is generated landward of that buoy line, the wave that impacts the nearby land will get there before the buoys detect it. But most of the millions of people who live along subduction zones have learned that when the earth shakes, they need to move inland, or uphill.
The first indication was the appearance of tsunami waves in Russia and Japan. Japan saw waves about 3 feet in height, while the areas of Russia immediately adjacent to the event saw wave heights ranging from 10 to 16 feet. As the waves moved eastward, Guam and Wake Islands reported waves ranging up to 6 feet. Midway Island, part of the Hawai'ian island chain, also reported 6-foot waves. The forecast for Hawai'i, based on these results, was for waves in the range of 3 to 10 feet along the north- and west-facing shores. Evacuations were ordered, and the entire state collectively held its breath.
When the tsunami arrived, it numbered around 20 separate waves, eventually ranging from 3 to 7 feet. Thankfully, there was some minor flooding, but no damage was reported, and even more importantly, no deaths or injuries.
The first big question was why the waves were not bigger. The answer lies in the amount of slip at the earthquake origin. Estimates today estimate that the sea floor rose 10 to 20 feet over a distance of 430 miles. This is significant. But the Indonesian quake in 2004 generated an uplift of around 50 feet along a distance of 745 miles. This difference accounts for the smaller waves. But there is speculation among scientists that this fault may not be done. The entire Kuril-Kamchatka fault runs over 1,300 miles end to end, and may yet rupture along the rest of its length, perhaps in pieces, or a full-margin rupture.
I was at work aboard the Battleship Missouri Memorial in Pearl Harbor, and since I'm not allowed to have my cellphone with me while I'm working, I missed the initial alerts. On a break, I checked my phone just in time to see the Tsunami Warning WEA message. We continued on as usual because the wave arrival time was three hours after we closed. But as more messages came in, it was decided to allow those who lived in the immediate danger zones, North Shore and the Waianae Coast, to leave early. I stayed until I was ordered to leave, reluctantly. Even the security staff was sent home, and for a rare night, the ship was left utterly vacant.
The trip home was a nightmare. Everyone working on O'ahu was sent home at about the same time. The people who were in the evacuation zones were also trying to get inland and uphill. Also, the emergency services were attempting to deploy. A perfect storm. Traffic was gridlocked. The Army opened up the Kole Kole pass road to improve traffic flow. Officials today are admitting that they need to rethink this evacuation plan.
At any rate, it took me almost an hour and a half to get the 6.5 miles from work to home. But for the most part, people followed the advice relayed via radio stations to stay calm, be patient, and stay Aloha. There were some accidents, and I did see some tourists hoofing it inland as well.
Government officials were on the ball with the information flow. The only flub happened at 5 pm when the Mayor's and the Governor's separate news conferences went off at the same time as an updated alert was sent via the Emergency Alert System that went out over local television networks. So not much was heard from either office. Fortunately, the pressers were better coordinated as more data was issued from PTWC.
Mayor Blangiardi several times warned people to not get taken in by the numerous conspiracy theories and massively incorrect information that was being sent out via social media. He advised folks to ignore the socials and stick with authoritative sources from the government through the news media.
Once home, I turned on the local news stations and followed the event up through the arrival of the second and third waves. It was clear that while significant, it was not going to be the historic disaster it could have been. There will be those filled with their own warped sense of self-importance who will insist that the evacuations were unnecessary, as the waves really were not destructive here in Hawai'i. As it turned out, the initial forecasts of 3 to 10 feet were in line with the actual measurements of 3 to 7 feet, a monumental win for PTWC, given the distance from the earthquake source.
One important thing to be aware of here. Hawai'i is surrounded by subduction zones, excepting a narrow 30-degree arc facing due south. Any one of these faults is capable of producing a high magnitude quake, north of magnitude 8.8, and generating massive, destructive Pacific-wide tsunamis as they have done throughout Earth's long geologic history. From southeast and southwest Asia, up the coasts of the Philippines, Japan, Korea, and Russia, across the vast Aleutian arc to the Queen Charlotte fault system. Starting at British Columbia and stretching south 700 miles to Cape Mendocino, California, is the ominously silent Cascadia faultline. More thrust faults exist off Mexico, Central, and South America. The rupture of any one of these could spell disaster for tens of millions of people.
Earthquake prediction is not possible at this time. Linear events can be predicted, but what is going on beneath our feet is not linear, but chaotic, and thus unpredictable. The only thing we can do if we choose to live in these threatened areas is to be alert, informed, and ready to evacuate to safe areas immediately.
Again, this event could have been much worse. We need to be aware that the next one just might be catastrophically worse.
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