The 1964 Alaskan Earthquake

Podcast Transcript

On March 27th, 1964, the second-greatest earthquake in recorded history struck the state of Alaska.

It was an absolute monster of an earthquake, completely devastating communities, including Alaska’s capital, Anchorage.

The quake was so great that people could feel it 1,200 miles away in Seattle.

Despite its power, the secondary effects of the earthquake might have been even worse.

Learn more about the 1964 Alaskan Good Friday earthquake on this episode of Everything Everywhere Daily.

The 1964 Alaskan Earthquake registered 9.2 on the Richter scale.

I want to reiterate that. It was a 9.2 on the Richter scale.

Before I get into the details of the Alaskan earthquake, I want to do something I have yet to do on this podcast, which is to explain exactly how the Richter scale works because many people aren’t aware of exactly what the numbers mean.

The Richter is actually called the Richter Magnitude scale. The key word is “magnitude.”

The Richter scale is a logarithmic scale. What this means is that an earthquake that measures 6.0 isn’t twice as powerful as one that measures 3.0. It is actually 1,000 times more powerful.

The key is measuring orders of magnitude, which is basically measuring the number of digits.

To create an analogy, let’s make a logarithmic scale for money.

If you are a two on this scale, then you have $100 because 100 has two zeros.

If you are a four on the money scale, then you have $10,000. A six is one million dollars, and a nine is one billion dollars.

The Richter measures the amplitude of seismic waves generated by an earthquake. Every point on the Richter scale is a ten-fold increase in power.

The more powerful the earthquake, the fewer of them there are.

Earthquakes below 3 happen every day around the world, and they usually can’t be felt. There are millions of earthquakes below 3.0 every year.

From 4 to 4.9, you will feel it if you live in the area, but there probably won’t be much, if any, damage. I’ve felt a few of these around the world. Earthquakes in this range can be measured by seismographs around the world.

From 5 to 5.9, it could damage poorly built buildings, but it probably won’t damage modern buildings. Things might fall off of shelves. There are 1,000 to 1,500 of these types of earthquakes per year.

From 6 to 6.9, it can cause severe damage to poorly constructed buildings near the epicenter and moderate damage to well-built buildings. The 1989 San Francisco earthquake was a 6.9. There are 100 to 150 of these per year.

From 7 to 7.9, we are in the realm of serious earthquakes. Depending on the construction quality, entire buildings can be destroyed, and even well-built buildings may suffer serious damage. The February 2023 earthquake in Turkey and Syria measured 7.8. The San Francisco earthquake of 1906 was 7.9.

Current California building codes, which are some of the best in the world, only require a building be able to withstand an earthquake up to 7.0

There are only 10 to 20 such earthquakes per year.

From 8 to 8.9, we are talking about very major earthquakes. These are truly devastating and also very rare. There might be one of these per year, and usually in an uninhabited area.

Whenever these strike a populated area, you can expect widespread damage.

Since seismologists have been measuring earthquakes beginning in the early 20th century, there have only been five which have been measured at 9.0 or great.

A 9.0 earthquake is so great, and it doesn’t really matter where it takes place. It’s going to do damage to something, somewhere, somehow. An earthquake above 9.0 will pretty much destroy everything.

The 2011 earthquake in Japan that wrecked the Fukushima nuclear power plant measured 9.0.

The 2004 earthquake in the Indian Ocean that caused the devastating tsunami that killed almost a quarter million people was a 9.1

So when I say that the Alaskan earthquake was a 9.2, and the reason I took all this time explaining earthquake magnitudes is that 9.2 is a number that you have to respect.

The only earthquake ever measured which was greater was the 1960 earthquake in Valdivia, Chile, which measured 9.5. This is close to the largest possible earthquake that seismologists think could be created via normal plate tectonic activity.

So what happened in Alaska?

At 5:36 pm local time, on March 27, Good Friday, a megathrust occurred between two tectonic plates. A megathrust is the largest type of earthquake known, and they only occur in subduction zones. It is estimated that the fault moved 30 to 60 feet. An enormous amount for such a short time in geologic terms.

In a previous episode on volcanoes, I talked about the ring of fire. The ring of fire is a region of tectonic plate subduction around the Pacific Ocean.

Southern Alaska lies where the Pacific oceanic plate goes under the North American continental plate. This fault line is responsible for the entire Aleutian Island archipelago.

So this type of earthquake couldn’t occur along the San Andreas fault, which runs along the coast of California, as it is not a subduction zone.

The earthquake lasted for four minutes and thirty-eight seconds.

The epicenter of the earthquake was very close to shore, only 12.4 miles or 20.0 kilometers north of Prince William Sound. More importantly, it was only 78 miles or 126 kilometers east of Anchorage.

Those who experienced the earthquake found something which was out of the bible. Paved roads rose and fell as if they were a slinky. The ground literally opened up in places.

There were vertical displacements of land as large as 38 feet or 12 meters. That means in a spot that was previously flat, there might now have been a cliff.

The coastline of Alaska literally changed. Some sections rose, and some went underwater. One section moved fifty feet towards the coast.

Buildings collapsed everywhere. Gas, water, sewer, and electrical lines were all cut.

One of the most pronounced memories that people had was the sound. They claimed that the earth was ringing like a bell. They were actually hearing the grinding of the tectonic plates.

In some places, the ground moved so much that it liquified. Liquefaction occurs during strong earthquakes on soil that is very loose and has a lot of water.

Liquefaction is extremely dangerous. Imagine the ground turning into the equivalent of wet sand. Buildings can collapse, and cars can sink into the ground.

Much of what geologists know about soil liquefaction, in fact, came from the Alaskan earthquake.

The most devastating consequence of soil liquefaction was landslides. Anchorage was hit by several landslides. The Turnagain neighborhood had 75 homes lost in a landslide. Many other neighborhoods and most of downtown Anchorage were destroyed.

The magnitude of the earthquake was compounded by its length. At over four and a half minutes, it was an extremely long quake.

As bad as everything I just described was, that was not the worst part of the earthquake. The worst part was the tsunamis.

Valdez, Alaska, was built on sand and gravel and suffered severe soil liquefaction. Much of Valdez slumped into the Valdez Inlet. This land moving into the water caused a massive localized tsunami.

The massive wave in such a small area caused water to slosh around like in a bathtub. One wave reached a height of 220 feet or 67 meters as it washed up on the surrounding mountains.

I went kayaking once in Valdez, and I was astonished when our guide showed us just how high the water went up the mountain during the tsunami.

This was just one of as many as 20 tsunamis that were caused by the earthquake. There were other localized tsunamis like this one which was caused by landslides.

However, there was also one big tsunami that was caused by the thrust of the tectonic plate itself.

The coastal towns of Seward and Kodiac were all hit hard. The small village of Chenega lost a third of its population and every building, save the school, which was located 100 feet above sea level.

The main tsunami swept down the western coast of North America. Large scale damage was reported in British Columbia, Washington, Oregon, and California. Four people were killed in Oregon by the tsunami and twelve in Cresent City, California.

The tsunami waves were reported as far away as Peru, New Zealand, Japan, and Antarctica.

The final death count from the earthquake was only 131, which was shockingly low for an earthquake of this size. The low number was mostly due to the fact that it occurred on a holiday in a part of the world with a very low population density.

Nine people died directly from the earthquake, and 122 died globally from the tsunamis.

While the population in the area wasn’t great, it was the most populated part of Alaska. Most of the communities in the region, which I mentioned, were totaled.

The town of Valdez had to relocate to higher ground. In addition to most of it just sliding into the sea, the oil storage tanks in the town ruptured, causing a massive fire.

You won’t find a lot of old buildings in Anchorage or Seward because of the earthquake. Almost all of the infrastructure had to be rebuilt from scratch.

For weeks after the earthquake, there were aftershocks that plagued the region. On the first day after the earthquake alone, there were eleven aftershocks that measured over 6.0 on the Richter scale.

One of the only means of communication after the quake was radio reporter Genie Chance of station KENI. She stayed on the air for 24 hours to help coordinate rescue efforts, guild people to emergency shelters, and help survivors find family members.

One of the things which came out of the earthquake was a much better understanding of how exactly earthquakes work. For the first time, the phenomenon of soil liquefaction was able to be studied closely.

The seismic data from the earthquake also proved the existence of subducting tectonic plates.

In the aftermath of the earthquake, the United States founded the National Tsunami Warning Center, which is headquartered in Palmer, Alaska. The tsunami warning center can now issue tsunami warnings in a matter of minutes, which can save lives all over the world.

Likewise, better building codes and locations of relocated buildings and villages improved safety for the day if and when such an event happens again.

Earthquakes of the magnitude of the 1964 Alaskan earthquake are extremely rare. It is entirely possible that many of us will never see an earthquake of this strength again. However, it is possible that one could happen this year.

If and when the next one does occur, the impact of it will be mitigated due to the lessons learned in Alaska in 1964.

The Executive Producer of Everything Everywhere Daily is Charles Daniel.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener Darrin who sent me an email. He writes:

Everything Everywhere Daily is a super fantastic podcast! Always interesting, educational, and horizon-broadening, I discovered it during the pandemic and binge-listened until I’d caught up to every episode.

Consistently enlightening and frequently ingenious, the Rock and Roll episode was no exception and had perhaps the best sly ending yet!

Without a time-bending feedback loop and the future (wait… is it past?) invention of the Flux Capacitor, we wouldn’t have Rock and Roll.

Well played.

Thanks, Darrin! Actually, you can find a working flux capacitor in the completionist club. If you should run across it, however, don’t touch the settings. We have dialed in precisely to 1.21 giggawatts.

Remember, if you leave a review or send me a boostagram, you too can have it read on the show,