Seismic shift: How the Great Alaska Earthquake of 1964 changed science

[Blue_In_AK]

It's a big week for "celebrations" in Alaska - the 25th anniversary of the EXXON VALDEZ spill and the 50th anniversary of the Good Friday earthquake. This is an interesting article about how study of the earthquake helped prove the theory of plate tectonics.


http://www.adn.com/2014/03/23/3389995/seismic-shift-how-the-good-friday.html?sp=/99/100/&ihp=1

The Earth's crust consists of massive slabs of rock called plates. The two largest, the Pacific Plate and North American Plate, make up more than a third of the world's surface. They meet in a border that stretches from Baja California to Japan, and arches across the Gulf of Alaska. Two hundred miles southeast of Anchorage, the Pacific Ocean floor grinds into the North America continent at a rate of 2.3 inches a year, a nearly irresistible force meeting an almost immovable object. The two plates are locked at their line of contact and the lighter North American formation bulges upward.

At 5:36 p.m. on March 27, 1964, pressure overcame friction. Pacific Plate dove under the North American Plate, curling downward like a conveyor belt. Centuries of accumulated compression released violently and the coast of Alaska sprang forward as much as 64 feet.

The Great Alaska Earthquake released more energy than all other North American quakes since. Its magnitude, 9.2, made it the second most powerful earthquake ever recorded.

As shockwaves spread to the mainland of Southcentral Alaska, birch trees whipped back and forth, their tops touching the ground. Bridges gave way, roads split in half, rails twisted, power lines snapped. Buildings swayed and collapsed or slid into rubble as the weakened ground beneath them turned into mush.

Under the ocean, massive landslides displaced incalculable tons of water, sending waves as high as 200 feet into the coast. More waves generated by the rupture itself followed, racing to shores thousands of miles away. Water in wells on the other side of the globe oscillated up and down. In the words of Peter Haeussler, U.S. Geological Survey research geologist, the whole world jiggled "like a giant water balloon."

<snip>

Something else also shifted that day. Science.

<snip>

[adirondacker]

1. Excellent article! I look forward to making a trip up there one day soon.

Have you read "The Map That Changed The World" by Simon Winchester? Fun, and one of my favorite geology reads.

http://www.amazon.com/The-Map-That-Changed-World/dp/0061767905

[Blue_In_AK]

2. I haven't read that.

Thanks for the recommendation. I love science.

[adirondacker]

3. You're Welcome!

He's got several other books as well. Another author that is great is John McPhee if you are a rock jock or fascinated with geology.

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=John+McPhee

[truedelphi]

4. But there are many things about the earthquakes we witness that we still don't understand.

What effect does the magnetics inside and around our planet contribute?

How does the earth decide which place to hit?

Animals and some people know before an earthquake hits, but our instruments lag behind. (And why and how does mammalian life "know" - is it the radon gas released before the quake, or some other phenomena?)

I get "earthquake arthritis," and I look to my cats to see if it is something that will hit locally (I live in an area known for its thermal geyser earthquake activity,usually anywhere between 2.1 and 4.1.)

[Blue_In_AK]

5. I was in a earthquake in San Francisco in 1969 or 1970

and I remember my cats going absolutely nuts right before it struck. My first thought was, "how in the world did these cats make the whole building shake?" LOL. Obviously, I was an earthquake neophyte.

Now, living in Alaska, I hardly feel them unless they're over 5.0.

[Scuba]

6. Excellent read, thank you for posting. Looking forward to tomorrow's coverage of the tsunami.

[Blue_In_AK]

7. Here's a link to the first article in this series,

a little more personal...

http://www.adn.com/2014/03/22/3388654/march-27-1964-the-day-the-world.html

[Scuba]

9. Cool, thanks.

[truedelphi]

10. The story of the two families really affected me.

A vivid reminder of how life can change all in one quick moment.

Thanks for posting this.

The worst earthquake I experienced was the Morgan Hill/Silicon Valley earthquake, where I was working for Intel. We had been told to stay calm in an earthquake. Our orders from management had been that in the event of a quake, to go under our desks.

My co worker was under her desk; I was under mine. I am sure our bodies were trembling every bit as much as the earth. She yelled, "The air conditioning unit above our heads weighs six thousand pounds."

And the second she said that, we both decided to run. Then Shockley came out of his office to view us workers standing dazed in the parking lot. This was only a few short minutes later, and he took to scolding all of us. (Nobel prize winning scientist Shockley.)

He said, "After a big rumble like that, it's over. You should go back to your desks and work."

Apparently he wasn't as big on geology as he was on electronics, and he had never considered aftershocks.

Still, we workers were in such a state of shock that we went back in and sat at our desks. Since 90% of what my dept did was by phones, and the phones were out, we all sat there, chattering to each other in a crazed way, until it was time to go home.

I moved out of Silicon Valley area less than six months later. Marin County was much safer, if you didn't live in Larkspur or Corte Madera. (Those areas close to the Bay are gonna be all jellified if and when the Big One hits.)

[Blue_In_AK]

11. Jelly is exactly what happens here,

especially over by the Inlet. Even with Earthquake Park right next door, the very wealthy have built big mansions over there simply for the view (which is inarguably gorgeous). Every time I walk past them on the Coastal Trail, I think about what unstable ground they are on.

[SheilaT]

8. Another excellent book on earthquakes

is On Shaky Ground by John Nance. It has something like five chapters on the Good Friday quake, as well as an excellent discussion of how that quake shaped seismology. It's also somewhat important that the even stronger earthquake in Chile in May of 1960 made seismologists and geologists really begin to think that plate tectonics was the correct description of how the earth moved, and the Good Friday quake absolutely confirmed it.

[Enthusiast]

12. K&R! Fantastic article, Blue_In_AK!