The earthquake coverage over the weekend by CNN and MSNBC was appallingly bad. Utterly unscientific tabloid style journalism. Local coverage in LA was vastly superior. The networks could at least try to have geologists on call. Trump isn’t alone in being anti-science, apparently.
Tag Archives: Earthquakes
Liquefaction in the Heart of Screenland
Oh (he says to a seismically hypersensitive friend), you work in Culver City…. That explains how you felt an earthquake (technically a microquake) that measured 2.8 on the Richter scale. I try to notice nothing below 4.0, but then I am jaded. But Culver City is built on the Los Angeles River floodplain. In fact, the Ballona Creek that trickles unnoticed though the neighborhood was an alternate channel for the L.A. river in its carefree, unchanneled days. And the soil there must be many feet deep, sediments that go who knows how far back, and are more sandy than clay, given the source (the Santa Monica Mountains). What this means for your nerves is that sandy alluvial soils are prone to liquefaction, and amplify the slightest of earthquakes, so that something beneath of dignity of an Angeleno sitting on bedrock, as in my neighborhood, is noticed by highly sensitive types in Culver City. Were it a more manly earthquake, something, say, in the vicinity of an 8 plus, the earth beneath you would be as water and you’d never be heard from again, and Amoeba could at last have what remains of your record collection.
Here’s a link to a convenient map of the Culver City liquifaction zones. They’re in teal. This map is available on Culver City’s official website, though I doubt they tell anyone, since there’s more teal than is tasteful. Teal is best in small quantities. It’s a pungent off-blue and a little goes a long way, like a rank cheese. Also it makes Culver City look so screwed. Like beyond screwed. Like doomed. Which it’s not, really. It’s that damn teal. Pastels would have been much better.
Incidentally, Culver City is the Heart of Screenland.
Earthquakes in the grand scheme of things
“Scientists Fear the BIG ONE is Coming as FOUR Major Earthquakes Strike in 48 Hours” exclaimed The Express in proper tabloid fashion. Japan is rocked by four quakes in two days, each over 6 on the Richter scale. Not a terrible quake, a 6.0 or so, but a rocker and scary enough. There were even a couple deaths. Japan handles temblors like this well. They are used to them. Of course seismologists worry that they might be foreshocks announcing a real monster of a quake, though Japan is used to those too. Alas, there is nothing unusual at all about earthquake clusters like the four The Express is screaming about, especially in Japan, where four tectonic plates–the vast North American, Eurasian, and Pacific plates, and the smaller Philippine plate–grind against each other with slow violence. The northern half of Japan is mostly part of the North American plate, the Southern half is the Eurasian plate, and the Pacific plate is forcing itself beneath the Eurasian plate (a process called subduction) at a rate of about three and a half inches a year. Sometimes the subduction process gets stuck for a few years and then, after enough pressure builds up, it moves forward with a jolt. Sometimes it’s a little jolt. Sometimes it’s a 6 point jolt. And sometimes it’s a jolt so big everything shakes to pieces and the sea comes roaring back in a tsunami. That’s Japan. We have earthquakes in California as well, of course, but no one is subducting anybody. Rather our plates are slowly grinding past one another, so that the shaking, even at its worse, cannot get to the same level as Japan is prone to. In Alaska, though, where the Pacific plate is being subducted by the North American plate, you can have earthquakes of astonishing violence, like the one that leveled Anchorage in 1964.
The Express story hinted that the quakes in Japan could set off quakes in, say, California. As if somehow earthquakes were all interconnected. And while earthquakes on the same (or on linked) fault lines can be related theoretically, ones thousands of miles away can’t possibly be, because there would not be enough energy released from an initial quake to go through thousands of miles of solid rock from Japan to California. And the fact that there are four major quakes in 48 hours in a general region–say across East Asia–is just chance, as there are hundreds of quakes 6+ every year and sometimes a few of them happen within a couple day stretch.
Remember that earthquakes, in the grand tectonic plate scheme of things, are extremely minor events, just little quivers, nothing. While to us they can be terrifying, devastating, even catastrophic, in geologic terms they are just everyday things. After all, every great mountain range in the world is the result of literally millions of earthquakes. When you think how few large earthquakes you have lived through living in, say, Los Angeles, you get an idea of the time scale in building mountains, and how we can play no role at all in that process whatsoever. Nothing alive can. Mountains rise and erode as if life never existed at all. Because in the grand scheme of things life means next to nothing, really. Life is just a process for making coal or limestone.
The earth beneath our feet
(This was a quick Facebook post and is a bit of a mess but I’ll leave it as is….)
In wonderfully telegraphic prose, a comrade posted “earthquake in japan now. pacific rim is heating up. cali needs to be ready?”
A ha. Rocks. Earthquakes. The very earth beneath our feet. After myself, my other favorite subject. I actually decided against a career in geology for a career in punk rock, epilepsy and writing about me. Say a’a, the doctor said, and out flowed this:
About 90% (I began) of the world’s earthquakes happen in the Pacific Rim’s Ring of Fire, so it’s shaking all the time. There’s no connection between California and Japanese quakes, though. Our quakes happen because the eastern spreading portion of the Pacific plate (and a smaller connected plate) are being pulled under the North American plate, while Japanese quakes happen because Japan sits where the western spreading portion of the Pacific plate is being pulled under the plate that eastern Siberia is on. The fault zones are unconnected.
In California the plates are sort of moving past one another, the Pacific plate sliding beneath the North American plate at an angle, while in Japan the plates together slam head on. Subduction is not a pretty process. Geology, mostly, is violence in slow motion, a few inches a year. Those undulating layers you see in California road cuts are layers once horizontal subjected to immense pressures. The bend slowly. Sometimes, though, you see layers shattered, as if they exploded. That’s because often they did. You might be looking at the frozen remains of earthquakes. Rock busts into fragments and the surface above shakes. Sometimes a little. Sometimes a lot. The San Andreas Fault is where two tectonic plates slide past each other at about an inch and a half per year. Sometimes they catch and remain stuck till enough pressure builds up that they uncatch and destroy San Francisco. But there is vastly more energy to be released when plates collide directly than when they slide past each other, hence the frequency and power of Japanese quakes. Japan actually is the result of two (or is it three, I can’t remember) plates being dragged under (or subducted) beneath two other much larger plates. In Japan you have these two or three separate collisions (not just the one I alluded to in an earlier paragraph, keeping things simple), and each collision is vast and inexorable, and all that friction and compression and crunching and pushing causes nearly incessant earthquakes of sometimes unbelievable power and destructiveness. Indeed, Japan itself is a result of these collisions, with sea bed forced upward and vast amounts of the liquid rock mantle being released from cracks in the crust through volcanos. Geologically it’s a helluva mess, volatile and unstable and virtually quivering and literally quaking with pent up seismic energy. Just be thankful, Californians, that we have nothing even remotely similar to this. (They do in Alaska, which is how Anchorage was leveled in 1964, the Pacific Plate suddenly lurching violently and shoving itself beneath the North American Plate, leaving one side of the street thirty feet higher than the other.) The San Andreas may pop off every couple generations. Japan has giant quakes every couple years. They handle them with aplomb. Their buildings don’t fall down. Port au Prince Tokyo is not. It’s not even Fillmore.
As for the devastating Nepali quakes these past several days, those are the result of India slowly crashing into Asia for the past 50 million years. It’s weird to think that in that span of time there have probably been a million huge quakes in what is now the Himalayas, just like these last two. A million quakes raising the earth six inches each time is what created the Himalayas. The top of Mount Everest was at the bottom of a shallow sea a half billion years ago. The rocks way up there are full of fossil crinoids. Imagine how many earthquakes it took to raise them 30,000 feet into the air.
Next time you pass through a roadcut, take a look at the rocks exposed. The violence in those bent and twisted layers is incredible. So much power moving a couple millimeters a year. The earth moves in millions of years. We are nothing, our entire lifespan a geologic nanosecond, like we aren’t even here.
Still, I love rocks.
A roadcut on the I-40 outside Kingman AZ, with layers of sediments as horizontal as when they were deposited, now being split in two by a young fault. Come back in a few million years to see what it looks like.
Brick's Science 