How Earthquakes Work

What makes the earth quake? Join Josh and Chuck as they explore the science and history of earthquakes in this podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
Brought to you by the reinvented two thousand twelve camera.
It's ready. Are you welcome to Stuff you should know
from house Stuff Works dot Com. Hey, and welcome to
the podcast. I'm Josh Clark. With me is Charles W.
Chuck Chuckers. I love you, Bryant, you're saying that or

(00:24):
that's my middle name. I love everybody. Sure, I'm in
high spirit city, Chuck. Things are moving, stuff is taking place,
things are coming to. Fruition is out of nowhere because
you were not feeling this way, like literally seconds before
we recorded. I don't know what you're talking about. Wow,
I'm in brass, dude. You can turn it on. You
know why, Chuck? Why? I can tell because you're drinking

(00:45):
your little energy drinking. Yes, I would call it an
energy soda, be little dream sailor. That was Yeah, you
really like that podcast? Into it? I thought it was good.
My favorite part was when we mentioned the doctor in Berkeley,
when you said, um boom or around or something like that. Yeah,
that's funny. Yeah, thanks, I thought um. I liked all

(01:05):
the nose breathing I did in that podcast. For some reason,
we just sit around talk about our whole podcast Hey, Chuck, Hey, Josh,
you did some time out in l A right. Yeah. So, um,
I know that you met Matthew McConaughey. You left that
story and uh keep for Sutherland's driver. Yeah, and him.
I saw him in the grocery store too, with his driver,

(01:27):
No with How did you know it was him that
a bucks? Some blonde babe actually got you? Um it
was Keith for Southernlandon. I mean it's unmistakable got you.
Um he's breathing, mouth breathing behind me in line. We're
gonna get in trouble one day for that. I know
he's a hot head too. He just got suited. He
like hit a photographer somebody did he really? Yeah? So
watch watch your back. Plus he knows his way around

(01:49):
a gun, Yes he does, and he's ruthless, as I
understand it from what I've seen on TV. I know
what you're about to ask me about Los Angeles. I
know you do, because we're doing how earthquakes work. So Chuck,
let's just cut to the chase, shall we. I have
never felt an earthquake out there, nor have I. I
was out there for four years, dude, and I was
there when earthquakes happened, and I never realized it and
felt anything. Friends of mine will be like, dude, did

(02:11):
you feel that this morning? Yeah? No, I have no idea.
Did they use a lot of that um honey that
comes in the Little Bear? Yes? Did they? They did, dude,
that's what they say. And Kelly Chuck, I've never experienced
an earthquake either. The closest um thing to an earthquake

(02:32):
story I have involves earthquake proofing. Let's hear it. Remember
my friend Hippie Rob, Hippy Rob did a little time
out in Uh, I'm so a fan of the honey Bear. Yeah, yes,
oh yeah, Hippy Rob did a some time out in
San Quentin. Actually really yeah, here's the thing. He was
not looking forward to doing San Quentin, I imagine, um.

(02:53):
And he finds out that right when he gets there
that um, he and all the other relatively light off
enders are going to be moved to Fulsome prison, which
was undergoing earthquake proofing construction. Right, so they were going
to keep all the light offenders at Folsome and then
move all the light offenders at San Quentin over to Folsom.

(03:14):
And then they moved all like the murderers and rapists
and peder asks to uh that we're at San Quentin.
Fo over to San Quentin. Wow, that's my earthquake story.
Good for Falsome. So Hippie Rob got off easy. He
was with light offenders in Falsome? Did he Did they
actually have to work on the earthquake proofing where they
put the work or was it just go? I don't

(03:35):
think so. Would you trust the guy named Hippie Rob
to earthquake proofs your prison? Would not? I wouldn't either.
So let's talk about earthquakes. Let's do it. Can I
you want a little history? I did some extra research.
Let's hear it. So before nineteen fifteen, we didn't really
have much of a conception of what was going on
geologically with with the continents, right? Was it just anyone's

(03:57):
gas at that point? Yeah? I think you or I
could have come up with adequate theory. We'd be like
ghosts or something like that. Um, but the ghosts was
not an acceptable explanation for a guy named Alfred Wegner. Uh,
he's a German clearly because his last name because with
a W, but I pronounced it with a V, which
is a dead giveaway for a German is a German,

(04:18):
right um. So Wagner Um was actually an astronomer by training,
but he was fascinated with geology, and he became increasingly
fascinated when he found out that there had been fossils
identical plant in animal fossils found um on the let's see,
that would be the east coast of South America and

(04:39):
the west coast of Africa. And at the time, the
predominant theory was that there were land bridges that were
now under water and that's how these species would have
gotten together. Wegner he thought, I don't know that that's
entirely true, and he also noted that Africa kind of
looked like it could fit into South America. Interesting point.
So he started thinking about it and think about and

(05:00):
he realized that some he he postulated about three million
years ago, all of the continents were hooked together, which
he called one big, stinking massive land right in Greek,
that would be Pangaea. And uh so Pangea starts to
break apart, and basically Wevegner uh postulated that the the

(05:23):
continents were in fact still drifting. He thought that they
were basically plowing along the ocean, and it was due
to centrifugal force and title movement. And title movement, it
makes sense for the time. It's back in UM. He
was right about the continents drifting. We know that, but
not with the centrifugal force the title movement. One of

(05:45):
his rivals calculated that UM, for the tides to move
a continent, that that kind of force would actually stop
the rotation of the Earth in less than twelve months.
So that wasn't it. But he was right about the
continents drifting. UM. He was pretty much ridiculed during his lifetime.
But in the nineteen fifties and sixties, as we got
more and more acquainted with UM, the the actual ridges

(06:09):
along the plates, uh, they figured out that Vegner had
been right. The continents were in fact drifting, not in
the way he thought. Right, go, go Vegner, that's the
history lesson. That's good. And I didn't know that. I know,
I told you it was extra research. And that's continental
drift theory. Right. Once we figured this out that actually

(06:30):
the what is that the lithosphere, the surface of the
Earth which all these different plates make up, are actually
moving along the atheneos sphere, which is this layer of
rock that Actually it is a lubricantant behaves like a
liquid because of the heat and pressure, right, right, So
it's the goop in between the plates that's kind of
cushioning everything. Right. And we figured this out. I didn't,

(06:53):
You didn't, but you know, geologists did. Um and we
once we figured it out, we realized that that explains
all sorts of stuff like volcanoes, um, trenches, yes, mountains
under ocean, uh, bridges under the ocean. But most importantly
this podcast, it also explains Yeah, volcanoes, plate tectonics, earthquakes.

(07:15):
It's good stuff. Earthquakes, no volcanoes, Okay, tsunami. Well so wait,
we're gonna switch mid podcast and do how volcanoes work.
Let's just make it up. Yeah, it really does. It
explains earthquakes, uh, and it all makes sense. And I
love plate technico tectonics. Who doesn't, you know, just the
thought of our earth. I don't know. Stuff like this
makes me feel insignificant in a good way, that that

(07:38):
you know, we're kind of on this earth humans and
we think we're all that, but we're really pit the
whim of whatever the Earth decided to do. There was
something going on at the core that we didn't know
about right now, and all of a sudden everything started
going haywire. We'd be powerless. Oh yeah, so I kind
of like that insignificant feeling occasionally. I mean we're powerless
to you know, baseball size hail. Yeah exactly, you know,
let alone the movement of continents. Yeah, you want some stats, Josh, Chuck,

(08:03):
I knew you'd bring those up. There are actually many, many,
many earthquakes all the time. Uh, you just don't feel
them all. They don't get attention if you don't feel them,
and they don't get attention if they're not where people are,
which a lot of them are as well or away
from people. Uh, there's one earthquake every eleven seconds, Josh.
That's eight thousand per day, about three million per year. Actually,

(08:24):
the U S Geological Survey maintains the site Chuck um
that has like updated earthquake activity around the world. Did
you know about, let's see, six hours ago, there was
a six point seven earthquake UM in Papua New Guinea. Dude, Really,
that's big. It's a pretty cool sit Anything over seven
is the major scale is a big time major. Yeah,

(08:46):
we'll get to the Richter scale and if you don't
give it away. So, yeah, that many earthquakes is a lot,
but you don't feel them if they're if they're must
them are deep underground, right or in uninhabited areas exactly,
And so unless it's in a may your city or
something and killing folks, it's not gonna make the news.
But speaking of killing folks, have got one more stat
I like this one. One point five million people have

(09:08):
died from earthquake related activity in the last hundred years alone.
And you know, earthquakes get a really bad rap, chuck,
because really most of those debts are attributed to you know,
collapse structures or tsunamis or mud slides generated by the
earthquake exactly. The earthquake just opens up, the earth opens up,
and he swallowed into it like the movies, except in Superman.

(09:32):
Yeah remember that. Yeah, he reversed it. That dude flying
very fast, and he liked the Lex Luthor's girlfriend doing
so too. He did crickets, Josh, I think we should
get back to tectonics. Okay, let's talk about plates under
the earth and what can happen. Basically when these things

(09:55):
meet up. The two plates meet up, right, which where
they where two plates meet is of it's a fault, right, right.
You probably heard of the San Andrea's fault line in California,
very famous. Fault faults are where most earthquake earthquakes happen.
I keep on say volcanoes, it's so weird. So, uh,
what happens when plates get together is they can do
a couple of things. They can move apart from each other. Uh.

(10:17):
In that case, the magma comes out, Magma turns into
lava that cools and hardens, and then it kind of
reforms as part of the structure. So we should he
uses through and then makes it more solid, right, and
then it cools and you have a new land mass form.
Exactly right. We should also probably point out here to
any um people who believe in the hollow earth theory

(10:38):
that we're discussing this based on the notion that the
Earth's core is molten. Okay, yeah, sure, so go ahead
and chuck disclaimer there. What kind of fault was that
that you just described? Well, no, that wasn't a fault.
That's just what happens when the plates move apart. When
the plates pushed together one oftentimes one will go underneath
the other. Like they'll meet up and then one will

(10:58):
slide onto the other one and it dissolves basically at
that point. And the final thing josh Ish the plates
can slide against each other, so they just kind of
pass in the night, basically, just kind of moving by
each other very slowly. And all these different things that
I'm talking about where these plates meet, that is where
we get to the faults. Right there, there's four kinds, right,

(11:19):
the S and D. There's four kinds that can they
either go vertically or horizontally. As far as the faults
are concerned, You've got the normal fault and the reverse fault.
Those are vertical faults, right, So the normal fault is
where the plates actually move away from one another. The
reverse fault is where they moved together, right, And then
you have ones that that move horizontally, which I think

(11:40):
the San Andrea's fault is is a horizontal fault. Is
it a thrust fault? I think it's either a thrust
fall or strike slip fault. Okay, so it's basically the
same thing, except along along horizontal lines rather than vertical. Right,
But no matter which way they're moving, they can be
moving apart, moving together horizontally or vertically. UM. All fault
lines are basically where plates are still pressing together very tightly, right,

(12:03):
and when when they pressed together, they're eventually going to
get locked because of friction, right, But the pressure is
still going. They still want to move. So all this
potential energy is being built up, and as it builds
and builds and builds, the pressure eventually overcomes the resistance
and all of a sudden you have a slip. It breaks,
it does, and that's that's actually the epicenter of the

(12:25):
focus of the earthquake where that happens right there. That
is the key, that is what an earthquake is, Yes,
is when the initial fault break or more that happened
later on occur. We really paid that out in a
dramatic fashion, didn't we. Yeah, it didn't feel that dramatic
to me. It will when we listen to that, maybe
because I know the ending, so chuck right, they can't

(12:48):
believe you gave it away. So fault zones, that's that's
where there's lots of faults together connected, right. Yeah, So
one of those one of those faults slipping one of
that UM a place where the potential energy you turns
kinectic all of a sudden can actually trigger um faults,
or it can actually trigger movement along other faults that
are connected those fault zones you mentioned, right, That's why

(13:11):
earthquakes often happen in a series. It's more than more
than one, right, and they almost always happened along the faults.
But I know that very uh one, very famous earthquake
in eighteen eleven and eighteen twelve, which I didn't Did
that happen in like December thirty one, in January one
or what? I don't know. That's a good point twelve

(13:32):
one long earthquake. Yeah, it would be. We'll find out
about that. But that occurred in the middle of a plate,
in the middle of the North American continental Plate, which
is odd at the time, but it was They found
out later that deep beneath the earth that was in
fact a six hundred million year old fault zone. So yeah,
there you have it. Yeah, so it's it's some way
or another there's a fault zone involved. Indeed, so chuck um,

(13:55):
we actually have a way to measure earthquakes. We measure
them through their seismic waves, right, make waves, which seismic
waves are the energy that radiates from their focus and
it it acts as a wave much like a wave
in water, right, like if you were to throw sound
waves rock and a pond, that kind of thing. There's
there's two different types of waves, two major types of waves.

(14:18):
You have body waves and you have surface waves. So
let's talk about body waves first. Yes, they move through
the inside of the earth, the inner part of the earth. Right.
And well there's two different kinds of it's primary and
secondary body waves waves, pea waves or s waves. It's
easy to remember mnemonic induction and lucid dreaming, etcetera. Right.
They travel about one to five miles per second. The

(14:42):
pea waves too. Yeah, and they're actually they can move
through solid liquid or gas. Yes, they cannot be stopped. No,
so they can actually go from one end of the
Earth to the other. Well, they do too every time.
Isn't that correct? I don't know. I think that's what
it says. We'll find out. Uh. And these these the
pea waves, actually they affect the stuff that they're moving,

(15:03):
like say, rock horizontally, so it shakes back and forth
on a horizontal plane. Okay, And like you said, they're
the fastest, so they get there first. But I got
the impression that they caused the least amount of damage.
Then you have secondary waves, right, secondary body waves. Yeah,
that's the problem. Well, they're the first problem because they
displaced rock perpendicularly to the direction of the wave. Right.

(15:28):
So you remember the movie Tremors, So you remember the
worms going underground and it was displacing dirt up on
the Earth's surface. Same thing. That's like, that's like a
secondary wave and s wave. I love that you're quoting
tremors are scientific? Backup. I love that one. You It's

(15:48):
great spread ward classic. So so actually that was Kevin Bay. Yeah,
that was such a good one. It's probably one of
my top five. Yeah. Um, so let's let's talk about
surface waves you want, Well you should actually just say
real quick though, that they don't travel through solid material,
the secondary so they stopped liquid the liquid Earth's core,

(16:12):
or if you believe in hollow war theory, they would
stop when it became hollow because it doesn't travel through
gas apparently either, right, Yeah, they would stop at the
temple of Doom. Yeah, according to dollarwar theory. Can we
talk about surface waves yet? Yes, we're there. Let's see it.
They're like more like the waves in a body of water, right,
they move the earth up and down. Did you see

(16:33):
some of the pictures in this article. This is a
really cool article for pictures. There's actually a page, picture
page of nothing but earthquake aftermath pictures and they're cool
interactive things too. When you talk about the plate shifting,
some animations you can click on. Did you see the
one with the railroad tracks? What was that, Peru? I

(16:54):
don't remember. There's a picture in this article of railroad
tracks that um basically just make a perfect s because
of the surface waves that hit it during an earthquake. Well,
and the crops that shifted to that being in a
straight line, they had the wave in them. Yeah, so
that's all due to surface waves. Surface waves are the
ones that caused the most damage as far as we're concerned.

(17:15):
If you're like, you know, a mole man or something,
you're probably going to be more afraid of secondary body
waves up top side. We're afraid of, you know, the
surface waves. The l waves are long waves is what
they're called as well, top top dwellers that we are, right,
so they caused the worst damage, and because they move
the earth up and down, like you said, a wave,
a water wave in the ocean, Yeah, exactly, which we don't.

(17:37):
We don't build our buildings generally to withstand wave like motion. No. Well,
they've done a lot of work though, to build buildings
that can rock back and forth and move a little
bit and have the foundation shift. It's called earthquake. What
we were talking about reinforcement. Sure, some of my apartments
in l A actually had were reinforced. You could tell,

(17:58):
like in the walls they would have these bars running
up in stuff. But yeah, as far as in the
Japan's on like the cutting edge of of earthquake proofing
of everything. Yeah, yeah, a lot of earthquakes in Japan.
Huh Yeah, and robots and volcanoes. Where are we now, Josh?
You want to talk about Richter scale yet or I

(18:18):
think that's the inevitable conclusion. So, Josh, the Richter scale
is uh, as most people know, records a magnitude of
the earthquake. Um. It's logarithmic, so that means that the
whole number jump means it increases tenfold. So a six
on the Richer scale is actually ten times as powerful
as the five, and the nine times as powerful as
the seven. How about that. Yeah, that's serious business. And

(18:41):
what the Richer scale does is it measures that that
wave amplitude of the seismic energy of a quake. And um,
so that's the one you always hear about, Like I
talked about that one in Pepua, New Guinea was a
six point seven, right, which is large. Anything below a
three generally doesn't get much attention. This is just a
little tremor my micro quake. It's kind of hard to say.

(19:02):
And that's the that's the vast majority of earthquakes or
three year less. Right. Yeah, you won't see anything below four.
You won't see a lot of damage going on. But
anything seven and above is a pretty serious business. And
then the record is a nine point five. I looked
this up nineteen sixty Chile. Right, you're ready for some
stats of my own? Look at you. I mean, imagine

(19:24):
at nine point five on the Richter's kill it's immense. Um,
there were sixteen hundred and sixty five people killed, three
thousand injured, in two hundred thousand homeless in Chile alone, um,
along with five hundred and fifty million dollars in damage
property damage nine sixty. So that's ninety that's the impression

(19:49):
I have you. Um, it created a tsunami that killed
sixty one people and caused seventy five million dollars with
the damage all the way in Hawaii, you're kidding, And
in Japan and there were a hundred and thirty eight
deaths and fifty million dollars worth of damage. Yeah, and
it just kind of goes on from there. You know,
what they said about that eighteen ten slash eleven earthquake

(20:10):
in Missouri was that they could the church bells in
Boston rang from the from the reverberation. I know that's nuts. Yeah,
I want to verify that. But big old earthquake right there.
So what you're talking about though, with the assessing the
damage that is actually the Mercali scale, the damage done
by the earthquake, which has figured out many days or

(20:31):
weeks later, not like the Richter scale. I call that
the y us God scale, right. Yeah, it's it's described
in Roman numerals up to twelve, which you can also
say is x I I and x i I is
where there um is evident structural damage. The ground is

(20:51):
opened up, sure like in the movies. Yeah. Um, and
there's been at least the tsunami or mudslide or some
other disaster. Yeah, my brother felt the earthquake when he
was in l A. Did he look handsome and much
more exciting things happen to him out there? His He
he said it felt like a buzzing, like a real
loud buzzing, and then he looked at his closet and

(21:12):
the clothes were shaking, and you know it's over then,
you know, as soon as you realize what's going on,
it's over. Yeah. I read about the nineteen o six
San Francisco earthquake. They said that the sensible duration of
the earthquake it was a minute really, which I imagine
probably felt like an hour, killed three thousand people. Well,
that's that just goes to show you the kind of
devastation if it only takes sixty seconds to wreak, that

(21:34):
kind of havoc what's going on and fires that broke
out after buildings collapsing, very scary stuff. So, Chuck, Well,
we can't predict earthquakes. We do need to close with that.
I think. Okay, they've come a long way and determining
the the epicenter, and they can predict after shocks pretty

(21:55):
well now, and they can say, hey, do you to history,
you you're likely to have an earthquake because we think
things are moving in your area. The plates may be moving,
but they can't accurately say when it's gonna happen. Yeah.
I remember being a little kid, and I think some
scientists came out and said, there's going to be a
massive earthquake and you know San Francisco or California that's

(22:20):
going to basically cause the state to break off. That's
a pretty fun thing. But they couldn't They couldn't say
when it was gonna happen. They said within the next
X number of decades. Scare a student day at your school. Yeah,
so if you have any relatives in California, they will
likely die. And I do have relatives in California too,
you did at the time. I still do. Hey, Aunt Barbe, Okay, yeah,
Aunt Barbe, Aunt Barbe, cousin just me and cousin Wolf

(22:43):
along with cousin Peter, cousin John, and I think that's
it out there. Oh and uh aunt Donna. Wow, yeah,
well they live in California. Wolf he actually you want
to know a wolf he story. This may or may
not make it in the final version. But I'll tell you, Chuck,
um cousin. Wolfe was born Eric Wolf right his first

(23:05):
middle name. When he was like eleven or twelve, he
decided he preferred the name wolf more. So he got
his parents permission and went down to the Clerk of
Courts and changed his name to Wolf Eric and he's
been Wolfie ever since. That's pretty funny. What a guy. Uh.
And then, um, I guess we already kind of talked
about building construction. Is when the uniform building putt came about,

(23:28):
and it's it's a set of standards basically two people
have to follow now, right, whether you're in fulsome prison
San Quentin, Japan, you gotta follow certain standards. Sure, oh yeah,
especially Chile. So that's earthquakes in a nutshell. And we're
not doing this one again unless they figure out that
the continental drift theory was complete rubbish, right yeah. Oh,

(23:52):
and also we should probably tell people, Chuck, there's an
article on how to survive an earthquake at how stuff
works dot com. You can type of five earthquake in
the handy search parts, save yourself a few keystrokes and
that will bring that right up. Good idea. And also
you can just type in earthquakes and I will also
bring up the how earthquakes work article with all those
super cool pictures. Right, yeah too, listener mail buddy, Okay, Josh,

(24:19):
I'm just gonna call this sleep paralysis deluge. It was
a deluge, wasn't it. Yeah, last well, it will be
last week now, a couple of weeks ago, probably when
this is released. We had a listener bail from drowsy
Dug in Oregon who had the pick suit man. He
was awake but couldn't move and very frightened and apparently

(24:40):
everyone on the face of the earth, and this is
sleep paralysis. But us and I had heard of sleep paralysis, uh,
never done a whole lot of research on it, but
rest assured we will do an episode on this now.
So here's the delusion of paper cup chuck. Yeah. Well,
I also want to say I did not respond to
any of those emails, and I am very sorry, but

(25:00):
we got literally over a hundred of them and I
just didn't have time. But it did read them, so
no offense people. And out of all the emails we
got about that one from medical and psychological professionals, I
went with Madeleine, our new thirteen year old fan because
hers was so good. Hey, guys that just listen to
your podcast with Drowsy Doug. It sounds like what happens

(25:21):
to me. I would be laying in bed and wake up.
Unfortunately I'm too lazy and tired to get up. But
then I would see things out of this world. Like
one time I woke up and I was too tired
to get up, and I saw it seems to be
a common thing, And I saw in my huge half
a sofa sized mirror my sister. Half her body was

(25:42):
in the mirror, frozen while the rest of her was
bending and moving around on my dresser. Awesome. Another time
I saw army guys getting pulled onto my roof. Please
don't give me any cures for this, because I like
seeing Navy seal guys climbing to my roof. So that's
from Madeleine, and Madeleine sounds like you my have a
little case of sleep paralysis. But as long as there's

(26:03):
no pig suited people or don't worry faces, we'll follow
up with the podcast on this and condition. And a
lot of people sounds like they have it. Actually a
lot of people that run in Yeah, they're right there
with Doug. Keep making these promises, don't you. Yeah, we'll
do it all right. Well, if you want to basically
boss chucking me around and get us to do a podcast,
send us your ideas to stuff podcast at how stuff

(26:27):
works dot com. For more on this and thousands of
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