Earthquakes don’t just slam into existence—they whisper first. Scientists recently uncovered a creepy hidden stage before the ground shakes: a “silent creep.” During this phase, tectonic plates grind so slowly and quietly that no one feels it—but stress is secretly piling up. In lab experiments with plexiglass, researchers recreated how Earth’s plates behave. They saw tiny cracks, called “nucleation fronts,” crawling forward under pressure. At first, they move like lazy shadows. But once they grow big enough, they suddenly speed up, unleashing the explosive force we know as an earthquake. This discovery might be our best shot yet at reading Earth’s hidden messages before disaster strikes. Credit: TheEventRecorder / YouTube 2025 Sagaing Earthquake Archive / YouTube San Andreas / New Line Cinema 2012 / Columbia Pictures CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0/: Fault3: By Anynobody, https://commons.wikimedia.org/w/index.php?curid=4084355 Fault2: By Anynobody, https://commons.wikimedia.org/w/index.php?curid=4084280 CC BY 4.0 https://creativecommons.org/licenses/by/4.0: Animated Tectonic Plates Collide Loop: By LasquetiSpice/sketchfab, https://skfb.ly/o9FWz Animation is created by Bright Side.
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00:00Before an earthquake shakes the ground, something sneaky might happen first.
00:05A slow, quiet movement with no shaking at all.
00:08No one is aware that right under their feet, the land is preparing to tremble violently,
00:14wreaking havoc, bringing destruction and devastation.
00:17A new study shows that such a slow creep might be how earthquakes begin.
00:23To figure this out, scientists didn't start with giant pieces of the Earth.
00:26Instead, they went into a lab and used clear plastic sheets called plexiglass.
00:32They pushed two sheets of plexiglass sideways against each other,
00:36just like how tectonic plates, huge chunks of Earth's crust, push against each other underground.
00:42As they pushed, the plastic cracked, kind of like what the Earth does during an earthquake.
00:48And even though it was plastic and not rock, the physics, the way things break and move, was the same.
00:55Earthquakes happen when two tectonic plates try to slide past each other, but they get stuck.
01:02The edges between them don't move easily because of something called friction.
01:06It's kind of like when your shoes grip the ground.
01:08Over time, the plates keep trying to move, and stress builds up.
01:13Think of it like bending a stick.
01:15At first, it doesn't break.
01:16But if you keep pushing, it will eventually snap.
01:19The spot where the plates are stuck is called a fault.
01:23And there's a thin, brittle part in that fault.
01:26By brittle, I mean that it doesn't bend.
01:29It just breaks.
01:31Here's how it happens.
01:33First, a tiny crack forms.
01:35It's small and moves slowly.
01:36There's no shaking yet.
01:38But something is already happening under the surface.
01:41The crack spreads, building up more energy.
01:44When it finally reaches the edge of the brittle zone, boom, it speeds up, suddenly racing forward really fast, almost as fast as sound.
01:53And that's when the Earth starts to shake.
01:56So scientists decided to find out how that very first crack starts.
02:01They conducted their experiment, whose setup was similar to a type of fault in the real world called a strike-slip fault, like the San Andreas fault in California.
02:10Even though the materials, plastic versus rock, are different, the way cracks form and move is exactly the same.
02:19The experiment has helped scientists understand that earthquakes don't always start suddenly.
02:24Sometimes there's a slow, quiet start, like a warning sign before the big quake.
02:30This early stage of an earthquake is called a nucleation front.
02:34It's like a seed of a crack, gently creeping through the material long before any actual rupture happens.
02:41This quiet and slow movement doesn't release energy into the surroundings.
02:46At first, scientists thought of cracks as simple one-dimensional lines, like a straight tear in paper.
02:52But something didn't add up.
02:53The slow-moving nucleation front wasn't behaving like a normal, fast-moving crack.
02:59And it wasn't clear why or how it suddenly sped up and became an earthquake.
03:04The answer came when scientists realized they had to think in two dimensions instead of one.
03:10Instead of imagining the crack as just a fine line, they began to think of it as a patch, like a growing circle,
03:17that starts at the surface where two materials touch.
03:20As this patch spreads out, more material along its edge has to break.
03:25The important thing here is that the energy needed to break the material is related to how long the patch's edge, or perimeter, becomes.
03:34The bigger the perimeter, the more energy it takes to keep breaking.
03:37That's why this patch moves slowly at first.
03:40It doesn't yet cause the violent shaking we associate with an earthquake.
03:44Because it moves without sending shaking waves, this stage is called aseismic.
03:50Eventually, the growing crack patch spreads beyond the special brittle zone, where the materials are stuck.
03:57Outside this zone, the energy needed to keep breaking the material doesn't increase anymore.
04:03Instead, there's now extra energy building up, more than what's needed to keep the crack growing slowly.
04:09This extra energy doesn't stay quiet.
04:12It suddenly powers the crack to move much faster, turning it into a full-speed rupture.
04:17That's the moment when the earthquake begins, and the ground starts to shake.
04:22These findings help explain how earthquakes might start off slow and silent before quickly turning dangerous.
04:28They show that small, slow cracks can suddenly transform into powerful, fast-moving ruptures if the conditions are right.
04:37Scientists believe that they can learn to detect the aseismic stage before a crack speeds up.
04:42It might one day be possible to predict earthquakes, or at least understand the warning signs better.
04:48Now, even though earthquakes are only the third most common type of natural disaster, they cause the highest number of fatalities.
04:56NASA plays an important role in studying earthquakes by using satellites that orbit the Earth.
05:01These satellites collect data and images that show how the ground changes after an earthquake.
05:07For example, they can detect when the land shifts, rises, sinks, or cracks.
05:13These surface changes help scientists learn more about the strength and impact of earthquakes.
05:18NASA's satellites can also track changes in nighttime lights.
05:22If a city goes dark after a quake, that's a clear sign that the area may have lost power and could need help.
05:28Now, how about we talk about the most common earthquake myths, like the one about mega-quakes?
05:34Some people really worry about super-huge earthquakes, but there's a limit to how big they can get.
05:41The size of an earthquake depends on the size of the fault where it happens.
05:45A longer and deeper fault can cause a bigger earthquake.
05:49For example, the San Andreas Fault in California is long, about 800 miles, but not very deep, around 10 to 12 miles.
05:57This makes earthquakes bigger than magnitude 8.3 on that fault very unlikely.
06:03The biggest earthquake ever recorded happened in Chile in 1960.
06:08It had a magnitude of 9.5 and occurred on a huge fault that was almost 1,000 miles long and 150 miles wide.
06:17Technically, there's no set limit on the magnitude scale.
06:20But an earthquake bigger than magnitude 12 would need a fault larger than Earth, which just isn't possible.
06:27Now, earthquakes can happen near the surface or deep underground.
06:31Most occur in Earth's crust or upper mantle, down to about 500 miles deep.
06:36But the deepest ones happen only at subduction zones, places where one part of Earth's crust slides under another.
06:43In California, almost all earthquakes happen in the top 15 miles of the crust.
06:49One exception is the Cascadia subduction zone in Northern California, which continues up through Oregon, Washington, and Canada.
06:57Another misconception is that the ground can open during an earthquake.
07:01But usually, that only happens in movies.
07:04A giant crack opening and swallowing things up during an earthquake is just fiction.
07:09In real life, the ground on either side of a fault slides past each other.
07:14It doesn't pull apart or open wide.
07:16Small cracks or holes can happen during landslides or ground failures, but not along the actual fault line itself.
07:24Faults don't open up, because if they did, there'd be no friction.
07:27And without friction, there wouldn't be an earthquake at all.
07:31Now, some people think California could break off and sink into the ocean during an earthquake.
07:36But that's not how it happens.
07:38The ocean floor is just lower land with water above it.
07:41California can't fall in.
07:44What's really happening is that southwestern California is slowly sliding north toward Alaska along the San Andreas Fault.
07:51The Pacific Plate, which California sits on, is moving about 2 inches per year, about as fast as your fingernails grow.
07:58So, in about 15 million years, Los Angeles and San Francisco could be neighbors.
08:05And in 70 million years, Los Angeles might be sitting near Alaska.
08:09I can't wait.
08:11People often wonder whether an aftershock can be bigger than the earthquake itself.
08:16Aftershocks are smaller earthquakes that happen in the same area after a larger one.
08:21They're like our planet's way of settling down after the main shock.
08:25But if an aftershock turns out to be bigger than the first earthquake, then we call the bigger one the main shock, and the earlier one becomes a foreshock.
08:34About 5 to 10% of earthquakes in California are followed by a stronger one within a week.
08:40It's also possible for two quakes in the same area to be about the same size.
08:45However, very large earthquakes are rare.
08:48So, it's even rarer to see two huge ones happen close together.
08:53That's it for today.
08:54So, hey, if you pacified your curiosity, then give the video a like and share it with your friends.
08:59Or, if you want more, just click on these videos and stay on the bright side!
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