00:00There's a powerful force hiding underground, where tectonic plates meet, and one forces
00:08another under it.
00:09This happens in the Pacific and Indian Oceans.
00:12Strain builds over centuries.
00:14The tension is unbearable until the megathrust awakens.
00:19The Earth shakes with a magnitude that can exceed 9 points, more powerful than any other
00:24earthquake.
00:26When the seafloor suddenly gets pushed up fast, it sends a huge ripple across the water,
00:31and a tsunami of huge force is out.
00:34These waves are called tele-tsunamis, and they cross entire ocean basins, ready to take
00:39over coastlines thousands of miles away.
00:43The thrust fall stretches over 600 miles.
00:46The Earth is not just shaking, it feels like it's tearing apart.
00:50This is the power of a megathrust earthquake.
00:53Those caught in its path will have to fight for their lives.
00:58Japanese authorities recently had to issue their first-ever megaquake advisory.
01:03It happened because of a strong tremor on the edge of the Nankai Trough ocean floor
01:08zone.
01:09In the end, most of the warnings were lifted, and there wasn't much damage from the 7.1
01:14magnitude earthquake.
01:16Parts of southwestern Japan started to shake, and the super-fast trains in Japan slowed
01:21down to stay safe, which made travel slower for everyone.
01:25But everyone is staying alert, as they know about the risk of a megathrust earthquake
01:29that could happen within the next few decades in the Nankai Trough.
01:34The tectonic plate under the Philippine Sea is slowly sliding underneath the land where
01:39Japan is, moving just a few inches every year.
01:43The last big earthquakes from this area happened in 1944 and 1946, both with a magnitude of
01:498.1.
01:51These quakes have caused a lot of destruction in the country.
01:54The next megathrust earthquake in the region, if it does happen, could be between a magnitude
02:008 and 9.
02:02Scientists still can't agree on how likely this mega-earthquake is to happen, but it
02:06could be up to 80% certainty.
02:11On the other side of the Pacific, scientists from the U.S. Geological Survey have studied
02:16a dangerous area along the U.S. West Coast.
02:19It's called the Cascadia Subduction Zone, and it stretches from Northern California
02:25to Northern Vancouver Island in Canada.
02:28Over the past 14,200 years, there have likely been at least 30 big earthquakes in this region,
02:34when major quake happens every 500 years on average.
02:38But for a long time now, Cascadia has been quiet, and it worries scientists.
02:43They think this might be because the area is locked, meaning the tectonic plates are
02:48stuck together and building up a lot of pressure.
02:51Eventually, a part of the seafloor could suddenly break and move by several feet.
02:57The shaking would be just 5 minutes, but it would create a powerful tsunami as the seafloor
03:02shifts that would last for 10 hours.
03:05If it happens, it's going to be the worst natural disaster in the country's history,
03:09according to experts.
03:11The ground on some inland hills could turn into something like quicksand.
03:15This would cause the hillsides to slide and crumble, taking down roads and bridges.
03:21Around 620,000 buildings could be badly damaged or even collapse, including about 100 hospitals
03:28and 2,000 schools.
03:30People in Washington state might have to take care of themselves without help for two weeks,
03:35finding food, water, and shelter on their own.
03:41Scientists are studying slow-slip events, where the tectonic plates move very slowly
03:45over weeks or months, releasing some energy but not enough to stop a big one.
03:51Every time the magnitude of an earthquake goes up by just one number, the energy it
03:56releases is 40 times bigger.
03:59So we'd need about a million small earthquakes every day for 500 years straight to release
04:04the same energy as one huge magnitude 9 earthquake.
04:08But these small earthquakes might be clues that a bigger earthquake is coming.
04:13To better monitor the Cascadia Fault, experts are mapping the fault more accurately and
04:18adding better monitoring tools offshore.
04:22Scientists receive over $10 million to install seismic sensors and seafloor pressure gauges
04:27on a fiber-optic cable off the coast of Oregon.
04:31The goal is to be ready to warn people and potentially save lives when a big earthquake
04:36strikes.
04:40A sharp megathrust earthquake happened in this part of the world in 1964.
04:45It went down in history as the Great Alaska Earthquake and had a magnitude of 9.2.
04:52It lasted for more than 4 minutes, making it the most powerful earthquake in the history
04:56of the U.S. and North America.
04:59The ground shook so hard that it caused huge cracks and landslides.
05:04In Anchorage, many houses, buildings, and roads were destroyed because they weren't
05:08built to handle such a big earthquake.
05:11In some places, the land was permanently changed.
05:14For example, the coastline near Kodiak and Hinchinbrook Island was lifted by 30 feet.
05:20In other areas, like Gerwood and Portage, the ground sank by 8 feet.
05:25They had to rebuild roads higher so they wouldn't be flooded by the time.
05:30A huge 27-foot tsunami wiped out the entire village of Chenega.
05:35Many coastal towns were heavily damaged, not just by the earthquake, but also by tsunamis
05:40in the fires that followed.
05:42After the main earthquake, there were thousands of smaller aftershocks for months.
05:49A moderate earthquake of magnitude 4.4 shook Los Angeles in August 2024.
05:56Once it was over, the LA Fire Department checked around the city and didn't find any major
06:00damage or anyone hurt.
06:02In the nearby city of Pasadena, which is close to the earthquake's epicenter, a water pipe
06:07burst inside City Hall, and everyone had to leave the building.
06:11Thankfully, there was no danger of a tsunami.
06:14The best we can do to avoid panic in such situations is to be prepared.
06:21Japan is one of the places on Earth where earthquakes happen the most because it sits
06:25on the edges of four tectonic plates.
06:28Around 1,500 of these earthquakes each year are noticeable.
06:33Because of this, the people in Japan have learned to live with earthquakes.
06:37The 1950 law set a rule that buildings should be able to handle earthquakes up to a magnitude
06:437 without falling apart.
06:46An update 30 years later said that buildings should only have minor damage in such earthquakes
06:51and still work as usual.
06:53But if an earthquake is even stronger, the law says the building's main job is to not
06:58collapse and save people's lives.
07:01At the most basic level, buildings are made stronger with thicker beams, pillars, and
07:05walls so they can handle shaking better.
07:08Another technique is placing special pads made from materials like rubber at the base
07:13of a building.
07:14Some buildings are even built on thick layers of padding that separate them from the ground
07:19completely, which helps protect them during an earthquake.
07:22A skyscraper might sway back and forth a lot, moving up to 5 feet.
07:27To stop it from getting damaged, engineers can add something called dampers every second
07:32floor all the way to the top.
07:35These dampers are like giant bicycle pumps, but instead of air, they're filled with liquid.
07:40When the building shakes, the dampers push against the liquid inside them.
07:45Even though the liquid doesn't squish very much, it can still absorb some of the shaking.
07:52When they're building tall skyscrapers, engineers try to make the structure as simple and balanced
07:57as possible.
07:58This means having each floor the same height and placing the support columns evenly.
08:04But sometimes, architects who design skyscrapers don't want to make these compromises because
08:09they have creative ideas for how the building should look.
08:13Then they have to find compromise solutions.
08:16For example, Tokyo's Skytree Tower, one of the tallest buildings in the world, is designed
08:21in a futuristic style but also includes special features to protect it from earthquakes.
08:27It has a central pillar, like in traditional Japanese pagodas, and seismic dampers that
08:32help absorb the energy from an earthquake, keeping the building safe.
08:39That's it for today!
08:40So, hey, if you pacified your curiosity, then give the video a like and share it with your
08:44friends!
08:45Or if you want more, just click on these videos and stay on the Bright Side!
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