September 20, 2017

JAPAN: A Magnitude 6.1 Earthquake Struck Off Japan's Coast Along Pacific Ring of Fire Today, Like Recent Mexico Earthquakes. :o The Science Behind Why There Are So Many Earthquakes In Mexico?

written by CNN newswire
Wednesday September 20, 2017

A day after a powerful earthquake along the Pacific Ring of Fire hit Mexico, another large quake hit the same area of seismic activity on its opposite side, across the Pacific Ocean, on Wednesday: a magnitude 6.1 off the coast of Japan.

Wednesday’s quake hit at 4:37 p.m. local time, or 8:37 a.m. PT, according to the U.S. Geological Survey. Its epicenter was about 200 miles off the coast of Japan, and about 315 miles northeast of Tokyo.

The quake hit about 228 miles from Fukushima, the site of the nuclear power plant that was inundated following a tsunami triggered by a magnitude 9.1 earthquake on March 11, 2011. That much more powerful quake 6 1/2 years ago was much closer to shore.

The 40,000-kilometer (25,000-mile) Pacific Ring of Fire stretches from the boundary of the Pacific Plate and the smaller plates such as the Philippine Sea plate to the Cocos and Nazca Plates that line the edge of the Pacific Ocean.

About 80% of all earthquakes strike in the Ring of Fire, according to Hongfeng Yang, a seismologist at the Chinese University of Hong Kong.

People are most at risk in Chile, Japan, the US west coast, and other island nations including the Solomon Islands to the western seaboard of North and South Americas.

They are at risk because they lie on subduction zones that are locked so tectonic energy must be released by large earthquakes.

How did the Ring of Fire form?

Tectonic plates are massive slabs of the Earth’s crust. These move constantly above the mantle — a layer of solid and molten rock below the Earth’s crust.

The Ring of Fire was formed as oceanic plates slid under continental plates.

Volcanoes along the Ring of Fire are formed when one plate is shoved under another into the mantle — a solid body of rock between the Earth’s crust and the molten iron core — through a process called subduction.

Large earthquakes — which risk triggering tsunamis — also occur in subduction zones.

How are earthquakes triggered?

Earthquakes represent the energy release from the interior of the Earth, where huge amount of heat is stored.

The heat drives the plates to move. When two plates move against one another and produce friction, it causes energy to build up. When the energy is released it triggers an earthquake.

“It takes tens of thousands of years for the energy to build up, but only a matter of seconds for it to be released,” said Hongfeng Yang, a seismologists at the Chinese University of Hong Kong.

Tectonic plates usually move an average of a few centimeters each year, but when an earthquake strikes, they can move several meters per second.

Can earthquakes be predicted along the Ring of Fire?

As with the Sept. 7 earthquake off the west coast of Mexico, seismologists can’t yet predict when or where earthquakes will strike, or how large they will be.

Some researchers argue that there are certain conditions — such as hydraulic fracturing when we drill deep into the sea to extract energy resources — induce earthquakes. But there’s no hard scientific evidence to back this up.
Sky News
written by Aubrey Allegretti, News Reporter
Wednesday September 20, 2017

Mexico has a deadly and unlucky history with earthquakes.

It is frequently hit, the latest quake coming on the 32nd anniversary of the 1985 disaster that killed more than 5,000 people, and less than two weeks after an 8.1 magnitude hit the southern coast.

The Central American country suffers so much because of its position on a large grid of tectonic plates, on which all the Earth's countries and seas sit.

Mexico is on the edge of two the world's largest - the North American and Pacific plates - as well as the smaller Cocos plate.

It also falls on the 'Ring of Fire', a horseshoe shaped area around the edges of the Pacific Ocean, from Australia to the Andes, along which 90% of all earthquakes occur.

Mexico's location makes it particularly vulnerable to earth tremors.

The Earth's plates grind against each other all the time. Sometimes they get stuck and pressure builds-an earthquake is the sudden and violent release of this pressure.

On top of this, the Cocos plate is denser than the landmass of Mexico itself, meaning the country's soft earth crumbles more easily.

This combination makes it one of the most seismically active countries on the planet.
Mexico City, where more than 200 people have been killed in the latest tremor, was also mostly built on a former lakebed, making it even more susceptible.

Japan, Turkey, Indonesia, Pakistan, Nepal, the Philippines, India and El Salvador are also among the countries most vulnerable to earthquakes.

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