In the past decades, numerous magnitude seven or stronger tremors have been reported. Researchers have learned that an underwater volcano sitting on a sinking tectonic plate off the coast of Japan could be the root of the Earthquakes in the past 40 years.
Underwater Volcano May Be The Root Of Magnitude 7 Earthquakes
A new study discovers that an ancient underwater volcano off the coast of Japan that is riding a sinking tectonic plate may have caused many mysterious large earthquakes by grinding against another tectonic plate above it.
Approximately 25 miles (40 kilometers) off the east coast of Japan is the Pacific tectonic plate, home to the dormant underwater volcano known as Daiichi-Kashima seamount. Three tectonic plates meet there: the Okhotsk plate to the north is slipped beneath by the Pacific plate to the east and the Philippine plate to the south.
According to research co-author Euneseo Choi, an associate professor at the University of Memphis' Center for Earthquake Research and Information, the seamount is situated on a portion of the plate that started to descend into Earth's mantle between 150,000 and 250,000 years ago.
Lead author Sungho Lee, a postdoctoral researcher at the University of Memphis, noted that although the seamount is now less than 31 miles (50 km) deep, it is still close enough to the surface to cause earthquakes. While most of the seismic activity on the seamount is represented by tiny tremors, Lee told Live Science that there have been a few earthquakes between magnitudes seven and 7.8-in 1982 (7), 2008 (7), and 2011 (7.8)-that have not been adequately explained by prior study.
The seamounts scattered across the surface of a tectonic plate scrape against the overriding plate's bottom as it subducts beneath another plate. According to 2008 research, this friction was only strong enough to cause extremely minor tremors rather than earthquakes.
However, more recent data show the reverse, per Lee. Based on seismic data collected at the ocean floor in Japan, seamounts occasionally become trapped as they travel along a subducting plate and face intense resistance. "The seamount itself is almost stationary because it has very strong friction," Lee stated.
Stress builds up on the leading edge of the seamount as it penetrates the overriding plate. The rest of the subducting plate continues its slow slide into Earth's mantle, but the area surrounding the seamount locks up and stops in what the authors called a "hang up" event.
Massive Seamount Twice As Tall As Burj Khalifa Discovered
Meanwhile, researchers recently discovered a huge underwater volcano in the Pacific Ocean. It was so massive that it was twice as tall as Dubai's Burj Khalifa, the highest structure in the world.
The seamount was discovered by a Schmidt Ocean Institute (SOI) mission in international waters, approximately 84 miles outside of Guatemala's exclusive economic zone. The seamount is about 13,100 feet below sea level and peaks at about 7,900 feet. It rises 5,249 feet above the ocean floor.
It was the third seamount that had been found since the launch of the research vessel Falkor in March.
RELATED ARTICLE: How Do Volcanoes Erupt, and How Scientists Study and Predict These Eruptions
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