why does japan experience earthquakes and tsunamis

A magnitude-7. 0 earthquake struck southern Japan today, less than two days after a 6. 2-magnitude temblor rocked the same region, triggering tsunami advisories in the area. The most recent earthquake struck the Kumamoto region on Japan s Kyushu Island early Saturday (April 16) at 1:25 a. m. local time (12:25 p. m. ET on April 15),
(USGS). The smaller 6. 2-magnitude quake on Thursday (April 14) killed nine people and injured hundreds more,. With residents of the Kumamoto region reeling from two sizable earthquakes in as many days, and with memories of the that devastated Tohoku, Japan, in 2011 not far from people s minds, what is it about this part of the world that makes it so seismically active? [ For starters, Japan is located along the so-called, which is the most active earthquake belt in the world. This ring is actually an imaginary horseshoe-shaped zone that follows the rim of the Pacific Ocean, where many of the world s earthquakes and volcanic eruptions occur. Within the Ring of Fire, several tectonic plates including the Pacific Plate beneath the Pacific Ocean and the Philippine Sea Plate mash and collide. The Earth s surface is broken up into about a dozen or so major chunks that are all moving around. Where they all interact at their edges, interesting things happen, said Douglas Given, a geophysicist with the USGS in Pasadena, California. Today s earthquake seems to have been caused by the Philippines Sea Plate diving underneath the Eurasia Plate, according to Paul Caruso, a geophysicist with the USGS. While Japan is no stranger to earthquakes, the 7. 0-magnitude temblor is one of the largest ever recorded in this part of southern Japan, Caruso told Live Science.

The second-largest was probably on March 20, 1939 there was a magnitude-6. 7 in this area. And we ve had magnitude-6. 5 and magnitude-6. 3 earthquakes, but this is the largest quake that has been measured in that vicinity, he said. A tsunami advisory was issued after today s earthquake, but it was subsequently lifted by the Japan Meteorological Agency, and there are currently no major in effect. Not all earthquakes trigger tsunamis, Caruso said. In general, there are three key ingredients that can produce a dangerous earthquake-tsunami combination, he added. First, the earthquake must be at least a magnitude-7 temblor. Second, the quake s epicenter has to be underneath the ocean, Caruso said. And finally, the earthquake has to be shallow. We have quakes around Fiji all the time, but those are sometimes 400 miles [640 kilometers] underground, so they, he said. Today s earthquake was shallow about 6 miles (10 km) underground but the epicenter was on land, meaning there aren t likely to be any dangerous tsunamis as a result, Caruso said. Given said he hasn t seen many damage reports yet, but Japanese authorities and scientists at the USGS will be monitoring the area for potentially dangerous aftershocks, which are smaller quakes that follow the largest event in a series and that generally decrease in strength.

This seems to be a pretty energetic sequence, and there are lots of large aftershocks, Given told Live Science. And of course, after a large earthquake, structures are often weakened as a result. Additional damage can be expected. Residents of the area should expect more shaking in the coming days, according to Caruso. We can say for certain that there are going to be more aftershocks in this area, he said. Exactly when and how big they re going to be is difficult to say, though. No one can predict that. Follow Denise Chow on Twitter @denisechow. Follow Live Science @livescience, Facebook Google+. Original article on. What caused the tsunami? The most powerful earthquake recorded in Japanese history, magnitude 8. 9. The tremors were the result of a violent uplift of the sea floor 80 miles off the coast of Sendai, where the Pacific tectonic plate slides beneath the plate sits on. Tens of miles of crust ruptured along the trench where the tectonic plates meet. The earthquake occurred at the relatively shallow depth of 15 miles, meaning much of its energy was released at the seafloor. How does the earthquake compare with others? This was the sixth largest earthquake in the world since 1900, when seismological records began. The most devastating earthquake to strike Japan was in 1923, when a magnitude 7. 9 tremor devastated Tokyo and Yokohama and killed an estimated 142,800 people.

The Kobe earthquake in 1995 was a magnitude 6. 9 and caused more than 5,000 deaths and injured 36,000 others. The earthquake that wrecked Christchurch in New Zealand last month was a magnitude 6. 3 event. Around 30 times more energy is released as the magnitude of an earthquake increases one unit, for example from magnitude 8 to 9. Why is the area so prone to earthquakes? The Pacific plate moves fast in tectonic terms, at a rate of 9cm (3. 5 inches) a year. This leads to the rapid buildup of huge amounts of energy. As the Pacific plate moves down, it sticks to the overhead plate and pulls it down too. Eventually, the join breaks, causing the seafloor to spring upwards several metres. The plate tectonics of the region are complex, and geologists are not sure which plate Japan sits on. Candidates include the Eurasian plate, the North American plate, the Okhotsk plate, and the Honshu microplate. How big were the waves? The largest waves measured by instruments in the water were 7 metres (nearly 23ft) high in the north-east of Japan, according to the Pacific Tsunami Warning Centre (PTWC) in Hawaii. Other estimates put the wave height at 10 metres. Waves reached 4 metres around the coast of Japan. As the tsunami spread across the Pacific, the wave height dropped to around 40cm in Guam and the nearby Marianas. The most powerful waves appeared to be moving south-west from Japan. Some countries may experience waves up to 2 metres, according to PTWC forecasts.

How much damage has been caused? Japan has invested heavily in coastal protection and buildings that can withstand tremors. Nevertheless, ports were pounded by the tsunami and the airport in Sendai was inundated. Nuclear power plants were shut down across the country and a state of emergency declared at the Fukushima nuclear power plant, where a cooling system failed. Modern buildings in Japan are designed to absorb the violent sideways shaking that can devastate cities. High-rise buildings can still be damaged, but are more likely to remain standing. There are concerns for low-lying islands in the Pacific. How long will the waves take to reach other countries? The tsunami moves across the Pacific at a speed of 500mph, with waves expected to reach the island of Fiji and Cairns in Australia at 3. 28pm GMT. From then, waves are due to reach Acapulco in Mexico at 7. 59pm, Chile at 10. 55pm, Ecuador at 11. 31pm, Colombia at 11. 47 and Peru at 12. 33am. Will there be aftershocks? Regular aftershocks have already hit Japan as the Earth's crust continues to rupture along the Japan trench. Those tremors are expected to be weaker and are less likely to produce another tsunami. The release of energy along the subduction zone between the Pacific and North Atlantic plates will transfer stress to other parts of the faultline, which could easily generate more earthquakes in the region in coming months.

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why does japan have so many natural disasters
why does japan have so many earthquakes and volcanoes
why does japan have so many earthquakes and tsunamis
why does japan have so many earthquakes
why does japan experience so many earthquakes and tsunamis
why does japan experience so many earthquakes
why does japan experience so many earthquakes