Three earthquakes that jolted central Japan this week are not indicators of much-expected colossal temblors Japanese have already named, experts said Thursday.

The three quakes were the result of cracks occurring within the plates under Japan, not by tectonic deformation caused by plate movement, which is expected to cause a massive quake at some point in the future, said Tomoaki Ozaki, assistant chief of the Japan Meteorological Agency’s Earthquake and Tsunami Observation Division.

A magnitude 6.6 quake Thursday morning originated 35 miles below the surface of Hachijo Island near Tokyo, according to the meteorological agency.

On Tuesday, a magnitude 6.5 temblor hit Shizukoka Prefecture southwest of Tokyo, killing a 43-year-old woman who was buried under books that fell from bookshelves in her apartment. A total of 122 people were injured and 5,192 homes were damaged, according to Japan’s Fire and Disaster Management Agency. On Sunday, a magnitude 6.8 quake originated deep under the water off Shizuoka.

While Ozaki said the three quakes likely are not indicators of a bigger one to come, neither did they relieve tectonic plate pressure that could delay a catastrophic quake.

“The jolt does not mean that the pressure, meaning the seismic energy that has been accumulated, was let out,” he said.

The expected great Tokai Earthquake and the Metropolitan Epicentral Earthquake, named for their likely locales in the greater Kanto region of Tokyo, could happen any day and at any time, he said. For more than three decades, earthquake experts and government officials have been predicting and preparing for such catastrophic quakes in central Japan.

Takeshi Matsumoto, professor of marine geophysics at the University of the Ryukyus, said that earthquake occurred in Shizuoka on Tuesday released one-thirtieth of the energy of the expected Tokai Earthquake.

In Tokyo, the last major killer earthquake occurred in 1923. The Great Kanto Earthquake, with a magnitude 7.9, claimed more than 140,000 lives and damaged and burned more than 680,000 homes and buildings.

Elsewhere in Japan, the last catastrophic quake was the magnitude 7.2 Great Hanshin Awaji Earthquake in 1995, which killed more than 6,400 people and injured nearly 44,000 people in the Kobe area. The quake and subsequent fires destroyed more than 527,000 homes and buildings.

But no place in Japan is safe from an earthquake.

The Kanto region sits atop three plates — the inland, Philippine and Pacific — which are intricately interlaced, Ozaki said.

“Noticeable seismic tremors happen at least once every day somewhere in Japan’s archipelago,” Ozaki said.

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