By Jason DeRusha

By Jason DeRusha, WCCO-TV

MINNEAPOLIS (WCCO)Since the earthquake and tsunami hit in Japan, WCCO viewers have been sending in dozens of Good Questions. Jason DeRusha hits reply all.

– How does a tsunami start? – Joey Stepnick

“A tsunami starts when there’s a very specific type of earthquake,” said WCCO Meteorologist Mike Augustyniak. “It’s when one tectonic plate … goes under another in a real jerky motion.”

That sends ocean water out of whack as it tries to find equilibrium. Huge waves start moving at 400 and 500 miles per hour — faster than an airplane.

“In the middle of the ocean, where there’s 10,000 feet of water beneath you. … It’s really energy that’s traveling through the water,” said Augustyniak.

By the time those walls of water hit the shore, they’re slowed to more like 40 miles per hour.

“All of that energy from the wave has to go somewhere. It can’t burrow into the ground so it actually lifts the water up and creates the wave,” said Augustyniak.

-Why does the water pull back from the shore? – Denise in Hudson

“That’s the water actually gathering to make the tsunami wave,” said Augustyniak.

It’s like dropping a boulder in a swimming pool. Before the waves crash over the edge, the water gets pulled towards the center.

-Is there a difference between tsunami and tidal wave? – Bob Moffit

Tidal wave is the colloquial term for tsunami. But it’s not accurate because the tides have nothing to do with a tsunami. That’s why in 1963 the scientific community stopped calling it a tidal wave. Tsunami literally means harbor wave in Japanese.

-If an earthquake hit in Lake Superior, could there be a tsunami? – Craig in Lino Lakes

The answer is yes, and it actually could be more devastating than in an ocean. That’s because in Lake Superior, it would trigger underwater landslides which could send incredible waves hurdling towards the shore.

Comments (8)
  1. Ben Chorn says:

    There are no active faults in Lake Superior so there is no possible way of getting a tsunami. There are also no mountains to have land-slide tsunamis. Check your science.

    1. Carolyn S. says:

      The statement was “if an earthquake….”, so it was a theoretical question. Check your grammar.

      There actually is fault line activity in Minnesota, and while it’s not of the same enormity as along the Pacific Rim, there were several quakes reported in the last 20 years. Check your science.

  2. St Paul says:

    Could the dead fish that came to shore in CA have been a precurser to the earthquake and after affects?

  3. Rita says:

    Many larger-scale earthquakes seem to happen during the day. Is there any scientific explanation for this?

  4. Margaret says:

    So my question is about is about the nuclear reactor. If it explodes what areas would be effected by radiation? Should we (as in people in MN,WI,IA…etc) be taking precautions also?

  5. Siryka H. says:

    If US ships are being pulled further from Japan due to radiation then why are Japanese citizens not being evacuated?

  6. larry k says:

    what, if any effect does radiation have on water such as an ocean?

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