Nightly News   |  February 27, 2010

Haiti, Chile quakes connected?

NBC’s Robert Bazell examines the science of underwater earthquakes and tsunamis.

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This content comes from Closed Captioning that was broadcast along with this program.

>> wish you continued safe journeys.

>>> today's massive earthquake followed the 7.0 quake in haiti just last month, and others recently around the globe leave us wondering there is a pattern and more trouble ahead. we get some answers from nbc news's chief science correspondent robert bazell .

>> reporter: chile today. haiti last month. when deadly earthquakes appear one after another, people always ask, is there a connection?

>> this is a very, very --

>> reporter: seismologist say no, there are earthquakes all the time.

>> this sense that we're having a lot of big ones close together, these are not related, they involve different pairs of plates.

>> reporter: plates, huge sections of the earth's crust that are in constant motion . the boundaries where they meet are called faults, and when enough pressure builds, the fault slips violently causing an earthquake . at the site of today's place, the nazca plate is pushing under the south american plate . it's known as the ring of fire . today's earthquake was just 150 miles north of the biggest earthquake ever recorded, magnitude 9.5 and sent huge tsunamis around the pacific. the numbers used to measure an earthquake 's magnitude don't tell the whole story. today's quake was far more powerful than the one that struck haiti january 12th .

>> it would produce about 500 times as much energy as a magnitude 7. this is a much larger quake.

>> reporter: everyone expects the death toll in chile to climb, it will fall far short of the number killed in haiti , where the earthquake struck right beneath a densely populated , poorly built area.

>> the center in today's quake is further from populated areas than in haiti . the shaking felt in populated areas is less.

>> reporter: when an earthquake strikes under the ocean, a tsunami occurs when the ruptured fault moves violently up or down. today's quake moved 350 miles of ocean floor , displacing so much water that scientists predicted the waves would travel as far as japan and russia. robert bazell , nbc news, new york.