The 8.8 magnitude earthquake was the largest of many earthquakes that occur along the coast of Chile between the Nazca and South American tectonic plates.  As you can see on the map here, earthquakes regularly happen here, and around the rim of the Pacific (the Rim of Fire).  The 8.8 magnitude quake was a deep one, about 21 miles below the surface, reflecting the movement of the Nazca plate eastward under the South American plate.

Map of earthquakes including quakes along the coast of Chile, and around the Pacific. Click on the map to see the map of real-time quakes.

The 8.8 quake, deep below the ocean, released enormous energy that resulted in the displacement of a very large volume of water causing a tsunami.   The earthquakes along the coast of Chile are the result on the convergence of two plates, and in this case, deep below the ocean.  Tsunami would be expected when such an earthquake occurs.  The tsunami that was generated by the February 27th 8.8 earthquake traveled across the Pacific Ocean as far as Japan and Russia.  Many of us watch TV images as the tsunami made its way to Hawaiian Islands, and although arriving at the expected time, the tsunami fortunately was not as big as was expected.  Here is a map showing the generation and movement of the tsunami across the Pacific provided by the Earthquake Research Institute, University of Tokyo.

The map shows an animation of the movement of tsunami across the Pacific.

Tsunami model created by the Earthquake Research Institute, Tokyo.