The February 27, 8.8 earthquake offshore Maule, Chile occurred at the boundary between the Nazca and the South American Plates.  According to reports from the USGS, coastal Chile has been the location of vary large earthquakes for centuries.  There has been a written record of earthquakes in Chile since the 16th Century.  In 1735, when Charles Darwin, aboard the Beagle, experienced a devastating earthquake in Chile, and not only wrote about the experience, but visited damaged towns to witness the destruction caused by that quake.

February 28, 8.8 earthquake map

The 8.8 earthquake has caused enormous damage in many cities and town in Chile, and the tsunami generated by the quake caused the destruction of coastal towns.  More than 150 aftershocks of greater magnitude than 5.0 have occurred, and will continue into the near future.

Chile is located along the boundary of two tectonic plates, the Nazca plate, and the South American plate.  The Nazca plate is moving about 70mm per year eastward under the South American plate.  You can get an idea of the seismic activity in the area by observing the location and depth of earthquake along a line that runs west to east across the Nazca and South American plates.  The map below shows a profile along the line A – A’.  As you move from A toward A’ the depth of the earthquakes increase (deepest shown in dark blue).  The 8.8 earthquake is represented by the star in the yellow zone.  It was 21.7 miles deep.

Seismicity cross section and map of earthquake in Chile

The historical record for the observation of earthquakes along the coast of Chile, as mentioned above, goes back to the 16 Century.  The USGS reports the seismic activity in the region this way:

USGS map of historical record of earthquakes in Chile

Since the middle of the 16th century, there is a comprehensive written record of other large damaging earthquakes throughout the region. Notable mega-thrust earthquakes prior to 1900 include earthquakes in 1868 and 1877 offshore southern Peru and northern Chile. In the vicinity of the 2010 earthquake, damaging earthquakes were reported in 1751, near Concepcion, and one further to the north in 1730. Tsunamis from the 1730, 1751, 1868, and 1877 earthquakes produced Pacific-wide tsunamis as evidenced from detailed records of flooding and damage in Japan. An 1835 Concepcion earthquake is notable because the great explorers Charles Darwin and Robert FitzRoy provided observations and comments.

The USGS expects that the aftershocks will continue, and as of today 142 aftershocks greater than magnitude 5 have been reported, and of these 10 have been greater than magnitude 6.