EXPLORING THE EARTH: Earthquake in Ecuador

(EXPLORING THE EARTH is a regular column that examines various aspects of Earth Science through the lens of The Layered Earth software.  This newsletter examines the recent massive earthquake that occurred in Ecuador and how The Layered Earth software can be used to illustrate several unique features relating to this geological event.)

The earthquake’s epicenter was near the Pacific coast of Ecuador.

A massive earthquake of magnitude 7.8 struck Ecuador on April 16, 2016.  The earthquake occurred in the early evening at 6:58 p.m. local time (23:58 UTC), and was located near the Pacific coast approximately 170 km (106 miles) west of the capital city of Quito.  The earthquake occurred at a relatively shallow depth of 19.2 km (11.9 mi) and was powerful enough to cause widespread damage that resulted in the death of approximately 577 people.

These two photos provide graphic evidence of the widespread damage caused by the Ecuador earthquake.

Ecuador is an extremely active seismic zone since it lies above the boundary where two large tectonic plates meet; the Nazca Plate and the South American Plate. 

The Nazca and the South American plates meet off the Pacific coast of South America.

Layered Earth software users:  To view tectonic plates:

  • Click on the Layers button in the bottom left corner of the screen.
  •  Navigate through the following subdirectories by clicking on the subdirectory symbol  beside each subdirectory name:

o   PLATE TECTONICS -> TECTONIC PLATES (make sure that you have clicked on the check box beside TECTONIC PLATES). 

  • A number of subdirectories will now be visible.  Uncheck the box beside COMPOSITE MAP (it is the default).  Click on the check box beside TECTONIC PLATE OUTLINES.  You will now see an outline of the tectonic plates on the main screen.
  • Now also click on the check box for TECTONIC PLATES (SHADED).  This will serve to color in all of the tectonic plates making them more visible.
  • Now click on the subdirectory symbol  immediately to the left of the check box for TECTONIC PLATES (SHADED).  A listing of all the tectonic plates now appears.  Uncheck all of the boxes except for Nazca Plate and South American Plate.  Now only the Nazca and South American plates will be highlighted and colored in.

(Note:  Users may wish to turn off the cloud layer as this can sometimes obscure the underlying data layer.  Click on the subdirectory symbol  beside the ATMOSPHERE AND STARS subdirectory in Layers.  Uncheck the box beside Clouds.

The ongoing interaction between these two plates has resulted in Ecuador experiencing numerous strong earthquakes including a magnitude 8.2 earthquake on Dec. 12, 1979 (300-600 deaths), and an 8.8 magnitude earthquake on January 31, 1906 (approximately 1,000 deaths). 

The entire interface between the Nazca Plate and the South American Plate is an active seismic zone.

Layered Earth software users:  To view the Earthquake data layer (along with tectonic plate outlines):

  •  Click on the subdirectory symbol  to the left of EARTHQUAKES in the Layers tab.
  • Click on the check box beside USGS Historical Earthquakes.  You will now see a global view of all earthquakes since 1900.  Shallow depth earthquakes (0-70 km/0-44 miles) are marked by red dots, intermediate depth earthquakes (70-300 km/44-186 miles) are marked by yellow dots, and deep earthquakes (greater than 300 km/186 miles) are marked by green dots.
  • Clicking on the Settings... button to the right brings up a small screen with sliders that allows you to manipulate the kind of earthquake data that is visible on the screen.
  • To add in the tectonic plate outlines:  Navigate through the following subdirectories:  PLATE TECTONICS -> TECTONIC PLATES (make sure that you have clicked on the check box beside TECTONIC PLATES).  Uncheck the box beside COMPOSITE MAP (it is the default) and click on the check box beside TECTONIC PLATE OUTLINES.

The Settings... button allows you to control the depth, magnitude, and date of Earthquake data.

Earthquakes in this region are produced as a result of the Nazca Plate, a heavy oceanic plate, sliding under the South American Plate, a lighter continental plate.  This process, where one tectonic plate slides under another one, is known as subduction.  The Nazca Plate is slowly being subducted eastward under the South American Plate at a rate of 61 mm/year (2.1 in/year).  

Vectors and color are used to represent plate velocities.

Layered Earth software users:  To view the Plate Velocity data layer

  •  Navigate through the following subdirectories in the Layers tab by clicking on the subdirectory symbol  beside each subdirectory name:

o   PLATE TECTONICS -> TECTONIC PLATES (make sure that you have clicked on the check box beside TECTONIC PLATES).

Uncheck the box beside COMPOSITE MAP (it is the default) and click on the check box beside PLATE VELOCITY.

Stress builds up over time between the two plates as they slowly grind against one another.  Eventually the stress and strain between the two plates reaches such a level that the rock will fracture and the two plates will suddenly “slip” past one another resulting in an earthquake.  It was just such an event, known as a megathrust event, that occurred in Ecuador on April 16, 2016.

A high degree of strain is evident along the interface between the Nazca and the South American plates.

Layered Earth software users:  To view the Plate Velocity data layer

  • Navigate through the following subdirectories in the Layers tab by clicking on the subdirectory symbol  beside each subdirectory name:

o   PLATE TECTONICS -> TECTONIC PLATES (make sure that you have clicked on the check box beside TECTONIC PLATES).

Uncheck the box beside COMPOSITE MAP (it is the default) and click on the check box beside GLOBAL STRAIN RATE.    

The subduction zone between the Nazca and the South American plates has resulted in the formation of a deep oceanic trench off the coast of South America.  The Ecuador Trench has a maximum depth of approximately 3.0 km (1.9 miles).

The Ecuador Trench marks the subduction zone between the Nazca and the South American plates.

Reference Files:

Ready access to all of the views and data sets that have been mentioned in this article is available if you own The Layered Earth software.  Each file (after it has been downloaded) can be viewed by clicking File/Open in the upper menu bar, and then following the path to its location.