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South America EQ
Report, Week 2
JANUARY 26, 2016
OLIVIA HELPRIN
Map of South America’s Seismicity and
Plate Boundaries
Source: "Seismotectonics of South
America (Nazca Plate Region)." Seismicity
of the Earth 1900–2013. US Geologic
Survey, 2014. Web. 26 Jan. 2016.
<http://pubs.usgs.gov/of/2015/1031/e/pdf
/of2015-1031-E.pdf>.
Background of South America’s
Plate Boundaries


Subduction of the Nazca plate:

The South America plate’s west margin overrides the Nazca
plate, forming a convergent plate boundary. According to
the USGS, “the Nazca plate moves slightly north of eastwards
at a rate varying from approximately 80mm/yr in the south,
to approximately 65 mm/yr in the north.”

This subduction is responsible for the majority of the tectonic
activity experienced in South America. In addition to shallow
(0–70 km), intermediate (70-300km) and great (~600km)
depth earthquakes, active volcanic chains are present
along South America’s west coast due to the melting of the
Nazca plate’s lithosphere in locations of intermediate to
great depth subduction.
Chilean Triple Junction:

This region “represents the only presently active ridge-trench
collision where the overriding plate is composed of
continental lithosphere” (Lewis).

This is the site of the largest earthquake ever recorded, with
a 9.8 magnitude in 1960.
Source: Lewis, Steve. "Offshore Earthquakes and Landslides."
SOPAC. USGS, n.d. Web. 26 Jan. 2016.
<https://walrus.wr.usgs.gov/earthquakes/sopac.html>.
This Week in Seismic News…

According to the ANSS Catalog, there have been a series of 19
earthquakes with magnitudes ranging between 4.00 - 5.00 within the
last week (1/19-26/2016).

These earthquakes range from 7 – 205 km deep. All occurred along
the north-central western coast of South America (between -68.5009
to -88.8323 degrees longitude and 6.8073 to -32.6255 degrees
latitude).

The largest earthquakes, with magnitudes of 5.00, occurred on
January 19th and 20th within similar localities:

January 19th: (-14.0753, -72.8806), 48.17 km deep

January 20th: (-15.8792, -74.0797), 47.03 km deep
Sources

"ANSS Catalog Search." ANSS Catalog Search. Northern California Earthquake
Data Center, n.d. Web. 26 Jan. 2016.

"Seismotectonics of South America (Nazca Plate Region)." Seismicity of the Earth
1900–2013. US Geologic Survey, 2014. Web. 26 Jan. 2016.
<http://pubs.usgs.gov/of/2015/1031/e/pdf/of2015-1031-E.pdf>.

Lewis, Steve. "Offshore Earthquakes and Landslides." SOPAC. USGS, n.d. Web. 26
Jan. 2016. <https://walrus.wr.usgs.gov/earthquakes/sopac.html>.

"South America - Earthquakes and Tectonics." IRIS -. N.p., n.d. Web. 26 Jan. 2016.
<https://www.iris.edu/hq/programs/education_and_outreach/animations/35>.

"Chile Margin and Triple Junction Geology." NOAA Ocean Explorer Podcast RSS.
N.p., n.d. Web. 26 Jan. 2016.
<http://oceanexplorer.noaa.gov/explorations/10chile/background/geology/ge
ology.html>.