1. South America EQ Report, Week 2
January 26, 2016
Olivia helprin

2. 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, Web. 26 Jan <

3. 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 <

4. This Week in Seismic News…
According to the ANSS Catalog, there have been a series of 19 earthquakes with magnitudes ranging between 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 to degrees longitude and to degrees latitude).
The largest earthquakes, with magnitudes of 5.00, occurred on January 19th and 20th within similar localities:
January 19th: ( , ), km deep
January 20th: ( , ), km deep

5. Sources
"ANSS Catalog Search." ANSS Catalog Search. Northern California Earthquake Data Center, n.d. Web. 26 Jan
"Seismotectonics of South America (Nazca Plate Region)." Seismicity of the Earth 1900–2013. US Geologic Survey, Web. 26 Jan <
Lewis, Steve. "Offshore Earthquakes and Landslides." SOPAC. USGS, n.d. Web. 26 Jan <
"South America - Earthquakes and Tectonics." IRIS -. N.p., n.d. Web. 26 Jan <
"Chile Margin and Triple Junction Geology." NOAA Ocean Explorer Podcast RSS. N.p., n.d. Web. 26 Jan < ology.html>.