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Nazca Plate Region) GRENADA 80°W 60°W 40°W 11900900 a A' 1 1 1 2 0 200 400 600 800 1,000 1,200 BARBADOS Compiled by Gavin P

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Nazca Plate Region) GRENADA 80°W 60°W 40°W 11900900 a A' 1 1 1 2 0 200 400 600 800 1,000 1,200 BARBADOS Compiled by Gavin P U.S. DEPARTMENT OF THE INTERIOR OPEN-FILE REPORT 2015–1031-E U.S. GEOLOGICAL SURVEY This report supplements Open-File Report 2010–1083-E 80°W 70°W 60°W 50°W PRE-INSTRUMENTAL SEISMICITY 1500 – 1899 SAINT LUCIA Seismicity of the Earth 1900–2013 BARBADOS Deaths, tsunami, MMI VIII+, or M 8 SAINT VINCENT AND THE GRENADINES HONDURAS M 8.5 labeled with year ARUBA CURAÇAO Seismotectonics of South America (Nazca Plate Region) GRENADA 80°W 60°W 40°W 11900900 A A' 1 1 1 2 0 200 400 600 800 1,000 1,200 BARBADOS Compiled by Gavin P. Hayes, Gregory M. Smoczyk, Harley M. Benz, Antonio Villaseñor, TRINIDAD AND TOBAGO CURAÇAO NICARAGUA Barranquilla Maracaibo Caracas HONDURAS GRENADA 3 Valencia Maracay Demerara Plain and Kevin P. Furlong Cartagena TRENCH AXIS Managua Barquisimeto NICARAGUA 19921992 0 2014 11950950 Clark Basin 10° COSTA RICA PANAMA 1U.S. Geological Survey VENEZUELA 2 GUYANA Institute of Earth Sciences, Consejo Superior de Investigaciones Científicas, (CSIC), Barcelona, Spain COSTA RICA Panama FRENCH 3Department of Geosciences, Pennsylvania State University, University Park, Pa., USA San Jose Cucuta VENEZUELA SURINAME GUIANA 10°N 11983983 PANAMA –200 COLOMBIA Bucaramanga TECTONIC SUMMARY 19341934 GUYANA Equator The South American arc extends over 7,000 kilometers (km), from the Chilean margin triple junction offshore of southern Chile, to Medellin Equator ECUADOR its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate –400 Manizales FRENCH boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca Bogota SURINAME PROFILE A plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is Ibague GUIANA responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Cocos Ridge 11619619 Cali Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 COLOMBIA –600 PERU millimeters/year (mm/yr) in the south, to approximately 65 mm/yr in the north. Although the rate of subduction varies little along BRAZIL the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic 16871687 17161716 activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America. 11979979 15861586 1906 19581958 11513513 BOLIVIA Most of the large earthquakes in South America are constrained to shallow depths of 0–70 km as a result of both crustal and A Equator 18681868 19421942 18771877 interplate deformation. Crustal earthquakes are caused by deformation and mountain building in the overriding South America plate Quito 16041604 and generate earthquakes as deep as approximately 50 km. Interplate earthquakes occur due to slip along the dipping interface 11970970 AA'' Belem between the Nazca and the South America plates. Interplate earthquakes in this region are frequent and often large, and occur 20°S 20°S PARAGUAY between depths of approximately 10–60 km. Since 1900, numerous magnitude (M) 8 or larger earthquakes have occurred on this Equator ECUADOR Manaus Chile BB'Sao Luis subduction zone interface that were followed by devastating tsunamis, including the 1960 M9.5 earthquake in southern Chile, the Guayaquil 11906906 0 200 400 600 800 1,000 1,200 18191819 largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 19211921 TRENCH AXIS M8.5 earthquake near Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the 2001 M8.4 Arequipa, Peru 19531953 0 earthquake, the 2007 M8.0 earthquake near Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just north of the 1960 event. 17301730 18221822 URUGUAY Piura 22005005 Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in 90°W –200 ARGENTINA size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting 17511751 plate. These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern 19601960 Chiclayo Peru and southern Ecuador, with depths from 110 to 130 km. Most of these earthquakes occur adjacent to the bend in the coastline BB'' 15751575 PERU-CHILE TRENCH between Peru and Chile. The most recent large intermediate-depth earthquake in this region was the 2005 M7.8 Tarapaca, Chile, Trujillo –400 11963963 18371837 earthquake. PROFILE B 19701970 PERU 40°S 40°S Earthquakes can also be generated to depths greater than 600 km as a result of continued internal deformation of the subducting 19961996 19471947 Nazca plate. Deep-focus earthquakes in South America are not observed from a depth range of approximately 300–500 km. Instead, –600 deep earthquakes in this region occur at depths of 500–650 km and are concentrated into two zones: one that runs beneath the 11966966 11940940 BRAZIL FALKLAND ISLANDS Peru-Brazil border and another that extends from central Bolivia to central Argentina. These earthquakes generally do not exhibit (ISLAS MALVINAS) MAP EXPLANATION Callao 19741974 large magnitudes. An exception to this was the 1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake occurred Magnitude 10°S Lima –800 at a depth of 631 km, which was until recently was the largest deep-focus earthquake instrumentally recorded (superseded in May 8.0 19941994 20072007 Cuzco 19631963 2013 by a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was felt widely throughout South and North America. 1837 8.5 11908908 Subduction of the Nazca plate is geometrically complex and influences the geology and seismicity of the western edge of South America. The intermediate-depth regions of the subducting Nazca plate can be segmented into five sections based on their angle of Peru Basin 19961996 Cuiaba 100°W 80°W 60°W 40°W 20°W 19421942 subduction beneath the South America plate. Three segments are characterized by steeply dipping subduction; the other two by 11960960 Brasilia 0200 400 600 800 1,000 near-horizontal subduction. The Nazca plate beneath northern Ecuador, southern Peru to northern Chile, and southern Chile 2001 19221922 La Paz MILES B Arequipa descend into the mantle at angles of 25° to 30°. In contrast, the slab beneath southern Ecuador to central Peru, and under central Goiania 0200 400 600 800 1,000 19131913 Cochabamba BOLIVIA KILOMETERS Chile, is subducting at a shallow angle of approximately 10° or less. In these regions of “flat-slab” subduction, the Nazca plate 20012001 Santa Cruz de La Sierra moves horizontally for several hundred kilometers before continuing its descent into the mantle, and is shadowed by an extended zone of crustal seismicity in the overlying South America plate. Although the South America plate exhibits a chain of active volcanism resulting from the subduction and partial melting of the Nazca oceanic lithosphere along most of the arc, these regions of inferred shallow subduction correlate with an absence of volcanic activity. 22005005 SEISMIC HAZARD AND RELATIVE PLATE MOTION 19591959 Campo Grande Belo Horizonte Pacific Ocean 19761976 100°W 80°W 60°W 40°W The tectonics of the Antarctica triple junction in southern Chile (Chile triple junction), are controlled by the interactions of the 20°S CAYMAN ISLANDS HAITI DOMINICAN REPUBLIC FIGURE EXPLANATION Antarctica, South America, and Scotia plates. Immediately south of the Chile triple junction, the Antarctica plate subducts beneath PERU-CHILE TRENCH JAMAICA VIRGIN 10% in 50 year peak ground ISLANDS, U.S. acceleration South America at a rate of approximately 16 mm/yr. There have been no moderate-to-large earthquakes associated with this CHILE 20°N BELIZE GUADELOUPE 20°N 20072007 MEXICO 2 PARAGUAY GUATEMALA CARIBBEAN PLATE 0−0.2 m/s convergence over the past century. Moving south and east through Patagonia, plate motions between the South America and the HONDURAS SAINT LUCIA CURAÇAO 0.2−0.4 Scotia plates are predominantly left-lateral, at rates of 5–10 mm/yr. This plate boundary hosted two M7.8 earthquakes in December Chile Basin BARBADOS 20°S 11995995 Rio de Janeiro EL SALVADOR NICARAGUA 0.4−0.8 1949, near the Chile-Argentina border in Tierra del Fuego. Farther south, the Antarctica plate moves towards the east with respect 19501950 Niteroi Sao Paulo 0.8−1.6 PANAMA TRINIDAD AND to the Scotia plate at rates of less than 10 mm/yr, decreasing towards the south. Several M6–6.5 earthquakes have been observed in TOBAGO 1.6−3.2 Nazca Ridge 19871987 Santos the Drake Passage region over the past half-century, all with left-lateral strike-slip faulting mechanisms. Salta VENEZUELA 3.2−6.4 Asuncion GUYANA 6.4−9.8 FRENCH 19661966 Curitiba COCOS PLATE COLOMBIA SURINAME DATA SOURCES CC' 6655 mmm/yrm/yr GUIANA Relative plate motion –200 0 200 400 600 800 1,000 5588 mmm/yrm/yr 7−20 mm/yr 19831983 The earthquakes portrayed on the main map and the depth profiles are taken from two sources: (a) the Centennial earthquake TRENCH AXIS San Miguel De Tucuman 21−40 catalog (Engdahl and Villaseñor, 2002) and annual supplements for the interval 1900–2007, where the magnitude floor is 5.5 ECUADOR C 19181918 CC'' Santos Equator 41−60 globally, and (b) a catalog of earthquakes having high-quality depth determinations for the period 1964–2002 and a magnitude Equator Plateau range of 5.0–5.4 (Engdahl, written commun., 2003) 0 61−80 1922 Sala y Gomez Ridge SOUTH AMERICA 11918918 The nucleation points of great earthquakes larger than M8.3 are designated with a label showing the year of occurrence.
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