February 9, 2016 - CHILE - A strong earthquake with a preliminary magnitude of 6.3 has struck off the coast of central Chile, centered off Tongoy and La Serena, seismologists say. No tsunami warnings have been issued.
The earthquake, which struck at 9:33 p.m. local time on Tuesday, was
centered in the ocean about 48 kilometers southwest of the coastal town
of Tongoy, or 89 kilometers southwest of La Serena. It struck about 19
kilometers deep, making it a shallow earthquake, according to Chile's
national seismological agency.
USGS shakemap intensity.
Moderate shaking was felt in the Coquimbo Region, according to Chile's
National Office of Emergency of the Interior Ministry (ONEMI). "The
characteristics of the earthquake do not meet the conditions necessary
to generate a tsunami off the coast of Chile," ONEMI said in an alert.
No tsunami warnings have been issued.
Citizens on the streets of La Serena. In some
localities power outages were reported , but no major damage has been
reported so far
Other details were not yet available, but there were no immediate reports of damage or casualties.
Chile and the wider region are on the so-called 'Pacific Ring of Fire'
which is regularly struck by large earthquakes, including the Great
Chilean earthquake that struck the coast of central Chile on May 22,
1960. The 9.5-magnitude earthquake, the largest earthquake ever
instrumentally recorded, left between 490 and 5,700 people killed.
- BNO News.
Seismotectonics of South America (Nazca Plate Region)
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
November 10, 2015 - CHILE - A 6.9 magnitude earthquake has struck off the coast of Chile, some 100 kilometers west of Coquimbo, according to USGS.
The epicenter of the
earthquake was located at a depth of just 10 kilometers (6.2 miles),
according to the United States Geological Survey, which initially
reported it as having a magnitude 6.6.
The Pacific Tsunami Warning Center said that based on all available data they have received, there is no threat of a tsunami.
There were no immediate reports of any injuries or damage having
occurred to local buildings. Chile’s Navy confirmed that the parameters
of the quake did not suggest a possible threat of a tsunami occurring.
USGS earthquake shakemap intensity map.
The
quake affected the same region as the deadly 8.3-magnitude earthquake
in September, which killed at least 15 and forced over one million
people to evacuate their homes, triggering tsunami warnings in
California and Hawaii.
Chile
has a long history of major quakes, including the strongest recorded in
recent history. At least 1,655 people were killed and 3,000 injured in
the Great Chilean Earthquake of 1960. - RT.
Seismotectonics of South America (Nazca Plate Region).
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
March 28, 2015 - CHILE - A 6.0-magnitude earthquake struck northern Chile today, but there was no immediate word of any injuries or damage.
The
earthquake struck at 16:36:52 UTC – at a depth of 109.3km, 40km
northeast of Calama, near Chile’s border with Bolivia, according to the
United States Geological Survey.
USGS shakemap intensity
Chile is one of the world's
most seismic countries and is prone to tsunamis because of the way the
Nazca tectonic plate plunges beneath the South American plate, pushing
the towering Andes cordillera ever higher.
Tectonic Summary - Seismotectonics of South America (Nazca Plate Region)
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
USGS plate tectonics for the region
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
Large intermediate-depth earthquakes
(those occurring between depths of approximately 70 and 300 km) are
relatively limited in size and spatial extent in South America, and
occur within the Nazca plate as a result of internal deformation within
the subducting plate. These earthquakes generally cluster beneath
northern Chile and southwestern Bolivia, and to a lesser extent beneath
northern Peru and southern Ecuador, with depths between 110 and 130 km.
Most of these earthquakes occur adjacent to the bend in the coastline
between Peru and Chile. The most recent large intermediate-depth
earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.
Earthquakes
can also be generated to depths greater than 600 km as a result of
continued internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, which was until recently the largest
deep-focus earthquake instrumentally recorded (superseded in May 2013 by
a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was
felt widely throughout South and North America.
Subduction of the
Nazca plate is geometrically complex and impacts 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 subduction beneath the South America
plate. Three segments are characterized by steeply dipping subduction;
the other two by near-horizontal subduction. The Nazca plate beneath
northern Ecuador, southern Peru to northern Chile, and southern Chile
descend into the mantle at angles of 25° to 30°. In contrast, the slab
beneath southern Ecuador to central Peru, and under central Chile, is
subducting at a shallow angle of approximately 10° or less. In these
regions of “flat-slab” subduction, the Nazca plate 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. More information on regional seismicity and tectonics
March 23, 2015 - CHILE - A 6.4-magnitude earthquake struck northern Chile today, and there was no immediate word of any injuries or damage.
USGS earthquake location
The
earthquake struck at 1:51 a.m. local time – at a depth of 75 miles –
about 30 miles southeast of Putre, near Chile’s border with Bolivia, according to the United States Geological Survey.
USGS shakemap intensity
Chile
is one of the world's most seismic countries and is prone to tsunamis
because of the way the Nazca tectonic plate plunges beneath the South American plate, pushing the towering Andes cordillera ever higher. - ABC News.
Tectonic Summary - Seismotectonics of South America (Nazca Plate Region)
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
USGS plate tectonics for the region
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
Large intermediate-depth earthquakes
(those occurring between depths of approximately 70 and 300 km) are
relatively limited in size and spatial extent in South America, and
occur within the Nazca plate as a result of internal deformation within
the subducting plate. These earthquakes generally cluster beneath
northern Chile and southwestern Bolivia, and to a lesser extent beneath
northern Peru and southern Ecuador, with depths between 110 and 130 km.
Most of these earthquakes occur adjacent to the bend in the coastline
between Peru and Chile. The most recent large intermediate-depth
earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.
Earthquakes
can also be generated to depths greater than 600 km as a result of
continued internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, which was until recently the largest
deep-focus earthquake instrumentally recorded (superseded in May 2013 by
a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was
felt widely throughout South and North America.
Subduction of the
Nazca plate is geometrically complex and impacts 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 subduction beneath the South America
plate. Three segments are characterized by steeply dipping subduction;
the other two by near-horizontal subduction. The Nazca plate beneath
northern Ecuador, southern Peru to northern Chile, and southern Chile
descend into the mantle at angles of 25° to 30°. In contrast, the slab
beneath southern Ecuador to central Peru, and under central Chile, is
subducting at a shallow angle of approximately 10° or less. In these
regions of “flat-slab” subduction, the Nazca plate 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. More information on regional seismicity and tectonics
February 11, 2015 - ARGENTINA - A strong but deep earthquake has struck northern Argentina, but there are no immediate reports of damage.
USGS earthquake location - satellite imagery
The 6.7-magnitude earthquake struck northeastern of the Chile border on Wednesday, the US Geological Survey said.
The
quake, initially reported as a major 7.0, was fairly deep at 252
kilometres below the earth, which should lessen its impact. Its
epicentre was located 178 kilometres northwest of the Argentine town of
Jujuy.
USGS shakemap intensity
According to the Pacific Tsunami Warning Center, it was
not strong enough to generate a tsunami threat to countries along the
Pacific Ring of Fire.
Tectonic Summary - Seismotectonics of South America (Nazca Plate Region)
The South American arc extends over 7,000 km, from the Chilean margin triple junction offshore of southern Chile to its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 65 mm/yr in the north. Although the rate of subduction varies little along the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America.
Most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 km resulting from both crustal and interplate deformation. Crustal earthquakes result from deformation and mountain building in the overriding South America plate and generate earthquakes as deep as approximately 50 km. Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates. Interplate earthquakes in this region are frequent and often large, and occur between the depths of approximately 10 and 60 km. Since 1900, numerous magnitude 8 or larger earthquakes have occurred on this subduction zone interface that were followed by devastating tsunamis, including the 1960 M9.5 earthquake in southern Chile, the largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 M8.5 earthquake near Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the 2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just north of the 1960 event.
USGS plate tectonics for the region
Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting plate. These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern Peru and southern Ecuador, with depths between 110 and 130 km. Most of these earthquakes occur adjacent to the bend in the coastline between Peru and Chile. The most recent large intermediate-depth earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.
Earthquakes can also be generated to depths greater than 600 km as a result of continued internal deformation of the subducting Nazca plate. Deep-focus earthquakes in South America are not observed from a depth range of approximately 300 to 500 km. Instead, deep earthquakes in this region occur at depths of 500 to 650 km and are concentrated into two zones: one that runs beneath the Peru-Brazil border and another that extends from central Bolivia to central Argentina. These earthquakes generally do not exhibit large magnitudes. An exception to this was the 1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake occurred at a depth of 631 km, which was until recently the largest deep-focus earthquake instrumentally recorded (superseded in May 2013 by a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was felt widely throughout South and North America.
Subduction of the Nazca plate is geometrically complex and impacts 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 subduction beneath the South America plate. Three segments are characterized by steeply dipping subduction; the other two by near-horizontal subduction. The Nazca plate beneath northern Ecuador, southern Peru to northern Chile, and southern Chile descend into the mantle at angles of 25° to 30°. In contrast, the slab beneath southern Ecuador to central Peru, and under central Chile, is subducting at a shallow angle of approximately 10° or less. In these regions of “flat-slab” subduction, the Nazca plate 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.
February 2, 2015 - ARGENTINA - An earthquake with a magnitude of 6.3 rattled northwestern Argentina on Monday, the U.S. Geological Survey said, but there were no immediate reports of casualties.
The quake struck 93 km (58 miles) northwest of San Luis, which lies in the shadow of the Andes mountains, at a depth of 184 kilometers, USGS data showed.
USGS shakemap intensity.
Local journalist Alejandro Costanzo said that while the tremors did not feel strong in the city, they lasted a long time. He said he had seen no immediate signs of damage in San Luis.
"Buildings here are designed for this kind of event," Costanzo told television station TN from San Luis, adding that the surrounding region was lightly populated. - Reuters.
Tectonic Summary - Seismotectonics of South America (Nazca Plate Region)
The South American arc extends over 7,000 km, from the Chilean margin triple junction offshore of southern Chile to its intersection with the Panama fracture zone, offshore of the southern coast of Panama in Central America. It marks the plate boundary between the subducting Nazca plate and the South America plate, where the oceanic crust and lithosphere of the Nazca plate begin their descent into the mantle beneath South America. The convergence associated with this subduction process is responsible for the uplift of the Andes Mountains, and for the active volcanic chain present along much of this deformation front. Relative to a fixed South America plate, the Nazca plate moves slightly north of eastwards at a rate varying from approximately 80 mm/yr in the south to approximately 65 mm/yr in the north. Although the rate of subduction varies little along the entire arc, there are complex changes in the geologic processes along the subduction zone that dramatically influence volcanic activity, crustal deformation, earthquake generation and occurrence all along the western edge of South America.
Most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 km resulting from both crustal and interplate deformation. Crustal earthquakes result from deformation and mountain building in the overriding South America plate and generate earthquakes as deep as approximately 50 km. Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates. Interplate earthquakes in this region are frequent and often large, and occur between the depths of approximately 10 and 60 km. Since 1900, numerous magnitude 8 or larger earthquakes have occurred on this subduction zone interface that were followed by devastating tsunamis, including the 1960 M9.5 earthquake in southern Chile, the largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 M8.5 earthquake near Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the 2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just north of the 1960 event.
USGS plate tectonics.
Large intermediate-depth earthquakes (those occurring between depths of approximately 70 and 300 km) are relatively limited in size and spatial extent in South America, and occur within the Nazca plate as a result of internal deformation within the subducting plate. These earthquakes generally cluster beneath northern Chile and southwestern Bolivia, and to a lesser extent beneath northern Peru and southern Ecuador, with depths between 110 and 130 km. Most of these earthquakes occur adjacent to the bend in the coastline between Peru and Chile. The most recent large intermediate-depth earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.
Earthquakes can also be generated to depths greater than 600 km as a result of continued internal deformation of the subducting Nazca plate. Deep-focus earthquakes in South America are not observed from a depth range of approximately 300 to 500 km. Instead, deep earthquakes in this region occur at depths of 500 to 650 km and are concentrated into two zones: one that runs beneath the Peru-Brazil border and another that extends from central Bolivia to central Argentina. These earthquakes generally do not exhibit large magnitudes. An exception to this was the 1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake occurred at a depth of 631 km, which was until recently the largest deep-focus earthquake instrumentally recorded (superseded in May 2013 by a M8.3 earthquake 610 km beneath the Sea of Okhotsk, Russia), and was felt widely throughout South and North America.
Subduction of the Nazca plate is geometrically complex and impacts 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 subduction beneath the South America plate. Three segments are characterized by steeply dipping subduction; the other two by near-horizontal subduction. The Nazca plate beneath northern Ecuador, southern Peru to northern Chile, and southern Chile descend into the mantle at angles of 25° to 30°. In contrast, the slab beneath southern Ecuador to central Peru, and under central Chile, is subducting at a shallow angle of approximately 10° or less. In these regions of “flat-slab” subduction, the Nazca plate 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. - USGS.
November 2, 2014 - EASTER ISLAND REGION, PACIFIC OCEAN - A
strong earthquake jolted the southeastern Pacific on Saturday, about
544 kilometers (338 miles) south-southeast of Chile's Easter Island, the
US Geological Survey said.
The 6.0-magnitude quake, which hit at 3:59 am local time (10:59 GMT), registered at a depth of 10 kilometers (6.2 miles).
It did not immediately spark a tsunami warning, according to the Hawaii-based Pacific Tsunami Warning Center.
USGS earthquake shakemap intensity
Chile is one of the most seismically active countries in the world, and
is located in the so-called Ring of Fire area of the Pacific Ocean
basin.
Last month, a 7.2-magnitude quake struck some 570 kilometers south of Easter Island.
Seismotectonics of South America (Nazca Plate Region)
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most of the large earthquakes in South America are constrained to
shallow depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large intermediate-depth earthquakes
(those occurring between depths of approximately 70 and 300 km) are
relatively limited in size and spatial extent in South America, and
occur within the Nazca plate as a result of internal deformation within
the subducting plate. These earthquakes generally cluster beneath
northern Chile and southwestern Bolivia, and to a lesser extent beneath
northern Peru and southern Ecuador, with depths between 110 and 130 km.
Most of these earthquakes occur adjacent to the bend in the coastline
between Peru and Chile. The most recent large intermediate-depth
earthquake in this region was the 2005 M7.8 Tarapaca, Chile earthquake.
Earthquakes can also be generated to depths greater than 600 km as a
result of continued internal deformation of the subducting Nazca plate.
Deep-focus earthquakes in South America are not observed from a depth
range of approximately 300 to 500 km. Instead, deep earthquakes in this
region occur at depths of 500 to 650 km and are concentrated into two
zones: one that runs beneath the Peru-Brazil border and another that
extends from central Bolivia to central Argentina. These earthquakes
generally do not exhibit large magnitudes. An exception to this was the
1994 Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
May 06, 2014 - CHILE - A strong magnitude 6.1 earthquake hit west of the Chile Rise, on Tuesday at 20:52:26 UTC, the U.S. Geological Survey and local officials said.
There were no reports of serious damage to Chile or any structure on the South American mainland.
USGS earthquake location.
The quake, initially reported as a magnitude 6.5, struck at a depth of 6.2 miles, 975 miles southeast of Easter Island, Chile; and 1,280 miles west of Lebu, Chile.
The navy said the quake did not meet the conditions needed to generate a tsunami off the country's Pacific coastline.
Nearly four years ago, a massive 8.8-magnitude earthquake and ensuing tsunami ravaged central-southern Chile, killing hundreds of people and causing billions of dollars worth of damage.
Seismotectonics of South America (Nazca Plate Region).
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
April 10, 2014 - CHILE - A 6.0 magnitude earthquake has struck Chile, says the US Geological Survey.
USGS earthquake location map.
The epicenter of tremor was located 84 kilometers to the south-west of the port city of Iquique in the north of Chile, the same area of northern Chile
where a massive 8.2 earthquake struck on couple weeks ago. The earlier quake,
which caused a tsunami, killed six people and forced almost one million
others to evacuate.
Two powerful 7.6 and 6.4 magnitude aftershocks were also recorded following that quake.
Today's 6.0 quake nested at a depth of 17.5 kilometers (11 miles). There have been no official reports of damage or injury in Chile or Peru, according to Reuters.
USGS earthquake intensity map.
There is no threat of tsunami after the earthquake.
Hundreds of earthquakes have occurred along Chile's far-northern
coast in the past two weeks, starting with a 6.7 magnitude quake that hit on March
16, causing the brief evacuation of 100,000 people in low-lying
areas. No tsunami followed.
An 8.8 magnitude quake and accompanying tsunami hit central Chile
in 2010, killing over 500 people and destroying 220,000 homes,
among other damage.
Seismotectonics of South America (Nazca Plate Region).
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
April 04, 2014 - CHILE - A 6.1 magnitude earthquake has struck Chile, says the US Geological Survey.
USGS earthquake location map.
The epicenter of tremor was located 76 kilometers to the south-west of the port city of Iquique in the north of Chile, the same area of northern Chile
where a massive 8.2 earthquake struck on Tuesday. The earlier quake,
which caused a tsunami, killed six people and forced almost one million
others to evacuate.
Two powerful 7.6 and 6.4 magnitude aftershocks were also recorded on Wednesday.
USGS earthquake shakemap intensity map.
The 6.1 quake nested at a depth of 20 kilometers. There have been no official reports of damage or injury in Chile or Peru, according to Reuters.
There is no threat of tsunami after the earthquake.
Hundreds of earthquakes have occurred along Chile's far-northern
coast in the past two weeks, starting with a 6.7 magnitude quake that hit on March
16, causing the brief evacuation of 100,000 people in low-lying
areas. No tsunami followed.
An 8.8 magnitude quake and accompanying tsunami hit central Chile
in 2010, killing over 500 people and destroying 220,000 homes,
among other damage.
Seismotectonics of South America (Nazca Plate Region).
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
April 03, 2014 - CHILE - A 7.6-magnitude aftershock has rocked the same area of northern Chile
where a massive 8.2 earthquake struck on Tuesday. The earlier quake,
which caused a tsunami, killed six people and forced almost one million
others to evacuate.
USGS earthquake location map.
The Wednesday quake occurred just before 23:43 local time off the northern coast of Chile, 19 km (14 miles) south of Iquique, according to the US Geological Survey (USGS). The epicenter of the latest quake was located at a shallow depth of 40 km (24.9 miles).
Chile’s emergency ministry has ordered a preventative evacuation along the northern Chilean coastline.
However there have been no official reports of damage or injury in Chile or Peru, according to Reuters.
USGS earthquake shakemap intensity map.
USGS earthquake uncertainty ratio map.
A tsunami warning is now in effect for Chile and Peru following the 7.8 quake, according to the Pacific Tsunami Warning Center. “An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicenter within minutes to hours,” the PTWC reported.
“Based on all available data a destructive Pacific-wide tsunami is not expected,” it added.
Chilean President Michelle Bachelet has been evacuated from the Arica coast, local media has reported.
A cameraman records near cars caught under rubble after an earthquake
and tsunami hit the
northern port of Iquique April 2, 2014. (Reuters /
Ivan Alvarado)
Aftershocks measuring magnitudes of 5.6 and 5.8 occurred after the 7.6 quake, according to the USGS. Both were located around 70 to 75 km (43 to 46 miles) southwest of Inquique.
Another strong aftershock, measured at magnitude 6.4, also struck 47 km (29 miles) west of Iquique at around 21:00 local time Wednesday evening.
This comes one day after an 8.2 magnitude quake hit 95 km (59 miles) northwest of the same area, around Iquique.
After Tuesday’s quake, tsunami warnings spurred the evacuation of 900,000 people and 11 hospitals along the coastline, government officials said.
At least six people died following the quake, Chile's Interior Minister Rodrigo Penailillo said. Many of the victims died from heart attacks or falling debris. - RT.
This is rolling coverage. Updates will follow as soon as more information is available. Stay tuned.
Tectonic Summary.
The April 3, 2014 M 7.6 earthquake off the west coast of northern
Chile occurred as a result of thrust motion at a depth of approximately
40 km, 23 km south of the city Iquique. The location and mechanism of
the earthquake are consistent with slip on the plate boundary interface,
or megathrust, between the Nazca and South America plates. At the
latitude of the event, the Nazca plate is subducting beneath South
America at a rate of ~73 mm/yr.
This earthquake is an aftershock of the M 8.2 subduction zone
earthquake that occurred April 1, 2014. The M 8.2 event triggered a
tsunami with measured heights near 2 meters along the northern Chile and
southern Peru coasts. Since the M8.2 event, 47 aftershocks ranging from
M 4.2 to this M 7.8 event have occurred, including a M 6.4 on April 2.
The current seismic sequence was preceeded by a foreshock sequence that
began on March 16, 2014, with a M 6.7 earthquake close to the epicenter
of the April 1 M 8.2 event. This segment of the subduction zone, known
as the Iquique or Northern Chile seismic gap, last ruptured during the
1877 M8.8 Iquique earthquake. Other recent large plate boundary ruptures
bound the possible rupture area of the April 1 event, including the
2001 M 8.4 Peru earthquake adjacent to the south coast of Peru to the
north, and the 2007 M 7.7 Tocopilla, Chile and 1995 M 8.1 Antofagasta,
Chile earthquakes to the south.
Seismotectonics of South America (Nazca Plate Region).
The
South American arc extends over 7,000 km, from the Chilean margin
triple junction offshore of southern Chile to its intersection with the
Panama fracture zone, offshore of the southern coast of Panama in
Central America. It marks the plate boundary between the subducting
Nazca plate and the South America plate, where the oceanic crust and
lithosphere of the Nazca plate begin their descent into the mantle
beneath South America. The convergence associated with this subduction
process is responsible for the uplift of the Andes Mountains, and for
the active volcanic chain present along much of this deformation front.
Relative to a fixed South America plate, the Nazca plate moves slightly
north of eastwards at a rate varying from approximately 80 mm/yr in the
south to approximately 65 mm/yr in the north. Although the rate of
subduction varies little along the entire arc, there are complex changes
in the geologic processes along the subduction zone that dramatically
influence volcanic activity, crustal deformation, earthquake generation
and occurrence all along the western edge of South America.
Most
of the large earthquakes in South America are constrained to shallow
depths of 0 to 70 km resulting from both crustal and interplate
deformation. Crustal earthquakes result from deformation and mountain
building in the overriding South America plate and generate earthquakes
as deep as approximately 50 km. Interplate earthquakes occur due to slip
along the dipping interface between the Nazca and the South American
plates. Interplate earthquakes in this region are frequent and often
large, and occur between the depths of approximately 10 and 60 km. Since
1900, numerous magnitude 8 or larger earthquakes have occurred on this
subduction zone interface that were followed by devastating tsunamis,
including the 1960 M9.5 earthquake in southern Chile, the largest
instrumentally recorded earthquake in the world. Other notable shallow
tsunami-generating earthquakes include the 1906 M8.5 earthquake near
Esmeraldas, Ecuador, the 1922 M8.5 earthquake near Coquimbo, Chile, the
2001 M8.4 Arequipa, Peru earthquake, the 2007 M8.0 earthquake near
Pisco, Peru, and the 2010 M8.8 Maule, Chile earthquake located just
north of the 1960 event.
USGS plate tectonics for the region.
Large
intermediate-depth earthquakes (those occurring between depths of
approximately 70 and 300 km) are relatively limited in size and spatial
extent in South America, and occur within the Nazca plate as a result of
internal deformation within the subducting plate. These earthquakes
generally cluster beneath northern Chile and southwestern Bolivia, and
to a lesser extent beneath northern Peru and southern Ecuador, with
depths between 110 and 130 km. Most of these earthquakes occur adjacent
to the bend in the coastline between Peru and Chile. The most recent
large intermediate-depth earthquake in this region was the 2005 M7.8
Tarapaca, Chile earthquake.
Earthquakes can also be
generated to depths greater than 600 km as a result of continued
internal deformation of the subducting Nazca plate. Deep-focus
earthquakes in South America are not observed from a depth range of
approximately 300 to 500 km. Instead, deep earthquakes in this region
occur at depths of 500 to 650 km and are concentrated into two zones:
one that runs beneath the Peru-Brazil border and another that extends
from central Bolivia to central Argentina. These earthquakes generally
do not exhibit large magnitudes. An exception to this was the 1994
Bolivian earthquake in northwestern Bolivia. This M8.2 earthquake
occurred at a depth of 631 km, making it the largest deep-focus
earthquake instrumentally recorded, and was felt widely throughout South
and North America.
Subduction of the Nazca plate is
geometrically complex and impacts 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 subduction beneath the South America plate. Three
segments are characterized by steeply dipping subduction; the other two
by near-horizontal subduction. The Nazca plate beneath northern Ecuador,
southern Peru to northern Chile, and southern Chile descend into the
mantle at angles of 25° to 30°. In contrast, the slab beneath southern
Ecuador to central Peru, and under central Chile, is subducting at a
shallow angle of approximately 10° or less. In these regions of
“flat-slab” subduction, the Nazca plate 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. - USGS.
Chile's Magnitude 8.2 Earthquake May Be A Forewarning Of A Larger Event.
Chile is beginning to dig out from a massive 8.2 magnitude earthquake
that struck the region at 8:46 p.m. local time Tuesday evening about 52
miles northwest of the mining town of Iquique, according to the USGS. At
least six people are confirmed dead and tens of thousands have been
evacuated from their homes.
The earthquake touched off tsunami warnings and, according to the BBC,
waves up to six feet battered the shoreline in some areas. Widespread
power outages, fires and landslides were also complicating rescue
efforts. As well, numerous aftershocks were felt throughout the night,
including a 6.2 tremor.
Several regions have been declared disaster areas by the government in hopes of "avoiding instances of looting and disorder."
Shortly after the quake, President Michelle Bachelet promised troops and
police reinforcement would be sent to maintain public order during
rebuilding and repair.
"We're leaving with the children and what we can, but everything is
clogged up by people fleeing buildings by the beach," said 32-year old
Liliana Arriaza, who was driving away with her three children, according
to a Reuters report.
Bachelet said the country had "faced the emergency well" and called on
those in the affected regions "to keep calm and follow instructions from
the authorities."
The country's interior minister told Chilean TV that
the quake allowed 300 woman inmates to escape from a prison in Iquique.
Officials later said that 26 had been recaptured.
WATCH: Chile 8.2 magnitude earthquake blackout terror - Screams, panic as power dies.
At press time, the government said that 50 percent of the power has been restored to affected regions.
While this was already considered a massive earthquake, geologists say
that an even bigger temblor may be lurking in the region's future.
"This magnitude 8.2 is not the large earthquake that we were expecting
in this area," Mark Simons, a geophysicist at Caltech in Pasadena,
California, told CNN. "We're expecting a potentially even larger earthquake."
"We do not know when it's going to occur," he maintained.
To give a better idea why geologists believe a larger quake is in Chile's forecast, a little science is needed.
Chile sits on an arc of volcanoes and fault lines that circles the
Pacific Ocean. This circle, known as the "Pacific Ring of Fire," sees
frequent earthquakes and volcanic eruptions. And Chile is no stranger to
frequent tremors.
Since 1973, more than a dozen magnitude-7.0 or larger quakes have struck Chile. In more recent years, an M8.8 temblor
killed 500 people when it rocked the region in 2010. The quake was so
violent, it moved the whole city about 10 feet to the west.
Simons said Tuesday's quake was of much interest because the fault line
along Chile's coast has been in constant shift for the past 140 years.
NOAA's Pacific Tsunami Warning Center's near real-time animation for the
tsunami from northern Chile on 1 April 2014 resulting from an offshore
8.2 magnitude earthquake in the region. The animation shows simulated
tsunami wave propagation for 30 hours followed by an "energy map"
showing the maximum open-ocean wave heights over that period.
WATCH: Tsunami Animation - 8.2 Magnitude Earthquake In Chile On April 1-2, 2014 .
In recent weeks, as many as 100 smaller quakes have been recorded. But
late last month the region was affected by two larger tremors - a 6.7-
and a 6.1-m.
Simons explains that when a quake occurs the surface can rupture and the
two sides of the fault slip past each other. However, he said that no
surface rupture occurred in the latest quake. And, he added, it "hasn't
ruptured in 140-odd years."
He said it is only a matter of time, however, until an earthquake causes surface rupture.
"We expect another 8.8-8.9 earthquake here sometime in the future,"
Simons told CNN. "[But,] it may not occur for many, many years."
As for last night's temblor, the Pacific Tsunami Warning Center issued
an initial warning for Chile, Peru, Ecuador, Colombia and Panama.
However, all warnings were later lifted except for Chile and Peru.
Tsunami watches were also issued for Costa Rica, Nicaragua, El Salvador,
Guatemala, Mexico and Honduras. As well, a tsunami advisory was issued
for Hawaii, although no disaster was expected to hit the island state.
WATCH: Tsunami observed in Japan.
"Sea level changes and strong currents may occur along all coasts that
could be a hazard to swimmers and boaters as well as to persons near the
shore at beaches and in harbors and marinas," the PTWC said in a
statement.
Japan's Meteorological Agency said that a tsunami of up to three feet
might hit Japan's Pacific Coast about 5:00 a.m. Thursday. After
collecting more data it said it may issue a tsunami advisory early
Thursday.
Patrick Moore, a British expatriate living in Antofagasta, Chile told
the BBC that there had been several tremors since the last quarter of
2013.
"But this earthquake, even with the increased distance, seemed to last a
lot longer," Moore said. "I knew it was bad so I immediately went
online to see what had happened and saw a tsunami warning that's been
put in place which confirmed my fears that it was a big one."
The largest earthquake to hit Chile in recent memory was the 1960
9.5-magnitude event that caused about 1,655 deaths as well as a tsunami
that hit Hawaii and Japan. By comparison, the 2011 Japan earthquake that
killed 15,000 people and caused a nuclear disaster was a 9.0-magnitude
temblor.
- Red Orbit.
