|USGS earthquake location map.|
The U.S. Geological Survey said the quake was very shallow, only 6.2 miles below the seabed, and struck at 6:46 p.m. 62 miles northwest of the mining port of Iquique, near the Peruvian border.
“An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines near the epicenter within minutes and more distant coastlines within hours,” the tsunami center said.
Iquique is a key copper exporting port, close to the country’s main copper mines. Mining companies Codelco and BHP Billiton said that had not yet received reports of damage to mines.
|USGS earthquake shakemap intensity map.|
The warning said that aside from Chile, the coasts of Peru, Ecuador, Colombia, Panama, Costa Rica and Nicaragua were also at risk. A tsunami of up to 6.3 feet could strike the town of Pisagua, Chile, within 44 minutes of the quake, it said.
The Chile National Office of Emergency of the Interior Ministry has ordered a preventative evacuation for the coastal areas of Arica, Parinacota, and Tarapacá, La Tercera reported.
|USGS earthquake uncertainty ratio map.|
The Weather Channel reports a 2m tsunami has been observed coming ashore at Pisaqua, Chile. A 1.7m tsunami was recorded at Iquique.
The Chilean navy said the first tsunami wave had hit the coast within 45 minutes of the quake. No details have yet emerged as to any damage.
The latest quake also shook buildings in parts of the nearby nations of Bolivia and Peru. Waves measuring almost two metres are already striking cities on the northern coast.
Chile’s emergency ministry ONEMI says there have been reports of landslides causing some blockage on roads and highways.
A tsunami is expected to reach nearby cities throughout the night, and local TV images show residents evacuating calmly.
Chile’s Emergency Office says a large tsunami wave is expected to hit the island of Juan Fernandez just before midnight local time.
Three aftershocks – ranging from magnitude 5 to 5.4 – have been reported in northern Chile, according to Telemundo.
|A tsunami energy map released by the National Tsunami Warning Centre after the quake.|
Mega-quakes in this zone are usually followed by devastating tsunamis, including the magnitude 9.5 in 1960 that struck southern Chile, the largest instrumentally recorded earthquake in the world. Other notable shallow tsunami-generating earthquakes include the 1906 magnitude 8.5 earthquake near Esmeraldas.
Additionally most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 kilometres, 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.
|People evacuate buildings in the Chilean port city of Antofagasta|
In 2010, an 8.8-magnitude quake triggered a tsunami that caused major damage in several coastal towns in central-south Chile and killed hundreds of people.
Hundreds of earthquakes have shaken Chile’s far-northern coast in the past two weeks, keeping people on edge as scientists said there was no way to tell if the unusual string of tremors was a harbinger of an impending disaster.
|Map of all seismic activity from the past 2 weeks. iris.edu/seismon/|
The unnerving activity began with a strong magnitude-6.7 quake on March 16 that caused more than 100,000 people to briefly evacuate low-lying areas, although no tsunami materialised and there was little physical damage from the shaking.
This is rolling coverage. Updates will follow as soon as more information is available. Stay tuned.
The April 1, 2014 M8.2 earthquake in northern Chile occurred as the result of thrust faulting at shallow depths near the Chilean coast. The location and mechanism of the earthquake are consistent with slip on the primary plate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of the earthquake, the Nazca plate subducts eastward beneath the South America plate at a rate of 65 mm/yr. Subduction along the Peru-Chile Trench to the west of Chile has led to uplift of the Andes mountain range and has produced some of the largest earthquakes in the world, including the 2010 M 8.8 Maule earthquake in central Chile, and the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile.
The April 1 earthquake occurred in a region of historic seismic quiescence – termed the northern Chile or Iquique seismic gap. Geodetic modeling indicates that the subducting and overriding plates are partially to fully-locked, implying that large earthquake are possible along the plate boundary megathrust. Historical records indicate a M 8.8 earthquake occurred within the Iquique gap in 1877, which was preceded immediately to the north by an M 8.8 earthquake in 1868.
A recent increase in seismicity rates has occurred in the vicinity of the April 1 earthquake. An M6.7 earthquake with similar faulting mechanism occurred on March 16, 2014 and was followed by 60+ earthquake of M4+, and 26 earthquakes of M5+. The March 16 earthquake was also followed by three M6.2 events on March 17, March 22, and March 23. The spatial distribution of seismicity following the March 16 event migrated spatially to the north through time, starting near 20oS and moving to ~19.5oS. The initial location of the April 1 earthquake places the event near the northern end of this seismic sequence. 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. Other nearby events along the plate boundary interface include an M 7.4 in 1967 as well as an M 7.7 in 2005 in the deeper portion of the subduction zone beneath onland Chile.
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.