MONUMENTAL EARTH CHANGES: Global Seismic Uptick – 7.6 And 6.4 Aftershocks Hit Same Area Of Northern Chile As Tuesday’s 8.2 Magnitude Earthquake That Killed 6 People! [PHOTOS+VIDEOS+MAPS+ESTIMATES]

April 02, 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.

7.6 and 6.4 aftershocks hit same area of northern Chile as Tuesday's 8.2 quake resulting in tsunami.
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.

7.6 and 6.4 aftershocks hit same area of northern Chile as Tuesday's 8.2 quake resulting in tsunami.
USGS earthquake shakemap intensity map.

7.6 and 6.4 aftershocks hit same area of northern Chile as Tuesday's 8.2 quake resulting in tsunami.
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.

7.6 and 6.4 aftershocks hit same area of northern Chile as Tuesday's 8.2 quake resulting in tsunami.
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.

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.

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