Saturday, February 27, 2010

Central Chile:Earthquake-February 27, 2010 Causes and Effects

An earthquake of magnitude 8.8 struck off coastal Chile on Saturday, February 27, 2010 at 06:34:14 UTC. The location was 35.846°S, 72.719°W.The USGS reported the epicentre of the quake was 100 km (60 miles) NNW of Chillan, 105 km (65 miles) WSW of Talca, 115 km (70 miles) NNE of Concepcion, and 325 km (200 miles) SW of SANTIAGO.
The focus was approximately 21 miles below the surface of the Pacific Ocean. The death toll from Chile's earthquake has more than doubled to 708 and is expected to rise further, President Michelle Bachelet has said. The quake sent a wave across the sea towards Hawaii, Australia, New Zealand and the US, sparking tsunami alerts. The 8.8-magnitude earthquake released 500 times the energy of the 7.0-magnitude quake that struck Haiti last month.Shock waves were powerful enough to be felt 1,000 miles away in Argentina. At least 85 people died in the region of Maule alone. Many deaths were also in reported in the regions of Santiago, O'Higgins, Biobio, Araucania and Valparaiso. A major bridge at Concepcion collapsed into the Biobio river
Some of the worst damage was in the second largest city of Conception.
According to the Mirror Newspaper

Homes and bridges were destroyed, buildings engulfed in flames as gas pipes burst and trucks plunged into vast cracks which had appeared in the road. The capital city of Santiago, 200 miles from the epicentre, shook for about a minute-and-a-half, bringing buildings crashing to the ground. Minutes after the quake, terrified residents streamed on to the streets crying and hugging each other for comfort. Many were too scared to return to their homes. Throughout the morning aftershocks of up to 6.9 on the Richter Scale shook the city.
Tectonic Summary
This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 80 mm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate.
Coastal Chile has a history of very large earthquakes. Since 1973, there have been 13 events of magnitude 7.0 or greater. The February 27 (2010) shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 – the largest earthquake worldwide in the last 200 years or more. This giant earthquake spawned a tsunami that engulfed the Pacific Ocean. An estimated 1600 lives were lost to the 1960 earthquake and tsunami in Chile, and the 1960 tsunami took another 200 lives among Japan, Hawaii, and the Philippines. Approximately 870 km to the north of the February 27 earthquake is the source region of the magnitude 8.5 earthquake of November, 1922. This great quake significantly impacted central Chile, killing several hundred people and causing severe property damage. The 1922 quake generated a 9-meter local tsunami that inundated the Chile coast near the town of Coquimbo; the tsunami also crossed the Pacific, washing away boats in Hilo harbor, Hawaii. The magnitude 8.8 earthquake of February 27, 2010 ruptured the portion of the South American subduction zone separating these two massive historical earthquakes (USGS)

It is highly likely that a massive eartquake of magnitude 9.5 -similar to 1960- will strike coastal Chile at some time in the future as pressure builds up along the subduction zone where the Nazca Plate subducts the South American Plate. This latest quake is certainly not the last.

1 comment:

WgS said...

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