Saturday, February 27, 2010

Earthquake: South America

By now you might have heard there was an overnight earthquake in Chile, South America. The earthquake measured at 8.8 magnitude.

To put the Chile earthquake in perspective lets compare it to the devastating earthquake that hit Haiti in January. The Haiti earthquake was a 7.0 magnitude earthquake. This means that the Chile earthquake was roughly 850 to 900 times stronger than the Haiti earthquake.

I have been looking over some of the data from the US Geological Survey's earthquake website. The earthquake started at 3:34am Chile time. The epicenter was 200 miles southwest of Santiago, Chile.

This was a deep earthquake. It was measured at 21.7 miles below the surface. That is important to know. The deeper the earthquake often times the less shaking takes place at the surface. Earthquakes in southeast Missouri are typically much more shallow. Generally in the 2-7 miles deep.

Just like Haiti, strong aftershocks continue to shake Chile. Through 7:40am CT there have been 19 aftershocks ranging from 5.0 magnitude to 6.2 magnitude.

Another threat from the earthquake is the possibility of tsunamis. At one point this morning there were Tsunami Warnings in place for 40 countries across the world. Hawaii will be evacuating some locations across the islands at 6am Hawaii time. You can follow coverage from Hawaii from our Raycom News Network affiliate KHNL on their website. You can also watch their LIVE coverage here. The waves are expected to hit Hawaii around 3:00pm CT Saturday afternoon.

Additional information from the USGS site regarding the region the earthquake hit.

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 shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 – the largest instrumentally recorded earthquake in the world. This magnitude 9.5 earthquake killed 1655 people in southern Chile and unleashed a tsunami that crossed the Pacific, killing 61 people in Hawaii, Japan, 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.

A large vigorous aftershock sequence can be expected from this earthquake.


What was the New Madrid Earthquake of 1800's?

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