Indonesia quake surprises scientists

2012-04-12 09:54
Los Angeles - The massive earthquake off Indonesia surprised scientists: Usually this type of jolt isn't this powerful.

The biggest earthquakes tend to occur in subduction zones where one plate of the Earth's crust dives under another. This grind produced the 2004 magnitude-9.1 Indian Ocean disaster and the magnitude-9 Japan quake last year.

Wednesday's magnitude-8.6 occurred along a strike-slip fault line similar to California's San Andreas Fault. Scientists say it's rare for strike-slip quakes, in which blocks of rocks slide horizontally past each other, to be this large.

"It's clearly a bit of an odd duck," said seismologist Susan Hough of the US Geological Survey in Pasadena, Calif.

As one of the world's most seismically active places, Indonesia is located on the Pacific "Ring of Fire", an arc of volcanos and fault lines encircling the Pacific Basin. Pressure builds up in the rocks over time and is eventually released in an earthquake.

Wednesday's quake was followed by a magnitude-8.2 aftershock. Both were strike-slip quakes.

"A week ago, we wouldn't have thought we could have a strike-slip earthquake of this size. This is very, very large," said Kevin Furlong, a professor of geosciences at Penn State University.

So large, in fact, that the main shock went into the history books. Record-keeping by the USGS National Earthquake Information Centre ranks Wednesday's shaker as the 11th largest since 1900. It's probably the largest strike-slip event though there's debate about whether a similar-sized Tibet quake in 1950 was the same kind.

A preliminary analysis indicates one side of the fault lurched 70 feet past the other - a major reason for the quake's size. By contrast, during the 1906 magnitude-7.8 San Francisco earthquake along the San Andreas -perhaps the best known strike-slip event - the ground shifted 15 feet.

The Sumatra coast has been rattled by three strong strike-slip quakes since 2004, but Wednesday's was the largest.

Read more on:    indonesia  |  tsunamis

Join the conversation! encourages commentary submitted via MyNews24. Contributions of 200 words or more will be considered for publication.

We reserve editorial discretion to decide what will be published.
Read our comments policy for guidelines on contributions.

linking and moving

2015-04-22 07:36 publishes all comments posted on articles provided that they adhere to our Comments Policy. Should you wish to report a comment for editorial review, please do so by clicking the 'Report Comment' button to the right of each comment.

Comment on this story
Comments have been closed for this article.

Inside News24


Meet instagram star, Pumpkin the racoon

With 300 000 followers and growing Pumpkin is winning over the internet!



The cats that cost R35 000
Miley Cyrus can’t get enough of her new puppy
13 guilty pets
Meet SA's top poacher-catcher

Book flights

Compare, Book, Fly

Traffic Alerts

In order to really connect to your feelings, you need to quieten your mind. Let go of expectations and connect to the moment more

There are new stories on the homepage. Click here to see them.


Create Profile

Creating your profile will enable you to submit photos and stories to get published on News24.

Please provide a username for your profile page:

This username must be unique, cannot be edited and will be used in the URL to your profile page across the entire network.


Location Settings

News24 allows you to edit the display of certain components based on a location. If you wish to personalise the page based on your preferences, please select a location for each component and click "Submit" in order for the changes to take affect.

Facebook Sign-In

Hi News addict,

Join the News24 Community to be involved in breaking the news.

Log in with Facebook to comment and personalise news, weather and listings.