Old fractures caused rare 8.6 magnitude earthquake

Aug 31, 2012

On 11 April 2012, an 8.6 magnitude earthquake occurred 100 kilometers (62 miles) off the coast of Sumatra. This earthquake was unusual in that it originated within the plate rather than at a plate boundary. In fact, it is the largest such earthquake in observed human history. The quake originated under the Wharton Basin in the Indian Ocean, where hundreds of kilometers of rock were under crushing tension, causing the plate to deform at its base. But this deforming zone was also absorbing tension as two plates, the Indian and Australian plates, rotated toward each other.

One month after the earthquake, Satriano et al. revisited the Wharton Basin to reconstruct the rupture history of the events of 11 April to gain a better understanding of the general nature of these rare large within-plate earthquakes. They used a comparatively new tool known as back projection analysis, which tracks radiation that emanates as new locations along a rupture path become active.

Calibrating the back projection analysis with , which scientists use to calculate the travel time and distance of seismic P and S waves that originate at the , the authors find that the events of 11 April had their roots in the old fabric of the Wharton Basin, the floor of which is littered with old fractures. Tension deep within the deformation zone had reactivated one of the north-south aligned fractures. That rupture in turn triggered a series of ruptures of old fractures, generating a slew of strike-slip faulting that traveled westward and ended at the Ninety East Ridge, the north-south oriented seamount chain that bounds the basin, 370 kilometers (230 miles) from the epicenter and 120 seconds later-the timing of the last rupture event.

Explore further: Study shows air temperature influenced African glacial movements

More information: The 2012 Mw 8.6 Sumatra earthquake: Evidence of westward sequential seismic ruptures associated to the reactivation of a N-S ocean fabric, Geophysical Research Letters, doi:10.1029/2012GL052387 , 2012

Related Stories

Sumatra earthquake mysteries examined

May 11, 2012

(Phys.org) -- An earthquake in the Indian Ocean off the coast of Sumatra, Indonesia on 11th April was unusually powerful, at magnitude 8.6, for a “strike-slip” type of quake, and a new analysis of ...

Unusual earthquake gave Japan tsunami extra punch

May 24, 2011

The magnitude 9 earthquake and resulting tsunami that struck Japan on March 11 were like a one-two punch – first violently shaking, then swamping the islands – causing tens of thousands of deaths ...

GPS data reveals more on mega-thrust earthquakes

Apr 29, 2011

(PhysOrg.com) -- New GPS data of the 2010 earthquake that devastated parts of Chile and killed over 500 people is revealing new clues about large earthquakes such as the quake in Chile and the magnitude 9.0 ...

Large Himalaya earthquakes may occur sooner than expected

Dec 07, 2005

While the rupture zones of recent major earthquakes are immune to similar-sized earthquakes for hundreds of years, they could be vulnerable to even bigger destructive temblors sooner than scientists suspect, according to ...

New Sumatra quake takes seismologists by surprise

Oct 01, 2009

The huge earthquake that hit Sumatra occurred at a deep, unexpected location, illustrating the dangerously complex geological mosaic in this area, a seismologist told AFP on Thursday.

Recommended for you

Clean air: Fewer sources for self-cleaning

4 hours ago

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

There's something ancient in the icebox

4 hours ago

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Image: Grand Canyon geology lessons on view

11 hours ago

The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of ...

First radar vision for Copernicus

11 hours ago

Launched on 3 April, ESA's Sentinel-1A satellite has already delivered its first radar images of Earth. They offer a tantalising glimpse of the kind of operational imagery that this new mission will provide ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1 / 5 (3) Aug 31, 2012
Google; "Sunspots and Earthquakes" for quite the interesting article on the matter.
Peter Hent
5 / 5 (1) Sep 01, 2012
Google; "Sunspots and Earthquakes" for quite the interesting article on the matter.


No.
cantdrive85
1 / 5 (1) Sep 01, 2012
Google; "Sunspots and Earthquakes" for quite the interesting article on the matter.


No.


Ignorance is bliss.

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Researchers discover target for treating dengue fever

Two recent papers by a University of Colorado School of Medicine researcher and colleagues may help scientists develop treatments or vaccines for Dengue fever, West Nile virus, Yellow fever, Japanese encephalitis and other ...