Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study of 2004 tsunami forces rethinking of giant earthquake theory

07.03.2006


The Sumatra-Andaman earthquake of Dec. 26, 2004, was one of the worst natural disasters in history, largely because of the devastating tsunami that followed. Now, scientists have discovered that regions of the earth previously thought to be immune to such events may actually be at high risk of experiencing them.



Their findings, reported in this week’s issue of the journal Nature, suggest researchers may need to revise their former ideas about where giant earthquakes are likely to occur.

"This earthquake didn’t just break all the records, it also broke some of the rules," says scientist Kerry Sieh of Caltech, an author of the report.


"These exciting findings can help us learn how earthquakes such as this are generated, and therefore which areas around the world are at risk from these natural disasters," says Eva Zanzerkia, program director in the National Science Foundation’s (NSF) division of earth sciences, which funded the research. "This discovery has global implications for understanding earthquake hazards."

Like all giant earthquakes, the 2004 event occurred along a giant earthquake fault where the Indian and Australian tectonic plates are diving beneath the margin of southeast Asia. Although the portion of the fault that ruptured lies several miles deep in the Earth’s crust, the event caused considerable movement at the surface itself because it suddenly released so much long-accumulating elastic strain.

Sieh and his coworkers measured these surface motions by three different techniques. In one, they measured the shift in position of GPS stations whose locations had been accurately determined prior to the earthquake.

In the second method, they studied corals on island reefs: the top surfaces of these corals are normally at the water surface, so the presence of corals with tops above or below the water level indicated that the Earth’s crust rose or fell by that amount during the earthquake.

Finally, the researchers compared satellite images of island lagoons and reefs taken before and after the earthquake: changes in the color of the seawater or reefs indicated a change in the water’s depth and hence a rise or fall of the crust at that location.

On the basis of these measurements the researchers found that the surface rupture spanned a distance of up to 93 miles, and that along this huge contact area, the surfaces of the two plates slid against each other by up to 60 feet. Extrapolating to the deeper fault, they also found that the 2004 earthquake was caused by rupture of a 1,000-mile stretch of the megathrust--by far the longest of any recorded earthquake.

Indeed, the researchers say, the 2004 disaster was so much larger than any previously known rupture of this type that scientists may need to reassess many subduction zones that were previously thought to be at low risk.

For example, "the Ryukyu Islands between Taiwan and Japan are in an area where a large rupture would probably cause a tsunami that would kill a lot of people along the Chinese coast," says Sieh. "And in the Caribbean, it could well be an error to assume that the entire subduction zone from Trinidad to Barbados and Puerto Rico is not seismic."

The message of the 2004 earthquake to the world, says Sieh, "is that you shouldn’t assume that a subduction zone, even though it’s quiet, is incapable of generating great earthquakes."

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

More articles from Earth Sciences:

nachricht In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

nachricht Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>