Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sumatra-Andaman earthquake modeled and mapped

20.05.2005


The earthquake that generated the Sumatran-Andaman Islands tsunami caused massive devastation, but exactly what happened beneath the ocean is the focus of modeling activities by an international team of geoscientists.



"The earthquake rupture ran a distance equivalent to the distance from Jacksonville, Florida to Boston, Mass.," says Charles J. Ammon, associate professor of geosciences at Penn State. "This earthquake lasted just under 10 minutes, while most large earthquakes take only a few seconds and movement probably continued past that which we can determine from seismic information."

Ammon and his colleagues looked at what happened during the Sumatra-Andaman Earthquake on Dec. 26, 2004 and the subsequent earthquake on March 28, 2005, using a variety of models.


"We were trying to map out spatially and temporally what was going on," he adds. "The last earthquake in this size range happened more than forty years ago. This is the first time these models could be constructed for such a large earthquakes."

Previous earthquakes in the range of the Sumatra-Andaman great earthquake occurred in Kamchatka, Russia in 1952; the Aleutians in 1957; southern Chile in 1960, and Prince William Sound, Alaska in 1964, long before current computational methods for modeling earthquakes were possible. Also, during the earlier large earthquakes, groups such as the Incorporated Research Institutes for Seismology, a National Science Foundation-supported group, and the Federation of Digital Broadband Seismographic Networks, an international group, did not exist. These two groups provided the global seismological data that made the models possible.

The researchers report in a special section of today’s (May 20) issue of Science that "the 25 December 2004 Sumatra-Andaman and the 28 March 2005 earthquakes produced the most extensive high-quality broadband seismic data ever recorded for great earthquakes."

Great earthquakes usually occur along subduction zones and the Sumatra-Andaman earthquake was no exception. Subduction occurs when one of the Earth’s tectonic plates slides beneath another of the Earth’s plates. In this case the eastern edge of the Indo-Australian plate is sliding beneath the western edge of the southeastern Eurasian plate.

The researchers found that the earthquake originated and was strongest just north and west of the island of Sumatra, Indonesia and decreased in strength as it ruptured north to the Nicobar and Andaman Islands, India in the Bay of Bengal.

"The earthquake in Dec. 2004 stared slowly with relatively little slip in the first minute," says Ammon. "After 40 to 60 seconds, there was a large amount of energy released."

Usually, this subduction fault stays locked between earthquakes, but away from the fault, the plates move at a rate of 1.5 to 2 inches a year. Pressure builds up at the fault over the years until, during an earthquake, they abruptly slip past each other, one going downward and the other moving upward. This creates not only horizontal, but vertical movement during an earthquake. In some places, the Sumatra-Andaman earthquake moved nearly 50 feet in a combination of horizontal and vertical motion.

The researchers used different approaches and different data sets to create their models. Their goal was to map out the rupture history and variation along the fault. Ammon created a 1-dimensional model using seismic surface wave data, an Oxford University team created a 2-dimensional model using seismic body wave data and California Institute of Technology and URS Corporation used different combinations of body and surface waves for their models.

The models showed that the length of the first earthquake was about 960 miles, began just northwest of Sumatra and moved through the Nicobar Islands to the Andaman Islands decreasing in intensity. Fault movement from this earthquake was nearly all north of the epicenter. The largest slip, that of about 50 feet, occurred just off Sumatra. The models also showed that the March 2005 earthquake began south of the first earthquake and was much shorter in both time and space. These are the largest two earthquakes recorded on modern equipment.

The models suggest a speed of one to two miles per second for the speed at which the earthquake expanded northward. The models also suggest that the fault continued to move, albeit much more slowly long after the seismic signals from the earthquake became too slow to record.

"We were lucky to have lots of data to use for our models," says Ammon. "We had a very broad range of frequencies available from which to draw our data."

Besides Ammon, the researchers included Ji Chen, Vala Hjorteifsdottir, Hiroo Kanamori, Don Helmberger Cal Techand Sidao Ni, Cal Tech and University of Science and Technology, China; Hong-Kie Thio and Gene Ichinose, URS Corporation; David Robinson and Shamita Das, Oxford University; Thorne Lay, University of California, Santa Cruz; Jascha Polet, Institute for Crustal Studies, and David Wald, U. S. Geological Survey.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>