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

More articles from Earth Sciences:

nachricht NASA sees the end of ex-Tropical Cyclone 02W
21.04.2017 | NASA/Goddard Space Flight Center

nachricht New research unlocks forests' potential in climate change mitigation
21.04.2017 | Clemson University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>