Sumatra experiences frequent seismic activity because it is located near the boundary of two of Earth's tectonic plates. Earthquakes occur at 'subduction zones,' such as the one west of Indonesia, when one tectonic plate is forced under another--or subducts. Instead of sliding across one another smoothly, the plates stick, and energy builds up until they finally slip or 'rupture', releasing that stored energy as an earthquake.
These earthquakes can generate tsunamis when the seafloor moves up or down rapidly. But why do some earthquakes, such as the 2004 Sumatra "Boxing Day Tsunami", create large hazards, while others do not?
Three months after the catastrophic December 2004 earthquake and tsunami events, another strong, albeit smaller, quake occurred immediately to the south, but this earthquake triggered only a local tsunami.
"Many people wondered why the 2004 quake was so large," said Sean Gulick, a geophysicist from the University of Texas at Austin. "Perhaps a more interesting question is: why wasn't it larger? Why did the rupture occur as two events instead of one large one?"
With support from the National Science Foundation (NSF), Gulick joined an international research team to try to figure out why there were two quakes, and what made them so different. Working aboard the research vessel Sonne, the scientists used seismic instruments to study layers of sediment beneath the seafloor with sound waves.
The researchers found that the fault surface where the two tectonic plates meet, called a décollement, has different properties in the two earthquake rupture regions. In the southern part of the 2004 area, the décollement imaging results show a bright reflection, while the décollement in the 2005 area does not. This difference in the images suggests changes in the composition of the rocks--or the fault itself--between the rupture areas. These characteristics may partially explain why the areas did not rupture together and may also contribute to differences in the tsunamis produced by both events.
Scientists believe this difference in composition, combined with several other factors, resulted in the fault slipping over a much wider part of the margin and farther seaward in the 2004 event.They suspect that because more earth moved, more of the seafloor moved and more water was displaced, resulting in a larger tsunami.
Compared to similar studies of other subduction zones around the world, the team believes the region of the 2004 Sumatra earthquake is very unusual, and that tsunami hazards may be particularly high in this area.
The results of their study appear in the July 9 edition of the journal Science. The paper's lead author is Simon Dean, of the University of Southampton (UK). Researchers from the University of Texas at Austin (US), the Agency for the Assessment and Application of Technology (Indonesia), and the Indonesia Institute for Sciences also contributed to the work.
Lisa Van Pay | EurekAlert!
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
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,...
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...
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...
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...
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...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
21.08.2017 | Materials Sciences
21.08.2017 | Health and Medicine
21.08.2017 | Materials Sciences