New study might determine explanation for Tsunami prone zones

November 16th, 2007 - 4:23 pm ICT by admin  

Washington, Nov 16 (ANI): A new research by geoscientists would help to assess why particular regions of the world are more prone to giant tsunamis than others.
Using 3D seismic data collected from a region of the Pacific seafloor known as the Nankai Trough, researchers would evaluate that why earthquakes below some parts of the seafloor trigger large tsunamis while earthquakes in other regions do not.
The data, collected using a commercial ship, reveals the structure of Earth’s crust below the Nankai Trough, which is known to generate devastating tsunamis.
The Nankai Trough is in a subduction zone, an area where two tectonic plates are colliding and pushing one plate down below the other. The grinding of one plate over the other in subduction zones leads to some of the world’s largest earthquakes.
Using the 3D seismic images, researchers reconstructed how layers of rock and sediment have cracked and shifted over time.
This research helped them to find two things that contribute to big tsunamis.
First, they confirmed the existence of a major fault that runs from a region known to unleash earthquakes about 10 kilometers (6 miles) deep right up to the seafloor. When an earthquake happens, the fault allows it to reach up and move the seafloor up or down, carrying a column of water with it and setting up a series of tsunami waves that spread outward.
Secondly, the team discovered that the recent fault activity, probably including the slip that caused the 1944 event (which killed 1200 people), has shifted to landward branches of the fault, becoming shallower and steeper than it was in the past.
“That leads to more direct displacement of the seafloor and a larger vertical component of seafloor displacement that is more effective in generating tsunamis,” said Nathan Bangs, senior research scientist at the Institute for Geophysics at The University of Texas.
The images produced in this project will be used by scientists in the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), an international effort designed to drill, sample and instrument the earthquake-causing portion of Earth’s crust, where violent, large-scale earthquakes have occurred repeatedly throughout history.
“The 2004 Indonesian tsunami was a big surprise. It’s still not clear why that earthquake created such a large tsunami,” said Bangs. “By understanding places like Nankai, we’ll have more information and a better approach to looking at other places to determine whether they have potential to generate tsunamis,” he added. (ANI)

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