Acehtsunami

The data, collected using a commercial ship, reveals the structure of Earth’s crust below the Nankai Trough, which is known to generate destructive tsunamis.The Nankai Trough is in a subduction zone, 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 several world’s largest earthquakes.Using the 3D seismic images, researchers restructured how layers of rock and sediment have cracked and shifted over time.

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This research helped them to find two things that contribute to large tsunamis.First, they validated 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, bearing a column of water with it and setting up a series of tsunami waves that extend outward.

Secondly, the team discovered that the recent fault activity, maybe 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 dislocation of the seafloor and a larger vertical component of seafloor displacement that is more effective in generating tsunamis,” said Nathan Bangs, superior research scientist at the Institute for Geophysics at The University of Texas.