Scientists complete first drill into earthquake-generating region near JapanApril 22nd, 2008 - 2:04 pm ICT by admin
London, April 22 (ANI): Scientists have completed the first stage of a plan to drill down into an earthquake-generating region near Japan, with the project seeing holes bored 1.4km into the sea floor, producing 3D images of stresses inside the quake zone.
According to a report by BBC News, the earthquake-generating region is known as the Nankai Trough, which produced major lethal earthquakes and tsunamis during the last century.
According to Harold Tobin, the projects co-chief scientist, the Sumatra quake is a good example of the fact that the greatest quakes on the planet happen in subduction zones, where one tectonic plate is sliding beneath another.
And virtually all of the big quakes, the ones of magnitude eight or nine or above, happen at sea; so we have to go to sea to study the plate boundaries, the actual faults, that generate those earthquakes, he said.
The five months from last September saw eight holes drilled to various depths in the Nankai Trough, using the new Japanese research vessel Chikyu.
The drill bits travelled through the megasplay zone, the region above the actual subduction path, which is riddled with faults.
Three-dimensional scans performed aboard Chikyu on cores taken from these boreholes reveal some of the stresses that the rock is placed under as the Philippines tectonic plate descends underneath Japan.
We use this medical CT (computed tomography) scanner that scans through core samples instead of the human body, said co-chief scientist Masataka Kinoshita from the Japan Agency for Marine-Earth Science and Technology.
This gives 3D density images, just like in the human body we would see brain or bones or other things, he added.
Most of the stress lines, as researchers anticipated, lie along the direction that the plates are traveling.
Mapping these stress lines could indicate which portions along the subduction zone are locked - where the descending plate snags and sticks to the one above - and which are loose and able to move freely.
That in turn would set some parameters for the likely scale of a tsunami, which is believed to occur in this region when the forces on the snagged upper plate grow too large and the plate snaps upward violently, releasing its accumulated energy into the water above.
According to Tobin, Later this year, we will do some more shallow drilling. Then in 2010 or 2012, we aim to drill two deep holes down to about 6 km.
We can then get cores through the fault zone where it branches down there; and we will also place instruments down inside the boreholes, he added. (ANI)
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Tags: 3d images, boreholes, chief scientist, core samples, dimensional scans, earth science, harold tobin, japanese research, kinoshita, medical ct, nankai trough, plate boundaries, quake zone, research vessel, sea floor, stress lines, subduction zone, subduction zones, sumatra quake, tectonic plate