Tsunami is Helping Scientists to Study Earth

Indo-Asian News Service ^ | June 10, 2005

[nickcarraway]

Oscillations started by the Sumatra-Andaman tsunami quakes last December are providing vital information about the composition of the Earth as well as the size and duration of the tremors, scientists have said.

A team of international scientists led by Jeffrey J Park of the US has said that the Sumatra-Andaman earthquake produced the best documentation of Earth's free oscillations ever recorded, according to a press release posted in science portal EurekAlert.

"This earthquake may resolve several controversies, such as whether a heavy slagheap of old tectonic plates is stuck near the core-mantle boundary beneath Africa, or even whether microscopic crystals of pure iron in Earth's inner core are aligned with the rotation axis," said Park.

Seismic waves from the 9-magnitude Sumatra earthquake reached a monitoring station in Sri Lanka within four minutes and caused the ground to rise and fall 3.6 inches. It registered on seismometers worldwide within 21 minutes.

The data of Park and his colleagues supports a model of the Sumatra-Andaman earthquake that lasted about 10 minutes. The rupture moved massive slabs of rock at least 65 ft (20 m) over the longest distance ever recorded, more than 800 miles (1,280 km).

The first report of free oscillations was from hand-digitised analogue recordings of the 9+ magnitude Chilean earthquake on 22 May 1960. The seismic records from the 1960s events were fragmentary, because the technology of the time could not record all earthquake motions.

However, the December earthquake tested the current global digital broadband technology. More than 400 stations around the world provided data, including a site at the South Pole with a seismometer buried deep in the ice sheet.

[sourcery]

That earthquate caused all sorts of waves.