We have scars... May 1, 2005 19:35:03 GMT -6
Post by Chicago Astronomer Joe on May 1, 2005 19:35:03 GMT -6
Earth’s gravity scar
A new ESA study predicts that the devastating Sumatran earthquake, which resulted in the tragic tsunami of 26 December 2004, will have left a ‘scar’ on Earth’s gravity that could be detected by a sensitive new satellite, due for launch next year.
The Sumatran earthquake measured 9 on the Richter scale and caused widespread devastation and death when it struck unexpectedly late last year. Thankfully, earthquakes of this magnitude are rare events, taking place perhaps once every two decades.
Seismological data suggests that, during the event, the seafloor on either side of a fault line running for 1000 km along the bottom of the Indian Ocean dramatically changed height, producing a ledge, 6 metres high. Such a large-scale movement will change the gravitational field of the Earth. Roberto Sabadini and Giorgio Dalla Via, University of Milan, and colleagues have calculated this change. They found that the Earth’s gravity altered, in an instant, by as much as is expected from six years' worth of melting at the Patagonian Ice Fields in southernmost South America.
It may seem surprising that Earth’s gravity is not equally strong at all points of the globe. Instead, it varies by a small fraction due to the presence of such things as mountains or deep ocean trenches. The tides and ocean circulation patterns also affect the gravity, as does the rotation of the Earth itself, which bulges out the planet’s equator and makes its diameter 21 kilometres wider than the pole-to-pole distance.
More here from the ESA: www.esa.int/esaCP/SEMCO8NQS7E_index_0.html
It will be interesting to see the gravity shape of the Earth when the new sat is in orbit.