Are Mega Earthquakes on the Rise? | Japan Earthquake & Tsunami | Natural Disasters | Indonesian Tsunami | LiveScience
These images show the effects of the tsunami on Japan's coastline. The image on the left was taken on Sept. 5, 2010; the image on the right was taken on March 12, 2011, one day after an earthquake and resulting tsunami struck the island nation.
CREDIT: German Aerospace Center (DLR)/Rapid Eye
(ISNS) — The devastating 2004 Indonesian tsunami, with its death toll of as many as 250,000 people, was caused by the first magnitude-9.0 earthquake since 1967. A succession of smaller but still destructive tremors in Haiti, Chile, and New Zealand — surpassed by this year's magnitude-9.0 quake in Japan — has some researchers wondering whether the number of large earthquakes is on the rise.
An earthquake represents the abrupt release of seismic strain that has built up over the years as plates of the Earth's crust slowly grind and catch against each other. Giant earthquakes live up to their fearsome name. The biggest ever recorded was the magnitude-9.5 Chile earthquake of 1960. It accounts for about a quarter of the total seismic strain released worldwide since 1900. In just three minutes, the recent quake in Japan unleashed one-twentieth of that global total according to geophysicist Richard Aster at the New Mexico Institute of Mining and Technology in Socorro. [...]
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This article is provided by Inside Science News Service, which is supported by the American Institute of Physics.
I don't know how hard it is to understand. The earthquake, that release of pressure, results in sound waves that travel through different mediums differently. Those that don't travel through liquid (S-waves, I think) would be reflected and deflected through the crust until they hit a surface not against magma or water out of which they could disperse or until all their energy had been absorbed. Along the way they'd be breaking up, passing between plates, becoming aftershocks (when they end up back at the source and shake things down a bit more), tremors in random different places, sometimes triggering new events at other stress points, and it would cycle, but randomly, as old energies were dissipated and new ones were created in a beautiful harmonic symphony. Nature is ordered, but rarely neat.
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