Summary Box: Big earthquakes, but no major tsunami
Apr 11, 2012, 3:06 PM
(AP) – EARTHQUAKE STRIKES: An 8.6-magnitude earthquake and an 8.2-aftershock hit off Indonesia’s western coast Wednesday but did not cause a major tsunami.
WHY NOT? These two quakes were strike-slip quakes, which cause a horizontal tearing movement that does not displace the seabed, causing vibrations in the sea instead.
MEGA-THRUST: The tsunami that devastated Japan last year and the 2004 tsunami off Indonesia were mega-thrust earthquakes. They cause the seabed to heave vertically, dispersing large volumes of water.
MAGNITUDE: The magnitudes of Wednesday’s quakes were smaller. Japan’s temblor was 9.0-magnitude, about four times more powerful than Wednesday’s first quake. The 9.1-magnitude quake in 2004, which triggered an Indian Ocean tsunami that killed 230,000 people, was five times more powerful.
(Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)
