The December 26,2004 Indian Ocean earthquake was an undersea mega-thrust earthquake with an epicenter off
the west coast of Sumatra, Indonesia. The earthquake was caused by subduction along the Sunda Trench and
triggered a series of devastating tsunamis along the coasts of most landmasses bordering the Indian Ocean, killing
nearly 230,000 people in eleven countries, and inundating coastal communities with waves up to 30 meters high.
With a magnitude of 9.2, it is the second strongest earthquake ever recorded on a seismograph. There was a 8.6
earthquake three months later - now generally considered to be a separate event as opposed to an aftershock.
There has been technical speculation that the 8.1 earthquake on December 23 near New Zealand triggered the
December 26th event. Subsequent analysis has shown that the fault rupture that proceeded northwards towards
the Andaman and Nicobar Islands moved about 25% slower than the southwards rupture - a mere 2.1 km/s ( 7,600
km/h). People living around the Indian Ocean were relatively fortunate because the northern plate boundary is
where the fault type changes from subduction to strike-slip - the velocity of the water was reduced and the size of
the tsunami moving north was reduced. Most of the 1600 km fault rupture generated water movement so a
estimated total of 30 cubic kilometers (7 cubic miles) of water formed the basis of the waves. Converting the
surface energy released by the earthquake and tsunamis we have about 26 megatons of TNT or 1500 Hiroshima
bombs (minus the radiation and winds - 20% is just the tsunami). The event changed the shape of Planet Earth,
shortened the length of a day by almost 3 microseconds and changed how our planet spins on its axis. These
effects lasted about 4 months. Evidence from near Aceh shows that the wave reached a height of 25 m in many
places and up to 30 m in selected inland areas.
WHAT IF TWENTY-FIVE MEGATONS OF TNT
EXPLODED IN THE MALACCA STRAITS WITH
NO WARNING? |