Tsunami formation
Tsunami formation is quite complex. The size and energy of the
wave are related to the earthquake’s magnitude and depth, water
depth where the quake occurs, the amount of vertical motion of the
sea fl oor, the velocity of that motion, and the effi ciency with which
energy is transferred from the earth’s crust to ocean water.
What is the diff erence between velocity and speed?
Do you know what engineers mean by effi ciency?
When an earthquake happens under water, the ocean fl oor can
drop (or rise) very suddenly. In a megathrust earthquake, the displacement
can be extremely large and occur over the entire length
(sometimes more than 1000km) and width of a fault. Energy is
transferred to the water both from the shaking of the earth and the
sudden rise or fall of the sea fl oor.
Why would a drop or rise in the sea fl oor
transfer energy to water?
The December 26, 2004 earthquake in the Indian Ocean dropped millions, possibly billions, of cubic meters of water
by about 15 m. In other words, in a very short period of time, the water went from having billions and billions of
joules of potential energy, to having billions and billions of joules of kinetic energy. This energy is what spreads out
from the source and across the ocean to form the tsunami wave.
What is the diff erence between potential and kinetic energy?
Even though tsunamis are big waves, in deep water their size is
hidden in the ocean depths. Crests may be a meter high or smaller
and separated by 100 kilometers or more, but they are also moving
extremely fast, sometimes more than 500 kilometers per hour. as
fast as a transcontinental airplane. Tsunamis don’t get large until
they get close to shore.
Posted by Aneka Tips
on 17.05. Filed under