Is a tsunami an aftershock

Answer 1

Aftershocks take place in the ground. They are smaller quakes that follow major earthquakes.

Wikipedia: "Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami."

In subduction zones, the scraping lithosphere can form a ridged springboard that is loaded by the subducting lithosphere. When the load is enough to overcome the friction of subduction, it can unload within minutes causing massive earthquakes along the fault. When this happens under water, it can cause tsunami to accompany the earthquake.

A tsunami is the landfall byproduct of a large pressure wave propagating through a body of water. An underwater landslide (which can be caused by an earthquake or aftershock) will create a pressure wave as the mass of the landslide moves from one location to another. As the mass is in motion, the pressure of the water in front of the mass is increased while the pressure of the water behind the mass is decreased. The whole body of water this is taking place in reacts by back filling the mass in motion. This causes the propagation of a pressure wave away from the source.

When the wave is traveling through the ocean, the volumn of the whole body of water is so much greater than the relativly small amount of water involved in the wave propagation, that the variation in height at the surface is relativly shallow. The propagating wave can be seen, but it takes a very high point of view with very sensitive height measuring instruments.

Answer 2

Yes. There are always aftershocks after an earthquake, although some are too faint to feel. Over 700 aftershocks were recorded after the 2004 earthquake