What determines the size of a tsunami?

For tsunamis that are generated by underwater earthquakes, the amplitude of the tsunami is determined by the amount by which the sea-floor is displaced. Similarly, the wavelength and period of the tsunami are determined by the size and shape of the underwater disturbance.

What affects the size of a tsunami?

The amount of movement of the ocean floor, the size of the area over which it occurs (which may be reflected in how long the earthquake lasts), and the depth of the water at its source are all important factors in the size of a resulting tsunami.

What determines how strong or large a tsunami will be?

The longer an offshore earthquake lasts, the more likely it will produce a strong tsunami. The length of the shaking is related to the length of the rupture; the longer the shaking, the longer the rupture. A magnitude 7 earthquake might rumble for 20-40 seconds.

How are tsunamis size measured?

Tsunamis are detected and measured by coastal tide gages and by tsunami buoys in the deep ocean. The tide gages measure the tsunami wave directly. In the deep ocean, sensors on the ocean floor detect the pressure signature of tsunami waves as they pass by.

Why are some tsunamis bigger than others?

Tsunami waves grow higher and steeper as they move from deep water into shallower water. The deeper the water where they start, the more their heights increase as the waves approach the shore.

Why do tsunami waves get bigger?

In deep water, a tsunami moves very fast and has a long wavelength and a small amplitude. As it enters shallower water, it slows down and the wavelength decreases. This causes the wave to become much taller. As waves slow down, they start to bunch together, so they have a shorter wavelength than before.