Chapter 14, Problem 86PP

Tsunamis are ocean waves generally produced when earthquakes suddenly displace the ocean floor, and with it a huge volume of water. Unlike ordinary waves on the ocean surface, a tsunami involves the entire water column, from surface to bottom. To a tsunami, the ocean is shallow—and that makes tsunamis shallow-water waves, whose speed is $v=\sqrt{gd}$, where d is the water depth and g the gravitational acceleration. Tsunamis can travel thousands of kilometers across an ocean to reach the shore with their initial energy nearly intact; when they do, they can cause massive damage and loss of life (Fig. 14.39).

FIGURE 14.39 People flee as the devastating tsunami of December 2004 strikes Thailand (Passage Problems 81-84).

On the open ocean, a tsunami has relatively small amplitude—typically 1 m or less. As the tsunami approaches shore, its amplitude increases and its wavelength decreases. As a result,

1. a. its total energy increases.
2. b. the rate at which it carries energy shoreward increases.
3. c. the wave frequency increases.
4. d. none of these quantities changes.