Why can a tsunami cause damage far from the earthquake that created it?

A tsunami can cause significant damage far from its point of origin because it functions as a train of progressive, oscillatory waves capable of traveling across entire ocean basins at high speeds.1

In the deep ocean, these waves travel as fast as 800 km (500 miles) per hour. While they possess enormous wavelengths—sometimes exceeding 500 km—their amplitudes (heights) are very small, typically only 30 to 60 cm. Because of these characteristics, tsunamis are often imperceptible to ships in the open sea.21

The destructive potential is realized only as the waves approach a coast. Friction with the rising sea bottom slows the waves, causing their wavelengths to shorten and their amplitudes to increase dramatically. This process, where fast-moving water from the open ocean stacks onto slower-moving water near the shore, can result in waves rising as high as 30 meters (about 100 feet) above normal sea level. Consequently, coastal areas thousands of kilometers away from the initial earthquake can experience severe inundation and destruction.31245