The P-wave gets progressively farther ahead of the S-wave as they travel through Earth’s crust.

P-waves have speeds of 4 to 7 km/s, and S-waves have speeds of 2 to 5 km/s, but both are faster in more rigid materials. Both components of earthquakes travel more slowly in less rigid materials, such as sediments. During earthquakes, the speed of P-waves in granite is significantly higher than the speed of S-waves. These two types of waves propagate at different speeds, and the speed at which they travel depends on the rigidity of the medium through which they are traveling. The longitudinal waves in an earthquake are called pressure waves (P-waves) and the transverse waves are called shear waves (S-waves). The waves under Earth’s surface have both longitudinal and transverse components. Surface earthquake waves are similar to surface waves on water. Geologists rely heavily on physics to study earthquakes since earthquakes involve several types of wave disturbances, including disturbance of Earth’s surface and pressure disturbances under the surface. (Petty Officer 2nd Class Candice Villarreal, U.S. The Richter scale rating of earthquakes is related to both their amplitude and the energy they carry. However, as mentioned in the text feature on surfing, actual ocean waves are more complex than this simplified example.įigure 13.9 The destructive effect of an earthquake is a palpable evidence of the energy carried in the earthquake waves. Instead, the seagull bobs up and down in place as waves pass underneath, traveling a total distance of 2 X in one cycle. It is important to note that this movement of the wave is actually the disturbance moving to the right, not the water itself otherwise, the bird would move to the right. Its amplitude X is the distance between the resting position and the maximum displacement-either the crest or the trough-of the wave. In the figure, the wave itself moves to the right with a wave velocity v w. The time for one complete up-and-down motion is the simple water wave’s period T.

The wavelength can also be thought of as the distance a wave has traveled after one complete cycle-or one period. Its wavelength is the distance from crest to crest or from trough to trough. Wave velocity is sometimes also called the propagation velocity or propagation speed because the disturbance propagates from one location to another.Ĭonsider the periodic water wave in Figure 13.7. The wave velocity v w v w is the speed at which the disturbance moves. The wavelength λ λ is the distance between adjacent identical parts of a wave, parallel to the direction of propagation. In addition to amplitude, frequency, and period, their wavelength and wave velocity also characterize waves.

Period-time it takes for one wave cycle to complete.

Frequency-number of waves passing by a specific point per second.Amplitude-distance between the resting position and the maximum displacement of the wave.However, it is helpful to word the definitions in a more specific way that applies directly to waves: Period-time it takes to complete one oscillationįor waves, these variables have the same basic meaning.Frequency-number of events per unit of time.Amplitude-maximum displacement from the equilibrium position of an object oscillating around such equilibrium position.In the chapter on motion in two dimensions, we defined the following variables to describe harmonic motion: Review amplitude, period, and frequency for simple harmonic motion.

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