secondary wave

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Cross-sectional diagram of Earth showing how S-waves and P-waves from an earthquake travel through the planet's layers, with S-waves stopping at the liquid outer core and P-waves bending as they pass through the solid inner core, creating shadow zones.

The types of seismic waves explained

How S waves travel

secondary wave

seismology

Also known as: S wave, S-wave

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July 15, 2026

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Cross-sectional diagram of Earth showing how S-waves and P-waves from an earthquake travel through the planet's layers, with S-waves stopping at the liquid outer core and P-waves bending as they pass through the solid inner core, creating shadow zones. — earthquake: P waves and S waves P and S waves travel through the planet Earth after an earthquake. Scientists studying the waves produced by earthquakes learned that Earth's core has separate liquid and solid layers. S waves do not travel through liquid, but P waves do. A simplified diagram shows the S waves on the left and the P waves on the right, but waves of both types would actually radiate in all directions.

In seismology, an S wave, or secondary wave, is a type of seismic wave that travels through the Earth's body. These waves are generated by earthquakes or other energetic sources and are characterized by a shear motion, where particles move perpendicular to the direction of wave propagation. Unlike primary (P) waves, S waves can only travel through solid materials because liquids cannot sustain shear stress. They propagate at a slower speed than P waves, meaning they reach seismic recording stations after the P waves. The study of S waves, along with other seismic waves, provides crucial information about the Earth's internal structure, including the liquid nature of its outer core.123

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seismic wave
…recording station faster than the secondary, or S, wave. P waves, also called compressional or longitudinal waves, give the transmitting medium—whether liquid, solid, or gas—a back-and-forth motion in the direction of the path of propagation, thus stretching or compressing the medium as the wave passes any one point in a…
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…recording station faster than the secondary, or S, wave. P waves, also called compressional or longitudinal waves, give the transmitting medium—whether liquid, solid, or gas—a back-and-forth motion in the direction of the path of propagation, thus stretching or compressing the medium as the wave passes any one point in a…
Read More

earthquake
Principal types of seismic waves
…type of body wave, the S wave, travels only through solid material. With S waves, the particle motion is transverse to the direction of travel and involves a shearing of the transmitting rock.
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…type of body wave, the S wave, travels only through solid material. With S waves, the particle motion is transverse to the direction of travel and involves a shearing of the transmitting rock.
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Earth exploration
Seismic refraction methods
…body: P waves (primary) and S waves (secondary). P waves are compressional waves and travel at the highest velocity; hence, they arrive first. S waves are shear waves that travel at a slower rate and are not able to pass through liquids that do not possess shear strength. In addition,…
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…body: P waves (primary) and S waves (secondary). P waves are compressional waves and travel at the highest velocity; hence, they arrive first. S waves are shear waves that travel at a slower rate and are not able to pass through liquids that do not possess shear strength. In addition,…
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infrasonics
…of earthquake waves exist: the S-wave, a transverse body wave; the P-wave, a longitudinal body wave; and the L-wave, which propagates along the boundary of stratified mediums. L-waves, which are of great importance in earthquake engineering, propagate in a similar way to water waves, at low velocities that are dependent…
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…of earthquake waves exist: the S-wave, a transverse body wave; the P-wave, a longitudinal body wave; and the L-wave, which propagates along the boundary of stratified mediums. L-waves, which are of great importance in earthquake engineering, propagate in a similar way to water waves, at low velocities that are dependent…
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seismograph
Applications of the seismograph
… in the direction of propagation), S waves (transverse waves—that is, waves that vibrate at right angles to the direction of propagation), and surface waves (compression waves with no vertical or longitudinal components). In the case of distant earthquakes or of nearby very large earthquakes, the seismogram pattern is more complicated…
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… in the direction of propagation), S waves (transverse waves—that is, waves that vibrate at right angles to the direction of propagation), and surface waves (compression waves with no vertical or longitudinal components). In the case of distant earthquakes or of nearby very large earthquakes, the seismogram pattern is more complicated…
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