Seismic Waves

Study Notes

P waves are the fastest type of seismic waves, arriving first at seismic stations after an earthquake, with speeds between 5-8 km/s.
P waves are compressional waves, causing particles to move back and forth in the same direction as the wave is traveling.
P waves can travel through solids, liquids, and gases.

S waves are slower than P waves, arriving at seismic stations after P waves, with speeds ranging from 3-4.5 km/s.
S waves are shear waves, causing particles to move perpendicular to the direction of wave propagation.
S waves can only travel through solids and cannot pass through liquids or gases.

Longitudinal waves, also known as surface waves, travel along the Earth's surface rather than through its interior.
There are two main types: Love waves, causing horizontal shearing of the ground, and Rayleigh waves, producing a rolling motion.
Surface waves generally have lower frequencies and travel slower than P and S waves, but can cause more extensive damage due to their larger amplitude and longer duration.

The exact speeds of seismic waves can vary depending on the material they are traveling through.
When P waves pass through the Earth's crust, they cause particles to move back and forth in the same direction as the wave is traveling, resulting in alternating regions of compression and rarefaction.
When S waves pass through the Earth's crust, they cause particles to move perpendicular to the direction of wave propagation, resulting in a shaking effect.

S waves cannot travel through liquids because their shear motion requires a medium that can support shear stress.
P waves arrive first at a seismic station, followed by S waves, and then the slower surface waves (long waves).
Seismologists use the difference in arrival times between P waves and S waves at various seismic stations to determine the distance to the earthquake's epicenter.

Analysis of long waves provides information about the earthquake's magnitude and the nature of the Earth's surface materials.
Surface wave analysis can reveal details about the Earth's crust and upper mantle structures.
Understanding the characteristics of long waves helps in assessing the potential impact on buildings and infrastructure.