Question

what are the 2 subtypes of seismic wave??

Answer 1

the two different types of seismic waves are:
Compressional and shear.

Answer 2

here are four main types of seismic waves, each characterised by its specific particle motion:

1.Compressional or “p” waves are identical to sound waves – the particle motion is parallel to the propagation direction:

2.Shear or “s” waves are characterised by particle motion that is perpendicular to the propagation direction:.

Taken collectively, p- and s-waves are known as “body” waves. The velocities of both can be measured via seismic refraction.

3.Surface waves, as the name implies, travel primarily along the ground surface; amplitudes decrease rapidly with depth. There are two types of surface waves. Like body waves, they are characterised by particle motion.

In the near surface, this motion is “retrograde”, meaning that it is counter-clockwise when the propagation is left-to-right. At depth, the motion can reverse to pro grade.

4.Particles affected by "Love" waves vibrate perpendicular to the propagation direction: