GEOLOGY

Detailed explanation-1: -Both P and S waves travel outward from an earthquake focus inside the earth. The waves are often seen as separate arrivals recorded on seismographs at large distances from the earthquake. The direct P wave arrives first because its path is through the higher speed, dense rocks deeper in the earth.

Detailed explanation-2: -Because P waves are the fastest seismic waves, they will usually be the first ones that your seismograph records. The next set of seismic waves on your seismogram will be the S waves. These are usually bigger than the P waves.

Detailed explanation-3: -P waves are recorded earlier than S waves, because they travel at a higher velocity. SF Table 7.1 shows that P waves have a higher velocity than S waves when traveling through several mineral types. The speed at which seismic waves travel depends on the properties of the material that they are passing through.

Detailed explanation-4: -When an earthquake occurs, two main types of vibratory waves move through the body of the earth from the point of fracture. The primary, or P, waves travel most quickly and are the first to be registered by the seismograph.