GEOLOGY

Detailed explanation-1: -seismograph, instrument that makes a record of seismic waves caused by an earthquake, explosion, or other Earth-shaking phenomenon.

Detailed explanation-2: -A seismogram is a record of the ground motions caused by seismic waves from an earthquake. A seismograph or seismometer is the measuring instrument that creates the seismogram.

Detailed explanation-3: -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-4: -The visual record produced by a seismograph is called a seismogram.