ii) P or Primary waves
iii) S or Secondary waves
iv) L or long waves
The vibrations that are set up when an earthquake propagated as number of different types of waves. Different types seismograph are designed to record these waves, and seismological stations equipped with various types of seismograph have been set up all over the world. A major shock recorded by seismograph and its epicenter, time of origin, depth of focus, magnitude etc.