Question

Which of the following is the correct relation between the speeds of different types of seismic waves?

• A. Primary wave $<$ Secondary wave $>$ Surface wave.
• B. Primary wave $>$ Secondary wave $>$ Surface wave.
• C. Primary wave $=$ Secondary wave $=$ Surface wave.
• D. Primary wave $<$ Secondary wave $<$ Surface wave.

Answer 1

The correct option is B Primary wave $>$ Secondary wave $>$ Surface wave.

Seismic waves are of three types:

• Primary waves that travel the fastest and are the first to be recorded in a seismograph.
• Secondary waves that travel with speed lesser than that of the primary waves.
• Surface waves that travel with the lowest speed and are propagated over the earth's surface. These waves are responsible for the major damage caused in an earthquake.

So the order of their speeds would be Primary wave $>$ Secondary wave $>$ Surface wave.