The apparent wave propagation velocity is an important parameter which is used to calculate the strain in pipe induced by seismic waves.
To evaluate the axial strain in pipe, as a general rule, the velocity of shear wave (S-wave) is used for the sites within the epicentral distance of 5 times focal depth. In the other hand, the velocity of Rayleigh wave (R-wave) is considered for the sites having epicentral distance more than 5 times focal depth (Figure 7.1.2).