P wave 5
P wave 5 :
A symbol for a seismic body wave that involves particle motion (alternating compression and dilatation) in the direction of propagation. P waves travel faster than S waves and, therefore, arrive earlier in the record of a seismic event (P stands for unda prima = primary wave). The particle displacement associated with P waves (for a classical linear elastic continuum in an isotropic far field) is parallel to the direction of wave propagation. For this reason, P waves are sometimes called longitudinal waves. See Chapter 2 in this Manual and Aki and Richards (2002 or 2009, p. 122). In isotropic media, the curl of the P-wave field (i.e., rotational motion) is zero. However, this is not so in general, for instance, for anisotropic or Cosserat continua. For this and other such symbols used in seismic phase names see IS 2.1 in this Manual and Storchak et al. (2003 and 2011)
