1. Earthquake waves are conventionally identified using letters to designate the nature of the wave over various legs of their travel path; see earthquake seismology and Figures W-7 and E-2. A Jeffreys-Bullen chart (Figure J-1) shows the normal arrival time for various types of waves. See also T-wave, H-wave, and C-wave. 2. Guided electromagnetic waves are classified as TE, TM, or TEM to indicate that the electric or magnetic field or both have transverse components only.