\Seis"mic\, Seismal \Seis"mal\, a. [Gr. seismo`s an
earthquake, from sei`ein to shake.]
Of or pertaining to an earthquake; caused by an earthquake.

{Seismic vertical}, the point upon the earth's surface
   vertically over the center of effort or focal point whence
   the earthquake's impulse proceeds, or the vertical line
   connecting these two points.