Seis'mal or Seis'mic, a.

a. [From Gr. σεισμός, earthquake, from σείειν, to shake.] Of, or pertaining to, an earthquake. “The seismic area, the tract on the earth’s surface within which an earthquake is felt.” Bragley.

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. Bragley.