ˈ ̷ ̷ˌ ̷ ̷ noun
Usage: often attributive
Etymology: Middle English erthequake, from erthe earth + quake
: a shaking or trembling of the earth that accompanies mountain building or other crustal movements including those caused by deposition of heavy loads of sediment on the sea bottom; that usually has an actual double amplitude of vibration of less than one millimeter, though a range of 76 millimeters is on record and the amplitude is commonly increased in unconsolidated surface material; and that is divisible into the two major classes volcanic and tectonic according to the major precipitating factor — see aftershock , focus 7, foreshock