from
The Collaborative International Dictionary of English v.0.48
Earthquake \Earth"quake`\, n.
A shaking, trembling, or concussion of the earth, due to
subterranean causes, often accompanied by a rumbling noise.
The wave of shock sometimes traverses half a hemisphere,
destroying cities and many thousand lives; -- called also
{earthdin}, {earthquave}, and {earthshock}.
[1913 Webster]
{Earthquake alarm}, a bell signal constructed to operate on
the theory that a few seconds before the occurrence of an
earthquake the magnet temporarily loses its power.
[1913 Webster]