Definition of upthrown:
(n) :
(geology) A fault in which a mass of material has been thrown up from below.
(v) :
(geology, transitive) To throw up (a mass of material) from below, causing a fault.
(v) :
(geology, intransitive, of a mass of material) To be thrown up from below, causing a fault.
(v) :
(archaic, poetic) To throw or cast upwards.