Short answers, pulled from the story.
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less from the horizontal. This shallow angle distinguishes it from other reverse faults and allows massive slabs of rock to slide over vast distances horizontally.
Archibald Geikie coined the term thrust-plane in 1884 to describe these special faults. He noted that the rocks on the upthrown side had been pushed horizontally forward, overturning centuries of established geological theory.
The destructive 1994 earthquake in Northridge, California, was caused by a previously undiscovered blind thrust fault that had never broken the surface. This fault plane terminates before reaching the Earth's surface, making it exceptionally difficult to detect during mapping.
Large overthrust faults are the primary architects of the world's great mountain ranges including the Himalayas, the Alps, and the Appalachians. These structures form in tectonic environments where two continental plates collide and produce orogenic belts that can thicken the crust by up to 200%.
A thrust fault is defined by its shallow angle dipping no more than 45 degrees from the horizontal. When the angle drops below 15 degrees and the displacement stretches for kilometers, the structure earns the specific designation of an overthrust.