noun
thrust fault
A geological fault where older rock is pushed over younger rock due to compressional forces.
この地域には衝上断層が多く見られる。
Many thrust faults are observed in this region.
逆断層 (reverse fault) is a broader category; 衝上断層 is a specific type of reverse fault with a low-angle dip (typically less than 45 degrees).
Compound of 衝上 (しょうじょう, 'thrust up') and 断層 (だんそう, 'fault'). The exact historical derivation is uncertain; the spelling is conventionally associated with the geological meaning.