Thrustförkastning

Thrustförkastning, a term originating from Swedish geology, describes a specific type of fault where the footwall has moved up relative to the hanging wall. This movement is predominantly in the direction of the fault's dip. In essence, it is a reverse fault with a dip angle greater than 45 degrees. The term "thrust" refers to the overriding motion, where the upper block is pushed up and over the lower block.

These faults are characteristic of compressional tectonic regimes, often found in areas where tectonic plates are colliding or shortening. The immense forces involved can cause significant crustal shortening and thickening. In thrust faulting, rocks are stacked on top of each other, leading to the repetition of geological layers in cross-section. This stacking can create complex geological structures and significantly alter the landscape.

Thrustförkastning can occur over a wide range of scales, from small, localized features to vast, mountain-building systems like the Himalayas or the Alps. Identifying and understanding thrust faults is crucial for geological mapping, resource exploration (such as oil and gas deposits which can be trapped by these structures), and seismic hazard assessment, as they can be active sources of earthquakes. The distinction between a thrust fault and a normal fault lies in the direction of relative block movement and the prevailing tectonic forces.