Fault (geology)

A fault ( broken, jump, shift or disturbance in the narrow sense ) is a tensile or fracture in the rock, to a few dozen or hundred kilometers two areas of rock or crustal components displaced over distances of centimeters range up against each other. The offset is referred to as jump height and jump distance. During the term disorder is also a plastic deformation of the rocks may include with, only the result of a rock fracture is called a fault.

The formation of dislocations is usually accompanied with earthquakes and is often linked to old -scale weak zones of the earth's crust. This weakness zones determine the mechanism of the oven process. But it may also be due to seismic shock waves Impakten.

With a rejection always go hand in hand distinct divisions, such as clefts and crevices in which to smooth by the friction of the rocks against each other, sometimes reflecting surfaces with motion grooves can form ( the so-called armor ). The rocks can be crushed in the warp fields to mylonites and tectonic breccias.

When undigested, still active faults, the type of fault can also be determined with the help of the fault plane solution.

Classifications

Classification according to the direction of thrust

A distinction is usually the following types of faults:

• Normal faults ( normal faults ) caused by lateral expansion of the rock packages
• Reverse faults or thrust faults ( inverse warping ) arise in lateral compressibility
• Slip faults (transverse, horizontal or lateral shifts ) arise in lateral balance movements, mostly along steeply dipping fault planes.
• Lid fissures are shallow fault planes without causing a particular movement direction is determined.

In reality, the fault described species rarely occur in pure form. Most are hybrids of two, sometimes encountered even out of all three forms.

Classification according to the stratification

Furthermore, distortions differ in their angles to the dip of the rock stratification:

• Antithetic faults have a dip against the stratification.

Fault systems

Several, approximately parallel dislocations next to each other form rejection systems such as the relay breaks the so-called. Against Radical incident ended dislocations can form clumps or trenches, ie the fault planes strive for depth away from each other or towards each other.

A fault is in nature often difficult to recognize because it is usually either a ceiling or weathering the jump height has been leveled by erosion. Only in relatively recent turmoil the individual floes still occur as morphological fracture stages in appearance. As an indication of a fault can leaking water at the so-called fault sources - a special form of artesian springs - serve. These sources arise when a distance greater water marveling be pushed next to water permeable rocks. Dislocations are also visible seized at the different weathering rocks next to each other. Sometimes, contrary to expectations, not the raised soil eroded as morphological survey out, but the sunken, so long as it is for the latter to more resistant layers are (relief reversal).

Is on the geological map of the relative displacement sense of vertical faults ( up, over, normal faults ) based on the different ages of the adjacent rock layers visible. Older layers on a wing of the disorder are lifted relative to the layers of the opposite wing and the younger layers were relatively lowered.

Hydrogeology and volcanism

Along the weakness zone of the fault may magmatic material penetrate up, cover the wide areas or can build volcanoes. The residual in the clefts magma solidifies to form dikes. In open columns but can also hydrothermal solutions rising from the depths or infiltrating surface water. The dissolved minerals can in this case be precipitated and be deposited on the gap walls in the form of mineral transitions. With sufficient amount of arable ores this can lead to the formation of vein deposits.

Fault zone

A fault zone is, as the name implies, only a rejection, a cut in the earth's crust that runs between the other two types of tectonic elements. Most fault zones are located on the apex of the mid-ocean ridge, a few between a back and a subduction zone; even less extend from one subduction zone to another. The earthquakes on faults of back to back are quite superficial (in 1 km, 5 km depth ), since there the crust is still young and weak. However, where fault zones penetrate older crust, earthquakes can occur at a depth of 10 km up to 20 km. The most famous fault zone is the San Andreas Fault.

Digestion of dislocations

Whether a fault deferment or a removal has taken place, is sometimes difficult to decide. The main reason for this is that over time the deferred or above remaining portion of the warp has been eroded ( a plane ). Below show 4 images, such as the pattern of the digestion left and right of the line of fracture usually shows. A simple rule can be helpful for interpretation.

Image 2

Picture 3

Picture 4

The hand rule for simplification is that your hands are in the direction of the falling layers and the upper hand represents the upper part of the fault. Once the layers of information moves away from the body ( to the finger tips of the upper hand), the other time he moves approach ( to the wrist of the top hand). In this way can be known at the direction of falling of ( different ages ) layers easily determine whether it is ( engl. fault normal / reverse) to a deportation or deferment is.