The seismogenic layer is the range of depths within the crust

Crust (geology)

In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...

 or lithosphere

Lithosphere

The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...

 over which most earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s are initiated. Typically in continental crust

Continental crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...

 this is in the uppermost 15 km. The base of this layer represents the downwards change in deformation mechanism from elastic and frictional processes associated with brittle faulting to a generally aseismic zone where ductile creep

Creep (deformation)

In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....

 becomes the dominant process. The location of this change in deformation style is sometimes referred to as the Brittle-ductile transition zone

Brittle-ductile transition zone

The brittle-ductile transition zone is the strongest part of the Earth's crust. For quartz and feldspar rich rocks in continental crust this occurs at an approximate depth of 13–18 km . At this depth rock becomes less likely to fracture, and more likely to deform ductilely by creep...

.