Conrad discontinuity

The Conrad discontinuity is a horizontal seismic boundary zone or surface in the non-orogenic continental crust at a depth of approx. 10–20 km, in which the speed of seismic P-waves jump from 6.5 km / s (below) to 5.6 km / s (above) changes.

The discontinuous change in wave speed at the Conrad discontinuity was first observed by the Austrian seismologist and climatologist Victor Conrad (1876–1962) in 1923. It has since been found in all continental blocks, but it is not a universal phenomenon and cannot be detected everywhere. With regard to the internal structure of the earth, it represents a common seismic definition of the boundary between the upper and lower continental crust. Deep continental boreholes (e.g. the continental deep borehole (KTB) in Germany and the borehole on the Russian Kola peninsula ) have no evidence a petrological anomaly within this boundary zone. At this depth (10–20 km) the rocks of the continental crust are usually in the metamorphic amphibolite facies .

The Conrad discontinuity is less studied in the geosciences than the Mohorovičić discontinuity , the seismic interface between the earth's crust and mantle .

literature

• V. Conrad (1925): Time curves of the Tauern earthquake on Nov. 28, 1923 . Announcements from the Earthquake Commission, Academy of Sciences Vienna, New Series 59: 1–23.