Publication Date:
2020-02-12
Description:
The Pamir and Hindu Kush seismic zones, at the northwest corner of the India-Asia collision zone, are unique in that they are the only seismic zones in the heart of a continent with deep earthquakes at 90 to 250 km depth. Since 2008, the GFZ has operated several temporary seismological networks in the central Asian region in Tajikistan, Kyrgyzstan and most recently Afghanistan, together with local partners. The aims of these experiments have been to try to understand these deep seismic zones and to elucidate the crustal and mantle structure beneath the region. To date, the analysis of the seismological data shows that under the Pamir, the cold Asian mantle lithosphere descends (subducts), together with the lower crust and a part of the overlying middle crust, in a strongly curved, cone-shaped arc. At about 90 to 100 km depth, the middle crust detaches from the lower crust, pools and subsequently either stays there or rises back towards the surface due to its buoyancy. Only the lower crust descends completely to greater depths. Mineral reactions within the lower crust are most probably responsible for the deep earthquakes. Thus, in answer to the question posed by the title, only the lower continental crust seems able to descend (subduct), together with the continental lithospheric mantle, back deep into the Earth. The bulk of the crust (i.e. the upper and middle crust) remains at crustal levels and contributes to crustal thickening and mountain building.
Language:
German
Type:
info:eu-repo/semantics/article
Format:
application/pdf
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