Home – Home – Jornals – Russian Geology and Geophysics 2003 number 6

Upper mantle beneath the Alpine-Himalayan orogen (AHO) at depths from 100 to 500 km has been studied using ITS inversion of teleseismic P travel times from earthquakes that occurred in the region and were recorded by the worldwide seismological network (ISC bulletins). 3D velocity maps were obtained as a sum of independent inversions in about sixty overlapping blocks 600-1000 km across. This approach is similar to high-frequency spatial filtration and provides a much higher resolution than the global tomography. High-velocity zones within the orogen have been interpreted as signature of continental or oceanic lithosphere sinking to the upper mantle under active regional compression. The maps show well pronounced traces of subduction in the regions of Cretan arc, Hindukush, and Burma, also confirmed by independent data, as well as other less certain evidence of subduction. Positive anomalies in the western part of the orogen are attributed to subduction in the area of Cyprus and along the Caucasus-Kopet Dagh-Lut belt. The lithosphere of the Indian plate subducted beneath the Himalayas and Tibet has a rather complicated structure. Zones of sinking lithosphere are traceable around the Tarim block. Distinct low-velocity anomalies in Mongolia, Tibet, and Southern Caspian basin may be produced by active mantle plumes.