CONSTRAINTS ON THE CRUST AND UPPER MANTLE OF THE KYRGYZ TIEN SHAN FROM THE PRELIMINARY ANALYSIS OF GHENGIS BROAD-BAND SEISMIC DATA

Abstract

The Tien Shan is the best example of active intracontinental mountain building in the world. In order to determine how strain has accumulated in the range, a 28 station network was deployed in the Tien Shan during 1998-2000. Preliminary analysis of seismograms from this network showed two important results: first, P-SVwave conversions from the Moho reveal that the crust beneath the central Tien Shan is unusually thin, being no thicker than that beneath the Kazakh Shield to the north or the Tarim Basin to the south. Second, splitting of SKS-waves shows that the strain in the mantle is largely a passive response to north-south shortening and that this strain is imprinted on the mantle far to the north of the orogeny itself.