Seismic evidence for a Moho offset and south-directed thrust at the easternmost Qaidam-Kunlun boundary in the Northeast Tibetan plateau

During 2006 to 2007, a small array of broadband seismic stations was deployed across the eastern Qaidam-Kunlun border. Receiver functions derived from this data set show a coherent P-to-S converted phase from the Moho at similar to 65 km to similar to 58 km below sea level (b.s.l.) from south to north beneath the Kunlun mountains. The Moho is observed at similar to 45 km b.s.l. beneath the Qaidam basin. A sharp offset of similar to 15 km in the Moho depth is observed just beneath the Qaidam-Kunlun border. The close correlation between the surface topography and the sharp Moho offset substantiates the view that the Kunlun crust is weaker than that of the Qaidam basin and thickens vertically in response to compression between India (through the Tibetan plateau) and the Qaidam basin. Furthermore, a strong steeply north-dipping converted phase can be seen from similar to 5 to 15 km b.s.l. north of the North Kunlun Fault, which is likely a major south-directed thrust fault partially responsible for the thickening of the Kunlun crust. (C) 2009 Elsevier B.V. All rights reserved.