Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Abstract (EDOC: 12963)
During the INDEPTH IV controlled-source seismic experiment in June 2007, 949 vertical-component seismographs (IRIS-PASSCAL Texans) at 100-650 m station spacing and 20 broadband and 29 short-period three-component seismographs (34 from GIPP, Germany and 15 from SEIS-UK) at 5-6 km station spacing recorded 5 large shots (1000-2000 kg) and 100 small shots (80 kg) along a 270 km long profile across the Kunlun mountains in northeast Tibet. A detailed tomographic inversion of the well-recorded Sg arrivals observed by these 998 instruments reveals the S-velocity structure of the upper crust down to about 10 km depth beneath the profile. The major lateral variation in upper crustal S-velocities along the profile is from lower velocities beneath the Qaidam basin in the north to higher velocities beneath NE Tibet in the south. Beneath NE Tibet, there are Seismik 229 also lateral variations with lower S-velocities beneath the valleys (basins) along which the North Kunlun and South Kunlun Faults run and higher velocities in the mountainous regions between and to the north and south, where older rocks are generally exposed at the surface. From the S-velocity model, there is no evidence within the upper crust for major overthrusting of NE Tibet over the Qaidam basin. P-wave reflections indicate that the Moho lies at about 50 km depth beneath the southern Qaidam basin and that further south prominent boundaries exist within the deep crust beneath the NE Tibetan plateau. Following the controlled-source experiment, 50 broadband seismographs (35 from GIPP, Germany and 15 from SEIS-UK) were deployed for a period of one year along two profiles across the Kunlun mountains and the Jinsha river suture in northeast Tibet.
(2009): Preliminary results form the Controlled-Source Seismic Experiment along the INDEPTH IV Transect from the NE Tibetan Plateau to the Qaidam Basin. 69. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (Kiel 2009), 228-229.