Seismic Structure Of The Kunlun Stike-Slip Fault Using INDEPTH IV Active-Source Dataset, North Tibet

Two-dimensional active-source seismic reflection/refraction data is used to study the strike-slip Kunlun Fault system in northeastern Tibet. Collision of the Eurasian and Indian plates 53-58 mya resulted in uplift and thickening of the Tibetan crust to approximately 80 kilometers. Strike-slip faults in the plateau, including the Kunlun strike-slip, accommodate east-west extension and escape of lithospheric material from the central plateau. The INDEPTH IV dataset was collected as part of Project INDEPTH (International Deep Profiling of Tibet and the Himalaya), a multi-year international collaborative effort to study the crustal structure of the Tibetan Plateau and better understand its evolution. INDEPTH IV active-source data was collected in the summer of 2007 over a 270 km transect that crossed the Kunlun Mountains and Qaidam Basin north of the range. Active sources were five large (1000-2000 kg) explosions and 110 small explosions ( 80-200 kg) explosions across the central 100 km of the line. Seismometers included 950 Reftek Texans (100 to 650-m spacing) and a 1000-channel cabled Sercel unit (50-m spacing). We processed and stacked the Texan data into low-fold CMP stacks and then interpreted those stacks. In particular, we are examining the lateral extent of deformation associated with the Kunlun strike-slip fault, which we hypothesize should have lower seismic velocities than the surrounding rock and display a higher degree of seismic anisotropy. Seismic anisotropy can be an important indicator of mineral grain alignment and stress fields associated with fault zones. We also examine the later times of our CMP stacks and shot gathers to determine whether we see reflections from the Lithosphere-Asthenosphere Boundary (LAB), as others have observed in New Zealand.