SANDWICH: A 2D Broadband Seismic Array in Central Tibet

The tectonic processes that formed the Tibetan plateau have been a significant topic in earth science, but images of the subducting Indian continental lithosphere (ICL) are still not clear enough to reveal detailed continental collision processes. Seismological methods are the primary ways to obtain images of deep crust and upper-mantle structures. However, previous temporary seismic stations have been unevenly distributed over central Tibet. The Institute of Geology and Geophysics, Chinese Academy of Sciences, has initiated a 2D broadband seismic network in central Tibet across the Bangong-Nujiang suture to fill in gaps among earlier north-south linear profiles for the purpose of detecting the lateral variation of the northern end of the subducting ICL. The health status for each station has been checked at each scheduled service trip. The noise level analysis shows a quiet background in central Tibet, with low cultural noise. Preliminary earthquake locations indicate that they are crustal and broadly distributed rather than only occurring along major faults, suggesting a diffused deformation in the conjugated strike-slip fault zone. Preliminary receiver function analysis shows a complicated crust with significant east-west lateral variations.