The Lithospheric Structure beneath the West and the South Ordos Block, China, from S Wave Receiver Functions

From recent GPS studies, referring the Siberia plate, the northeast China (including Ordos) moves 2~8 mm/a eastward, and the west part of China moves fast eastward (~20mm/a). The west side of Ordos is in the compressional tectonic environment, which differs from the east side of Ordos in the extensional tectonic environment. And Ordos block is rigid and relatively stable. We infer that it is the border of the different tectonic environments and this distribution of the tectonic pattern is dominated by the deep structure of Ordos. Hence, we have carried out several periods of broadband seismic observation across the west and the south margin of Ordos, and applied S wave receiver functions to analyze the lithospheric structure. We obtained two CCP stacking profiles, one of which crosses the west margin (Liupan mountain) and the other crosses then south margin of Ordos (Shanxi graben). We note that there are two negative phases at the depth of ~140km and ~280km beneath central the Ordos block. The shallower one drops down and the deeper one rises across Liupan Mountain. In the other direction, the significant two negative phases in the Ordos block become untraceable beneath Shanxi graben. There are another two negative phase at the depth of ~100km and ~320km beneath the Qinling Oregon to the south of Shanxi graben. And several wake phases are traceable beneath Qinling Oregon. (Supported by National Natural Science Foundation of China, Grant No: 40474017 40634021)