Moho properties of western Ordos block and surrounding regions constrained by teleseismic receiver functions and its tectonic implication

Based on the teleseismic records of Himalaya-II broadband seismic array with 129 stations across the Ordos block along north-south direction, 20267 teleseismic P-wave receiver functions have been obtained. We extracted the stable arrival time of P-to-S conversion and multiple reverberations by stacking the receiver functions in the bins with closed pierce points of PMs phase, and then calculated the crustal thickness and velocity ratio across the north-south section of western Ordos block. Meanwhile, the velocity and density contrast of the Moho beneath partial stations have been determined with grid searching stack technique. The results indicated that the crust is thin with low velocity ratio (1. 66 similar to 1. 72) and relatively small density contrast of (4%similar to 10%) below the Qinling-Weihe graben, which imply the crust in this area is mainly composed of felsic acidic rocks. The crust of southern Ordos is thicker (41. 4 +/- 1. 3 km) with higher velocity ratio and smaller velocity contrast of (14%similar to 23%) , which might have been caused by the compression of the Tibetan Plateau. The velocity ratio is obviously higher than 1. 87 with larger velocity contrast of (19%similar to 29%) and smaller density contrast beneath northern Ordos. We speculated that the lower crust of northern Ordos has experienced the partial melting, the higher velocity ratio may be caused by the combination of partial melting and sedimentary layers.