Seismic anisotropy of the upper mantle in Ningxia region

Abstract: A polarization analysis has been carried out on teleseismic SKS phases with epicentral distance between 85deg;and 110deg;and from Mge;6.0 earthquakes recorded by 6 digital broadband seismic stations with 3 components in Ningxia region, China. The splitting parameters have been obtained by using the SilverChan methodand the anisotropy feature of the upper mantle in Ningxia region has been obtained. The result shows that in Ningxia region there widely exists the upper mantle anisotropy.The anisotropy beneath the Erdos block, where the YCI station is located, could be classified as fossil anisotropy, while the anisotropy in other regions reflects tectonic movement undergoing, having also provided the deep evidence about the complex kinetic figure of the Helanshan Mountain and its double sides. Finally, it is inferred that in this region the movement between the crust and upper mantle from the northeast edge of the Qingzang Plateau to the Alashan Block and the Yinchuan broken region is coupled, and the Erdos Block region has not been clear yet.