Deep deformation process of the NE Tibetan Plateau: evidence from receiver function imaging

Abstract

<p>The deformation of Qilian Orogenic Belt, which is the uplifting front of the northeastern Tibet Plateau, plays a decisive role in understanding the dynamic process of the area uplift. Many of the tectonic processes models of the Tibetan Plateau growth, which are based on geophysical and geological studies, have been conducted in recent years. However, the deformation mode of northeastern Tibetan Plateau (NETP) remains controversial for lack of sufficient proofs. We used teleseismic waveform data collected from the China Array seismic experiment during 2013-2015 and QL temporary stations during 2016-2017. In this study, we used the 3-D Common Conversion Point (CCP) technique (with the P/S receiver functions) to obtain detailed seismic velocity discontinuities structure of lithosphere beneath the NETP and Alxa block. Our preliminary results can be summarized as follows: 1) The Lithosphere asthenosphere boundary (LAB) lies at a depth pf 110-140 km in Alxa platform, deepens below the North Qilian mountain (160-170 km ) which has been inserted by lithosphere of Central Qilian, between the South Qilian suture zone (SQL) and the north of the Songpan-Ganzi Terranes (160-170 km). 2) The main features in the crust include offset of Moho beneath NQLF, shallower crust thickness below between the NQLF and LSSF and a continuous positive interface over the Moho in the north of the LSSF. 3) According to our observation and previous studies, we suppose that lithosphere had been passive underthrust and localized crust had been shortened and thickened in the NETP.</p>