Small Branches of Possible Crustal Flow in SE Tibetan Plateau Revealed by High-Resolution Attenuation Tomography with Chinarray Lg Data

Session: Recent Development in Ultra-Dense Seismic Arrays With Nodes and Distributed Acoustic Sensing (DAS)
Type: Oral
Date: 4/30/2020
Time: 02:30 PM
Room: 110 + 140
Description: 

The collision and convergence between the Indian and Eurasia plates caused continuous crust uplift and shortening in Tibetan Plateau, resulting in lateral expansion of southeastern (SE) Tibetan Plateau (e.g., Yin and Harrison,2000; Zhang et al., 2004). Two end-member models, “rigid-block extrusion” and “lower crustal flow”, are generally used to understanding material escape in this region (e.g., Royden et al., 2008; Tapponnier et al., 1982). The ductile crustal flow can be characterized by low seismic velocity, high conductivity, high Poisson’s ratio and strong seismic attenuation (Bai et al., 2010; Bao et al., 2015; Chen et al., 2014; Zhao, Xie, He, et al., 2013). Some geophysical observations suggest the Emeishan Large Igneous Province (LIP) located in SE Tibetan plateau blocked the possible crustal flow and question the importance of the lower crustal flow (Bao et al., 2015; Yang et al., 2019). To investigate fine geometry or inter-connectivity of the possible crustal material flow, we conduct high-resolution crustal attenuation tomography to check strong attenuation distribution across SE Tibetan Plateau based on ChinArray Lg data. About 40 thousand vertical-component digital seismograms were collected at 1012 stations from 134 regional earthquakes between Jun. 2000 and Sep. 2017. An Lg-wave attenuation tomography methods (Zhao and Xie, 2016; Zhao et al., 2010) was applied to construct a broadband Lg attenuation models with resolution up to 0.3 degree. The results are highly consistent with the previous studies (Bao et al., 2015; Fu et al., 2017; Li et al., 2016). There is a relative high Q anomaly in the northwest Diandong block, inferring for the inner-core of the Emeishan LIP, which limb the low Q anomalies into small branches, one around it shows a probably connection between two strongly attenuated regions, the ChuanXi block and the DianZhong blocks (DZB). This work was supported by the Special Fund of China Seismic Experimental Site (2019CSES0103, 2018CESE0102 and 2016CESE0203) and the National Natural Science Foundation of China (41630210 and 41674060).

Presenting Author: Yishan Song

Authors