Upper crustal anisotropy from local shear-wave splitting and crust-mantle coupling of Yunnan, SE margin of Tibetan Plateau

3-D azimuthal anisotropy structure reveals different deformation modes of the crust and upper mantle in the southeastern Tibetan Plateau

“…Therefore, we prefer that the low-velocity anomaly east of the XJF is most likely caused by in situ plastic deformation and/or partial melting (Zhang et al, 2020) due to crustal thickening and strong deformation. The fast axis direction in these two low-velocity anomalies is subparallel to the trend of low-velocity anomalies (Figures 10C, F) and consistent with the local shear wave splitting results (Zhang and Gao, 2017;Zhang et al, 2018) and receiver functions (Sun et al, 2012;Cai et al, 2016;Zheng et al, 2018) (Figure 7B). The fast axis direction may indicate the migration direction of the low-velocity material.…”

“…However, the fast axis changes to the NW-SE direction in the southeastern part of the Red River Fault within our study area (Figure 8B), which probably represents the fossil anisotropy reformed by the episodic strike-slip of the fault in the Cenozoic. The shear wave splitting parameters from local events (Zhang and Gao, 2017;Zhang et al, 2018) and the Pms phase (Sun et al, 2012;Cai et al, 2016;Zheng et al, 2018) also show similar results (Figures 8A, B). The central area of the South Chuandian Block shows high velocity and weak anisotropy (Figure 10F), but the azimuthal anisotropy is strong and shows a fault-parallel fast axis direction in the boundary of the South Chuandian Block (Figure 10C, F), which indicates that the deformation within the upper crust is concentrated at the block boundary and faults.…”

“…The quantitative differences between the predicted and observed data are shown in Supplementary Figures S8-S10. The observed shear wave splitting parameters we compared in the crust are inverted from local events (Zhang and Gao, 2017;Zhang et al, 2018) and Pms phase data (Sun et al, 2012;Cai et al, 2016;Zheng et al, 2018), which are mainly sensitive to crustal anisotropy. The observed data from the XKS phase (Chang et al, 2008;Chang et al, 2015;Chang et al, 2017), representing the integrated effect of anisotropy along the ray path, were compared with the upper mantle anisotropy (<200 km) inferred from surface wave tomography.…”

Shear Wave Splitting of the 2018 Lombok Earthquake Aftershock Area, Indonesia

“…3) and Table 1, we observe that the fast polarizations at most of the observation stations tend to vary in some different areas. Eken et al (2011) and Zhang et al (2018) suggested that in the earth's crust, the ф at an observation station is relatively parallel to the strike of the local fault. Furthermore, the SWS studies conducted around the strike-slip fault area generally show that the ф at stations adjacent to the fault zone tends to be parallel to the strike of the fault (Audet, 2014;Boness and Zoback, 2006).…”

The 2007 Ning'er Mw 6.1 Earthquake: A Shallow Rupture in Southwest China Revealed by InSAR Measurements

“…The underthrust rate of Indian Plate to the Tibet plateau is about 50 mm/year (Minster & Jordan, 1978), causing the crust of Tibetan plateau to shorten, uplift, and make the surrounding blocks escaped (Zhang et al, 2005), which not only strongly influences the geomorphology and seismic activity in western China but also makes the Sichuan-Yunnan rhombic block (SYRB) move to south and southeast in a clockwise direction at different rates (Qiao et al, 2004;Li et al, 2014;Zhang et al, 2003). The Ning'er earthquake occurred in the Simao-Puer area, a region has been a NE trending massive uplift structure in the middle of sag (Guo et al, 1999;Zhang et al, 2018; Figure 1). On the south side of the uplift area, a set of nearly EW trending reverse faults have been developed, which are imbricate and S shaped.…”