Joint inversion of receiver function, ambient noise dispersion, and Rayleigh wave ZH ratio for the crustal structure beneath the northeastern margin of the Tibetan plateau and its surrounding regions

We process the continuous waveform data recorded by 571 broadband temporary seismic stations in the northeastern (NE) margin of the Tibetan plateau and its surrounding regions, and jointly invert the ambient noise dispersion, Rayleigh wave ZH ratio, and P-wave receiver function to obtain high-resolution 3D S-wave velocity structure (V-S) of the crust. The results demonstrate that significant low-velocity anomalies of S-wave appear in the depth interval of 15 similar to 40 km beneath the Songpan-Garze block and the western Qinling orogen as well as the northern Qilian orogen. The low-velocity zone below the Songpan-Garze block and the western Qinling orogen may be related to the crustal partial melting, and the causes of partial melting are not only shear heating but also asthenosphere material upwelling and crustal radioactivity. While that of the northern Qilian orogen may be related to surface uplift and crustal thickening. Many insignificant low-velocity anomalies are observed beneath the Alxa block, which may be related to the complex tectonic deformation of the Alxa block. Relatively insignificant low-velocity anomalies are also observed at the depth interval of 20 similar to 35 km beneath the Yinchuan-Hetao graben, which is more likely to be related to the underplating of mafic magmas.