Imaging the lithosphere-asthenosphere system with teleseismic scattered waves
The lithosphere-asthenosphere system is key to understanding plate tectonics and Earth's evolution. However, many important questions about this key part of our planet, for example, the origins of the lithosphere-asthenosphere boundary (LAB) and the enigmatic mid-lithospheric discontinuities (MLDs), remain open, which require further investigations. I am addressing these problems via imaging the discontinuities in the lithosphere-asthenosphere system by jointly analyzing multiple types of teleseismic scattered-wave data, including teleseismic-S reflections and P and S receiver functions. This approach not only allows me to resolve the structures with higher fidelity but also holds the potential to constrain parameters such as anisotropy variation, which cannot be obtained with only one type of observation. My first paper on this project is recently accepted by JGR, with more to come soon.
Post-critical SsPmp and its applications
In recent years, Virtual Deep Seismic Sounding (VDSS) has emerged as a novel method to image crustal structure. However, the nature of post-critical SsPmp, the seismic phase used in VDSS, is not well understood, which hampers the application of this method. During my PhD, I have conducted a systematic investigation into post-critical SsPmp, which resulted in a trilogy of papers that thoroughly explored the structure sensitivity of SsPmp and proposed improved methods to image lithosphere structures with this phase in 1D and 2D (Liu et al., 2018; Liu et al., 2019; Liu et al., 2020).
InSAR study of seismic "bright spots" in the Tibet Plateau
The Tibet Plateau is an excellent natural laboratory for the study of continental collision. Previous seismic reflection experiments have found seismic "bright spots" at mid-crustal level beneath different parts of the Tibet Plateau, which are usually interpreted as the accumulations of partial melt in the crust. In my AGU presentation, we show that there is no detectable ongoing surface deformation on top of the seismic "bright-spots" beneath the Yadong-Gulu Rift in southern Tibet, which argues against the interpretation of them as partial melt.
Insights on lithospheric architecture of the Tibet Plateau from Helium isotope signature
Despite nearly 30 years of continuous efforts, geophysicists failed to reach an agreement on if the Indian Plate is underplating or subducting beneath Tibet Plateau. We decided to address this issue with a different approach, that is to measure the helium isotope ratio (He3/He4) in geothermal fluids sampled from the Tibet Plateau, which is a robust indicator of incipient mantle melting beneath the sample site. Our preliminary results show that an elevated He3/He4 ratio is observed as far south as the Yarlung Suture, which combined with recent seismic models suggests that a thin layer of warm asthenospheric mantle exists between the cold Indian Plate and the Tibet crust. Our paper on this discovery is currently under review with Nature Geoscience.