Seismic attenuation tomography in southwestern China: Insight into the evolution of crustal flow in the Tibetan Plateau

Abstract

Crustal flow in southwestern China is commonly attributed to the continental collision between the Indian and the Eurasian plates. Therefore, studying crustal flow in this area can provide valuable insight into the collisional process. The quality factor (Q) is an indicator of seismic wave attenuation that provides constraints on lithology, rheology, and geodynamic processes, which are vital for interpreting the nature of the crustal flow in a given region. In this study, we used local seismic waveforms to obtain regional attenuation models for P- (QP) and S- (QS) waves in the Sichuan-Yunnan region (SYR). The Emeishan Large Igneous Province (ELIP) is characterized by high QP and QS values in the Middle Yunnan block (MYB) at depths greater than 5 km. The QP and QS values in most of the fault zones surrounding the MYB were lower than 300, indicating that the material within crustal faults causes high waveform attenuation. Our results suggest that the crustal flow was diverted into two channels in the northern MYB due to resistance from the ELIP. To illuminate the tectonic dynamics of the SYR, we propose a simple model that explains both the evolution of the crustal flow and the variation in the seismic wave attenuation.