Different Formation Modes of the North–South-Trending Rifts in Southern Tibet: Implications From Ambient Noise Tomography

Abstract

Understanding how the Miocene N–S-trending rifts on the southern Tibetan Plateau formed is crucial for understanding the evolution of the plateau. Most competing models suggest that all the rifts developed uniformly, but there are differences in magmatism among them. We conducted ambient noise tomography based on a broadband seismic array deployed across the rifts. A mid-crustal low-Vs layer extends laterally beneath the Tangra Yum Co Rift and the Pumqu-Xianza Rift, implying that E‒W stretching of the ductile middle crust segmented the brittle upper crust, causing rifting and subsequent magmatism. In contrast, the Yadong-Gulu Rift, which experienced prerifting magmatism, is characterized by an isolated low-Vs anomaly extending subvertically from the surface to the middle crust, indicating that the crust experienced magmatic intrusion and local disruption, which promoted the later formation of a large rift. The results suggest that the various rifts might have distinct formation modes.