固体地球物理专业研究生学术论坛——胡少乾

A M_s 6.9 magnitude earthquake occurs in November 18th, 2017 in southeastern Tibet, which is the largest in and around the East Himalayan Syntaxis for the last 50 years. To further understand the nucleation mechanism of this earthquake and distribution of local seismicity, as well as regional tectonics, detailed crustal velocity structure is obtained by the direct ambient noise tomography using Rayleigh wave phase velocity data in period band 5 -- 40s in this area. The spatial correlation of the velocity model and the distribution of the seismicity reveals that the nucleation mechanism of the Mainling 2017 M_s 6.9 earthquake is closely related to the local stress condition and velocity structure, as well as the aqueous fluid and geothermal state. Our velocity model is comparable with previous magnetotelluric inversion results and reveals the distribution and connectivity of the low velocity zones (LVZs). General patterns show LVZs in the north-west and high velocity zones in the south-east which are truncated by major faults. We also found a relatively low velocity anomaly in the upper crust near Namche Barwa massif, which can be explained by the conceptional tectonic aneurysms' model that emphasizes the coupling effects of climate, erosion, and tectonics. To reconcile our velocity model with previous observations, we propose a tentatively integrated geodynamic model for upper mantle to surface to explain the local seismicity and stress condition.