Seism-Tectonic Background,Deep Rheological Structure and Triggering Mechanism of Diqing Earthquake (M s 5.9),Yunnan
He Chicheng
Li Xianrui
Wang Jie
Zeng Zuoxun
Abstract：At 08∶04 of August 31st,2013,an earthquake with a magnitude of Ms 5.9 occurred in Shangrila county of Tibetan Autonomous Prefecture,Yunnan Province (28.1°N,99.4°E).The depth of the hypocenter is 10 km.The study area is seismical-ly active in history and prone to earthquake in northwestern Yunnan.Then the focal mechanism solutions show that the Diqing Ms 5.9 earthquake is of normal faulting with dextral strike-slip and the attitude of the NW nodal plane is consistent to the De-qin-Zhongdian fault.In this paper,we discuss the bouguer anomaly near the epicenter using EIGEN-6C2 model,and the epi-center is located at the Moho depth undulating position,and place where the crustal thickness is unstable.From the profile of P wave velocity and crustal structure,we know that low-velocity layer exists at the bottom of the upper crust,and the layer is likely to be closely related to seismic energy accumulating and storing.The joint location of the edge of the low-velocity (high conductivity)layer and the Deqin-Zhongdian fractures is the location for the focus to release the accumulating energy.This pro-vides a new case of the three-level tectonic model for intra-plate earthquake.
Keywords：earthquakegravity anomalyrheological structureDeqin-Zhongdian fracturesthree-level tectonic model
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：14( 1653-1666 )