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2013年8月31日8时4分,云南省迪庆藏族自治州香格里拉县(28.12°N,99.4°E)发生5.9级地震,震源深度10km.区域范围内历史地震频繁,为滇西北地震多发区.据震源机制解结果,此次地震为正断兼左旋走滑型地震,NW向截面产状与德钦-香格里拉-中甸断裂基本吻合.利用EIGEN-6C2模型对震中附近进行布格重力异常探讨,震源位置位于莫霍面起伏部位,下部地壳厚度不稳定之处;而从P波速度与地壳结构剖面可知研究区上地壳底部存在低速层,认为韧性低速层与地震能量的积聚和存储关系密切.而韧性低速(高导)层与德钦-中甸断裂交接部位,是流变界面能量释放的位置,即本次地震的震源位置.这为板内地震3层次构造模式提供了一个新的案例.
At 08:04 on August 31, 2013, an earthquake of magnitude 5.9 occurred at 28.12 ° N, 99.4 ° E in Diqing Tibetan Autonomous Prefecture, Yunnan Province, with a focal depth of 10 km. The historical earthquakes in the area are frequent and occur frequently in areas prone to earthquakes in Northwest Yunnan According to the result of focal mechanism solution, the earthquake is a normal-strike-slip and left-slip strike-slip earthquake, and the NW-sectioned section shape basically agrees with the Deqin-Shangri-La-Zhongdian fault.The Bouguer gravity anomaly near the epicenter by EIGEN-6C2 model From the P-wave velocity and the crustal structure profile, it can be seen that there is a low-velocity layer at the bottom of the upper crust of the study area, and it is considered that the relationship between the low-velocity ductile layer and seismic energy accumulation and storage And the junction between low ductile (high conductance) layer and Deqin-Zhongdian fault is the energy release site of rheological interface, that is, the source location of this earthquake, which provides a new 3-level tectonic mode for on-board earthquakes The case.