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本文选取不同的地壳速度分区模型,应用双差定位法对2008—2017年发生在青藏高原东缘的地震进行了重新定位,共得到4921个精确定位结果.重定位后的地震更加集中分布于龙门山断裂带、鲜水河断裂以及四川盆地南缘,震源深度多为5~20 km.根据NGDC-720地磁场模型计算了青藏高原东缘的三分量磁异常及其梯度张量,重定位后的大多数地震位于负磁异常区域以及四川盆地西南缘的强-弱磁异常边界.基于三维分形磁化模型获得了青藏高原东缘的居里点深度,并计算了磁性层的平均地温梯度,进而利用一维稳态热传导方程获得了其地壳温度结构.结果显示青藏高原东缘大多数地震均发生在居里点深度较大、地温梯度较低的区域.大多数M≥2.0地震震源区温度为100~500℃,M≥4.0地震震源区温度多为200~400℃.2008年汶川MS8.0、2013岷县MS6.6、2014年鲁甸MS6.5以及2017九寨沟MS7.0地震震源区温度均为300℃左右,而2013年芦山MS7.0地震震源区温度接近约400℃,更多地受控于龙门山断裂带与鲜水河断裂交汇处的局部构造应力场异常. 相似文献
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利用NGDC-720全球卫星岩石圈磁场模型给出的球谐系数,计算得到中国及邻区的岩石圈磁场分布;并与该地区活动块体及近10年(2003-2012年)MS 5.0以上地震活动性进行对比,发现岩石圈磁场同活动块体分布及地震活动性存在较为密切的对应关系。该相关性有望在未来地震研究和监测中发挥作用。 相似文献
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The lithospheric magnetic field (LMF) in China and its surrounding are calculated using the spherical harmonic coefficients given by the NGDC-720 model. The LMF comes from the magnetization of minerals in the crust and in the uppermost mantle. It may, therefore, provide unique insight into lithospheric tectonic processes and mechanisms. Here, we study the geomagnetic manifestation of active tectonic blocks, and find a close correlation between the LMF and seismicity. Many large faults are found to closely overlap with magnetic anomalies, or are distributed along the boundaries of magnetic anomalies. Earthquakes in these fault regions have occurred on the boundaries of magnetic anomalies, or in the transition zones between positive and negative anomalies. We analyze the components of the LMF, and the LMFs at different altitudes, finding that the vertical component, B z at 200 km, is the most related to seismic activity. Relevant physical mechanisms are also discussed. We propose that the stress or viscosity differences caused by temperature variations, which manifest in the LMF, may be the predominant reason for the correlation between the LMF and seismic activity along large faults. 相似文献
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