Jiang Hanchao, Zhong Ning, Li Yanhao, Ma Xiaolin, Xu Hongyan, Shi Wei, Zhang Siqi, Nie Gaozhong
State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing, 100029, China.
College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2017 Nov 16;7(1):15686. doi: 10.1038/s41598-017-16027-8.
Lacustrine sediments on the eastern Tibetan Plateau (TP) contain a wealth of information on local and regional tectonic activity. High-resolution grain-size and magnetic susceptibility measurements were conducted on the 23.4-m-thick Lixian lacustrine sedimentary sequence spanning from 19.3 to 6.0 ka, revealing 70 prehistoric seismic events on the eastern TP. The seismic events caused intermittent increases in source materials that endowed the samples of an individual event layer with a gradual fining trend along the C = M line on a C (one percentile)-M (median diameter) plot. Grain-size distribution and end-member modeling imply that dust particles of <20 μm in size were transported primarily by long-term suspension, while medium to coarse silt and sand were transported primarily by short-term suspension, such as aeolian transport constrained by local topography. Provenance analysis based on U-Pb zircon ages indicates that dust particles generated by earthquakes at Lixian had no effect on dust deposition at Xinmocun and Diaolin, and vice versa. These prehistoric seismic events, revealed by variations in grain size and magnetic susceptibility, thus provide invaluable information on the long-term behavior of local seismic activity.
青藏高原东部的湖相沉积物蕴含着丰富的关于当地及区域构造活动的信息。对跨度为19.3至6.0千年、厚度为23.4米的理县湖相沉积层序进行了高分辨率粒度和磁化率测量，揭示了青藏高原东部70次史前地震事件。这些地震事件导致源物质间歇性增加，使得单个事件层的样本在C（百分之一粒径）-M（中值粒径）图上沿着C = M线呈现出逐渐变细的趋势。粒度分布和端元模型表明，粒径小于20微米的尘埃颗粒主要通过长期悬浮作用搬运，而中粗粉砂和砂主要通过短期悬浮作用搬运，如受当地地形限制的风成搬运。基于U-Pb锆石年龄的物源分析表明，理县地震产生的尘埃颗粒对新磨村和吊林的尘埃沉积没有影响，反之亦然。因此，这些通过粒度和磁化率变化揭示的史前地震事件，为当地地震活动的长期行为提供了宝贵信息。
