青藏高原东南部巴松措湖泊沉积物记录的晚全新世地震事件

Influenced by the collision between Eurasian Plate and Indian Plate, the southeastern Tibetan Plateau has been suffered from serious seismic events. Investigation of historical seismic events especially those continuously preserved in lacustrine sediments is essentially important for long term prediction of seismic hazards. We choose Lake Basom Tso in the southeastern Tibetan Plateau as our study area, on the eastern edge of the Himalaya Frontal Thrust. Underwater sediment cores will be collected, while varve counting, 210Pb/137Cs and AMS 14C dating results will be employed to establish the age model for the sediment sequence. Results from field seismic stratigraphy investigation, high resolution XRF-scanning and sedimentary proxies (i.e. grain size, magnetic susceptibility, total organic carbon content, mineral composition and pollen assemblage) from short sediment cores will be used to infer the sedimentary characters of known seismic event (e.g. Motuo-Zayu 1950 A.D. Earthquake) preserved in the sediments from Lake Basom Tso. Accordingly, late Holocene seismic events record will be investigated based on high resolution sedimentological analyses of long sediment cores recovered from Lake Basom Tso. Subsequently, the examination of potential temporal patterns about the seismic events, especially the recurrence time, would provide significant knowledge for the prediction and protection of regional seismic hazards. In addition, comparison with regional high-resolution sequences particularly human activity related records would lead to results about the potential influences of seismic event on regional environmental changes as well as human activities.

受欧亚板块与印度板块碰撞影响，青藏高原东南部多发地震灾害，对历史时期地震灾害尤其是湖泊沉积物中保存的连续地震事件序列开展系统研究，探讨地震发生时间规律，对地震的中长期预警具有重要意义。本项目以青藏高原东南部巴松措为研究对象，采集沉积物岩芯并利用纹层计年、210Pb/137Cs测年及AMS 14C测年方法建立沉积物的年代序列。利用沉积物浅层地震剖面分析、沉积物短岩芯高分辨率的XRF元素扫描及沉积学指标分析（粒度、磁化率、有机碳含量、矿物组成和孢粉组成）结果，探讨巴松措沉积物中保存的地震事件（如1950年墨脱-察隅地震）沉积学特征。在此基础上，利用巴松措沉积物长岩芯高分辨率沉积学指标分析结果建立该地区晚全新世阶段地震事件序列，弥补区域历史地震资料的空缺；探讨地震事件发生的时间规律，为藏东南地区地震灾害的中长期预警提供科学参考；对比区域内高分辨率记录，揭示地震事件对区域环境演化及人类活动的影响。

受欧亚板块与印度板块碰撞挤压，青藏高原地区构造活跃，地震事件频发，对区域社会经济发展造成重要影响。然而，由于地震事件的不可预见性，对地震事件的记录尤其是长时间序列的记录资料非常有限。开展湖泊水下沉积物序列研究，对揭示长时间序列连续地震事件具有重要意义。本项研究选择青藏高原东南部林芝地区的湖泊沉积物开展研究工作，获取了巴松措和措木及日两个湖泊的沉积物岩芯，开展系统的沉积学研究工作，主要工作包括：（1）对巴松措沉积物短岩芯开展年代学及沉积学指标分析，探讨沉积物岩芯对1950年察隅地震的响应过程，除年代学及沉积指标异常证据外，发现沉积岩芯中保存的粘土盖层，可作为地震扰动沉积的重要证据。（2）巴松措湖心采集到的沉积物长岩芯涵盖过去1500年历史，沉积物岩芯元素扫描、粒度、磁化率、有机碳等指标分析表明巴松措在晚全新世阶段经历了多次沉积波动事件，具体表现为沉积物粒度的突然变粗、磁化率突然升高，沉积物中陆源碎屑元素含量升高，与此同时，有机碳含量波动变化明显，经历了显著的沉积事件。（3）措木及日湖沉积物短岩芯中210Pb变化存在异常偏低的层位，记录了该湖电站闸坝修建的人为干扰沉积阶段。沉积物长岩芯涵盖了整个湖泊发育过程，包括始于全新世早期的河谷浅水相沉积阶段，由大量粗颗粒陆源碎屑物质所组成。措木及日湖自2400年前开始形成稳定的湖泊相沉积物，记录了青藏高原东南部近2000多年以来环境演化历史。本项目依托青藏高原东南部两个湖泊沉积物序列建立了该地区晚全新世环境演化序列，为深入探讨区域气候环境变化以及突发地质事件提供重要参考资料。