五大连池火山区地震活动与岩浆作用关系研究

The Wudalianchi volcanic field is located in Northeast China, and its latest eruption was about 300 years ago. In recent years, there are seismic activities in the volcanic field. However, whether these earthquakes are related to the magmatism is still not clear. Seismic moment tensor solution and micro-earthquake location can provide important information about the source rupture process and fluid migration, which is a crucial way to understand the relationship between seismic activity and magmatism. In this study, we inverse the small earthquake moment tensors and detect micro-earthquakes jointly using the waveform data recorded by dense temporary and permanent stations, and attempt to get more reliable moment tensors and a more complete earthquake catalogue. The volume change of moment tensor solution and the patterns of micro-earthquakes migration with time are analyzed to discuss the relationship between seismic activity and magmatism. This study will provide a new perspective for the present magmatic characteristics in Wudalianchi volcanic field, as well as an important scientific reference to the future volcanic risk assessment. The results can also provide basic data for China Geophysical Reference Model.

五大连池火山位于我国东北地区，最近一次喷发约在300年前。近年来，火山区存在有地震活动，这些地震活动是否与岩浆作用有关目前并不十分清楚。地震矩张量解和微震迁移特征能够有效反映火山区的流体作用。本研究将固定台站与密集流动地震观测相结合，采用小震矩张量反演方法及波形模板匹配技术，获取火山区可靠的小震矩张量解和更为完备的微震目录，分析小震矩张量解中的体积变化分量，并探讨微震随时间的迁移特征。综合分析这两种研究结果，探讨五大连池火山区地震活动与岩浆作用的关系，试图揭示火山区现今岩浆活动状态，从而为判定未来火山活动危险性提供重要科学依据。本项目研究结果也可为中国区域地震参考模型提供基础资料。

本项目采用五大连池火山区布设的密集流动地震台站连续观测波形数据，运用深度学习方法和微震关联技术获得133个微震事件，结果显示地震在整个火山区均有分布，并未发现围绕火山口的丛集分布特征；且在火山锥（格拉球山、卧虎山、笔架山、老黑山、火烧山）附近的地震事件表现出沿断裂北东向的展布特点。基于改进的小震矩张量反演方法获得2011年五大连池4.2级地震全矩张量解，其中双力偶成分占95%，为剪切破裂模式。进一步基于深源地震Moho面转换震相Sp，获取了五大连池火山区下方精细的Moho面结构，结果表明在五大连池火山区的下方Moho面表现出下凹的趋势，推测壳内岩浆囊的存在是Moho局部下沉的重要原因。综合以上结果，本研究认为五大连池火山区的微震事件与区域断裂密切相关，地震活动与壳内岩浆囊作用没有表现出一定的相关性。

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