| 汶川、芦山地震前龙门山断裂带地壳形变特征对比分析 |
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| 引用本文：赵静,刘杰,任金卫,江在森,闫伟,岳冲.2019.汶川、芦山地震前龙门山断裂带地壳形变特征对比分析[J].地球学报,40(1):186-198. |
| DOI：10.3975/cagsb.2018.110201 |
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| 基金项目:国家重点研发计划项目(编号: 2017YFC1500502);国家自然科学基金项目(编号: 11672258) |
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| 中文摘要:为研究2008年汶川地震和2013年芦山地震前地壳形变特征, 本文利用1999—2015年四期GPS速度场和1990—2017年跨断层短水准资料, 对跨断层GPS速度剖面、GPS应变率场、断层闭锁程度和滑动亏损、跨断层年均垂直变化速率等进行了分析讨论, 总结了汶川和芦山地震前后龙门山断裂带三维地壳变形演化特征。结果表明, 汶川地震前龙门山断裂带中、北段处于强闭锁状态、断层面应力应变积累水平很高, 而龙门山断裂带西南段闭锁较弱、变形速率明显高于中北段、依然可以积累应力应变, 汶川地震震源位于闭锁相对弱的部位, 这可能是导致汶川地震自初始破裂点沿龙门山断裂带向北东方向单侧破裂, 而震中西南方向断层并没有发生破裂的原因之一。汶川地震的发生引起龙门山断裂带西南段应力应变积累速率加快、断层闭锁程度增强、闭锁面积增大, 这在一定程度上促进了芦山地震的发生, 而芦山地震震源位于汶川地震前强闭锁和弱闭锁的高梯度过渡部位。因为芦山地震只释放了龙门山断裂带西南段有限的应变能, 并没有显著缓解该段的地震危险性, 所以汶川和芦山地震之间的地震空段以及芦山地震西南方向的地震空段, 依然需要持续关注。此外, 本文还收集和对比分析了多次6~9级地震前地壳变形特征, 同样显示地震成核于闭锁高梯度带区域而非完全闭锁区域内部, 并且随着震级升高闭锁断层面的长度也在增大, 这一现象还需在高分辨率形变数据的帮助下进行深入研究和分析。 |
| 中文关键词:汶川地震 芦山地震 龙门山断裂带 三维变形 地震危险性 |
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| A Contrastive Analysis of Crustal Deformation Characteristics along the Longmen Shan Fault Zone before the MS8.0 Wenchuan Earthquake and the MS7.0 Lushan Earthquake |
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| Abstract:To contrastively analyze crustal deformation characteristics before the Wenchuan earthquake and the Lushan earthquake, the authors mainly used four periods GPS velocity during 1999–2015 and cross fault short leveling data during 1990–2017 to analyze the GPS velocity profiles across the fault, the GPS strain rate field, fault locking and slip deficit rate, annual vertical change rate in detail, and summarized evolution characteristics of three-dimensional crustal deformation along the Longmen Shan fault zone before and after the Wenchuan and the Lushan earthquake. The results show that the mid-northern segment of the Longmen Shan fault zone was locked tightly and stress and strain accumulation level of fault plane was very high before the Wenchuan earthquake, while the southwestern segment was locked weakly, deformation rate was significantly higher than that of the mid-northern segment, and it still could accumulate stress and strain. In addition, the source of the Wenchuan earthquake was located in relatively weakly locked position, which probably led the Wenchuan earthquake to rupture unilaterally since the initial rupture point and the southwestern segment didn’t rupture. The Wenchuan earthquake accelerated stress and strain accumulation rate of the southwestern segment and increased fault locking degree and locking area, which might, to some extent, have accelerated the Lushan earthquakes. And source of the Lushan earthquake was located in high gradient transition sites of strongly and weakly locked position before the Wenchuan earthquake. Because the Lushan earthquake only released finite strain energy of the southwestern segment of the Longmen Shan fault zone, and it did not significantly reduce seismic hazard in the segment, researchers therefore should pay attention to the earthquake empty segment between the Wenchuan earthquake and the Lushan earthquake and the segment southwest of the Lushan earthquake. In addition, the authors collected and contrastively analyzed crustal deformation characteristics before multiple earthquakes of magnitude 6 to 9, and the results also show that the earthquake nucleation was in the area of highly locked gradient zone rather than the completely locked zone, and the length of the locked fault surface increased with the increasing magnitude, which requires us to conduct in-depth research and analysis with the help of high-resolution deformation data. |
| keywords:Wenchuan earthquake Lushan earthquake Longmen Shan fault zone three-dimensional deformation seismic risk |
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