摘要
地震序列的特征和震型判定工作有助于抗震救灾工作的开展,对其发生成因的研究是解决地震预报难题必须面对的科学问题。汶川8.0级地震序列的初步研究表明:①余震沿龙门山断裂带分布于宽100km,长约330km的带状区域内,并侧向于主震震中的北侧;②序列发展初期有2个快速衰减过程;③序列类型为主震—余震型,最大强余震6.4级;④序列的空间演化过程,强余震震源机制结果和地震精确定位结果分析表明,序列具有分段特征;⑤8.0级地震的发震构造是龙门山断裂带,发震构造在剖面上呈现出"犁形"或"铲形"。地球物理勘探和壳、幔结构反演结果表明,自青藏高原穿越龙门山到四川盆地存在地幔阶梯,上地幔阶梯的阻挡作用使得物质东移速率减慢,并蕴积了汶川8.0级地震所需能量。地震的产生正是东西向应力平衡被打破的结果,余震沿龙门山断裂的分布是高原地壳在印度板块的推挤作用下向北北东方向的运动得以继续的表现。整个龙门山断裂带都参与了活动,龙门山断裂带北端作为断裂带的止裂端与南段同期活动。
The features of Wenchuan M8.0 earthquake and judgment of the sequences are useful to develop the work of earthquake relief. The research of the causes of great earthquakes are useful to realize the earthquake prediction and forecast. The study results show that： （1） The aftershocks of the earthquake distributed along the Longmenshan mountain fault zone, and mainly in the north side of the mainshock, the earthquake zone is 100km width, about 330km length. （2）There were two rapid energy attenuation in early period of the sequence. （3） The type of Wenchuan M8.0 earthquake sequences was judged to be main-aftershock pattern. The max aftershock is Qingehuan M6. 4 earthquake on May 25,2008. （4） Time-space evolution, the focal mechanism of bigger aftershock and the results of aftershock precisely location in the sequence proved that the sequence shows an obvious segmented feature. （5） The Longmenshan mountain fault zone is major triggering seismic fault with spade fault profile. A step of moho depth form Tibet to Sichuan basin, crossed through Longmenshan mountain, was revealed by the result of geophysical exploration and inversion of Crust-Mantle velocity structure. The step is a barrier of the crust of Tibet eastward movement and makes the movement rate slowed down and great energy of M8. 0 Wenchuan accumulated. The broken east-westward stress balance generates the earthquake. The aftershocks of the sequences show zonal distribution along to Longmenshan mountain fault zone, and it＇ s the result of north-eastward movement under the broaching of India plate. The south section and north end of the Longmenshan mountain fault zone moved simultaneously and the all fault zone was actived.
出处
《高原地震》
2009年第3期1-10,共10页
Plateau Earthquake Research
基金
地震科学联合基金(C07048)
关键词
汶川8.0级地震
序列
分段特征
成因
地幔阶梯
Wenchuan 348.0 Earthquake
Earthquake sequence
Segmentation features
Causes
Step of Moho depth
