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2023年土耳其双震震源处的断裂几何形状与应力场

Fault geometry and stress field around the 2023 Turkey earthquake doublet
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摘要 2023年土耳其东南区域的东安纳托利亚断裂附近发生两次大于7级的大震,震后大量余震位置及震源机制数据为求解东安纳托利亚东南段的断裂形状和区域应力场提供了良好的基础.本研究首先搜集了土耳其双震序列之后的精定位结果,采用模糊聚类求解断层面的方法求解得到了双震余震集中区的8条子断层的几何形状.结果表明MW7.8级地震的4个子断层均为较陡、倾向西北的断层,与东安纳托利亚断裂的东北段的倾向一致;MW7.6级地震主破裂为陡倾北的断层,西端存在2条相向倾向、走向西北-东南的子断层,东端存在1条走向东北、倾向与东安纳托利亚断裂相向的断层.这些结果为精细研究地震破裂模型提供了基础.然后本研究搜集了土耳其双震周围的地震震源机制,分区域求解周围应力场.发现MW7.8地震破裂东北区呈现以NE-SW向挤压和NW-SE向拉张的走滑应力状态,表现了阿拉伯板块对安纳托利亚板块的斜向推挤导致的东安纳托利亚断裂走滑运动;MW7.8西南破裂区则表现为东西向拉张和南下-北上挤压的过程,此处在阿拉伯板块、非洲板块和安纳托利亚块体的交界部位,反映了非洲板块和阿拉伯板块对该地的北上向推挤和安纳托利亚块体被迫西向运移导致的东西向拉张状态;位于安纳托利亚块体内部的MW7.6地震破裂区应力场则表现为近南北向挤压和西下拉张,反映了阿拉伯板块和非洲板块的推挤作用和该块体的西向伸展的状态.将地震破裂应力场投影到这两次地震的震源机制中心解节面上,发现MW7.8地震的应力释放方向与构造应力场方向较为一致,而MW7.6地震发震断层面的应力释放方向与构造应力场方向相差较大,表明MW7.6可能受到MW7.8地震的触发而发生. Two MW>7 earthquakes occurred near the East Anatolia fault(EAF)in southeast region of Turkey in 2023.Distribution and focal mechanism of a large number of occurred aftershocks provide a good foundation for estimating the fault geometry and regional stress field in the southeast segments of the EAF.In this study,the refined positioning result of the aftershocks of the earthquake sequence is collected,the geometry parameters of the 8 sub-faults in 8 clustering zones are estimated by using the method of fuzzy clustering and fault plane estimating.The results show that the 4 steep sub-faults of the MW7.8 earthquake are dipping to the northwest,which consistent with the dip of the northeast section of the EAF;the main fault area of the MW7.6 earthquake is dip to the north,with 2 opposite dip direction and NE,NNE azimuth sub-faults at the west end and 1 dipping opposite to the EAF and NE azimuth sub fault at the east end.Then the earthquake focal mechanism around the Turkey double strong earthquakes was collected,and the stress field at each sub-region was calculated.It is found that the northeastern rupture region of the MW7.8 earthquake presents the strike-slip stress state with NE-SW compression and NW-SE extension,which shows the strike-slip movement of EAF caused by the oblique pushing of the Arabian plate against the Anatolia plate.The southwest rupture zone of the MW7.8 is characterized by east-west stretching and south-upward or north-downward extrusion processes.It is located at the triple junction of the Arabian Plate,the African plate and the Anatolian block,in which the stress state reflects the EW stretching state caused by the northward pushing of the African and Arabian plates and the forced westward migration of the Anatolian block.The stress field of the MW7.6 earthquake rupture zone,which located in the Anatolian block,is characterized by the process of near NS extrusion and west-downward extension,which reflecting the pushing action of the Arabian plate and the African plate and the westward extension of the block.The stress field of the main area of the earthquake rupture is projected to the nodal planes of the central focal mechanism of the two earthquakes.It is found that the stress release direction of the MW7.8 earthquake is consistent with the direction of the tectonic stress field,while the stress release direction of the MW7.6 earthquake is quite different from that of the tectonic stress field,indicating that MW7.6 may be triggered by the MW7.8 earthquake.
作者 万永革 关兆萱 梁玮航 代潇 WAN YongGe;GUAN ZhaoXuan;LIANG WeiHang;DAI Xiao(Institute of Disaster Prevention,Sanhe Hebei 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe Hebei 065201,China;Hebei Hongshan Thick Sediment and Earthquake Disaster National Field Scientific Observation and Research Station,Longyao Hebei 055350,China Received Date:07 Octob)
出处 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2024年第12期4622-4639,共18页 Chinese Journal of Geophysics
基金 国家自然科学基金(42174074,41674055,42364005)资助。
关键词 土耳其双震 断裂几何形状 地震丛集 震源机制 应力场 Turkey earthquake doublets Geometry of fault system Earthquake clustering Focal mechanism Stress field
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