摘要
本文利用玛多7.4级地震科考密集台阵150个台站和固定台站MAD记录的近震波形数据,采用横波分裂分析方法测量,总计得到22518对有效横波分裂参数,获得了震源区上地壳各向异性特征.结果显示,震源区各台站的快波偏振方向和慢波延迟时间存在着明显的空间分区特征,但未能表现出随时间的规律性变化特征.最明显的横波分裂特征表现在沿主破裂余震密集区,快波偏振方向呈现出与主破裂带走向和余震序列展布较好的一致性,沿主破裂余震密集区各台站所得到的慢波延迟时间明显大于南北两侧余震密集区外台站的慢波延迟时间,且包括主震在内余震最为密集的主破裂东段的慢波延迟时间大于中段和西段,主破裂附近北侧的慢波延迟时间大于南侧.主破裂余震密集区外两侧台站的慢波延迟时间随着台站与主破裂距离的增大而逐渐减少,到一定距离后,慢波延迟时间趋于稳定.这些特征反映了玛多M_(S)7.4地震孕育过程中,应力积累主要集中在沿主破裂余震密集区,且主破裂东段的应力积累要强于中段和西段,主破裂附近的应力积累北侧强于南侧,随着距主破裂距离的增加,应力积累效应减弱,到一定距离后变得很弱.由于科考密集台阵在主震后第12天才开始布设并投入观测,这时主震和大部分强余震已经发生,并且中小地震的最高峰也过去,余震频次趋于稳定,孕震过程中积累的应力尚未释放完全,应力释放和调整过程还将持续一段时间,因此,在余震活动观测期内,分裂参数没有表现出随时间规律性的变化特征.
Based on the shear wave splitting analysis of local records waveform data at 150 temporary stations from the dense array for the Madoi M_(S)7.4 earthquake scientific expedition and a permanent station(MAD),we present a total of 22518 pairs of shear wave splitting parameters to perform a systematic analysis of the upper crustal anisotropy in the source region.The shear wave splitting results show an obvious spatial characteristics,but they don′t show regular changes with time.In the region of dense aftershock along the main rupture,the splitting results show the most obvious characteristics of shear wave splitting.The fast wave polarizations are consistent with the trend directions of the main rupture and the distribution of aftershocks.The delay times at stations in the region of dense aftershocks along the main rupture are significantly greater than these of the external.And the delay times in the eastern segment of the main rupture where the main shock occurred and aftershocks were most dense is much greater than these of the western and the middle segments,and the delay times of the north side of the main rupture is greater than these of the south side of the main rupture.Outside the region of dense aftershocks,the delay times at stations on both sides of the main rupture gradually decreases with the increase of the distance between the station and the main rupture,and reach to a certain distance,the delay times tend to stable.During the seismogenic process of the Madoi M_(S)7.4 earthquake,the stress mainly accumulated in the region of dense aftershocks along the main rupture.The stress accumulated in eastern segment of the main rupture was stronger than that in the western and the middle segments of the main rupture,and the stress accumulated on the north side of the main rupture was stronger than that on the south side of the main rupture.With the distance between station and the main rupture increased,the effect of accumulated stress gradually decreased,and the effect became very weak after a certain dist
作者
曹学来
常利军
鲁来玉
吴萍萍
郭慧丽
吕苗苗
丁志峰
CAO XueLai;CHANG LiJun;LU LaiYu;WU PingPing;GUO HuiLi;Lü MiaoMiao;DING ZhiFeng(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第5期1644-1659,共16页
Chinese Journal of Geophysics
基金
中国地震局地球物理研究所基本业务专项(DQJB21Y41)
国家自然科学基金(42074053,U1839209,41774061,41904093)资助.
