Rupture directivity and seismogenic structures of strong aftershocks in the northeastern rupture zone of the 2008 Wenchuan earthquake

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Ting Liu, Xiaohui He, Yipeng Zhang, Zhiliang Liu, Wenjun Zheng, Peizhen Zhang, Yi Wang
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引用次数: 0

Abstract

Three strong aftershocks (MS6+) occurred in the northeastern rupture zone of the 2008 MW7.9 Wenchuan earthquake within three months. No surface ruptures were observed, and the seismogenic faults remain unclear. Resolving the source parameters and seismogenic structures of these strong aftershocks is essential for clarifying the rupture termination mechanism of the mainshock and for future seismic hazard assessment. In this study, we determined the point source parameters of eight moderate to strong aftershocks and the rupture directivity of three strong aftershocks through regional and teleseismic waveform modeling. The focal mechanisms of these aftershocks are diverse, including both strike-slip and thrust-slip types, with centroid depths ranging from the middle crust (12–19 km) to the shallow part (3–5 km), highlighting the complexity in the rupture termination zone. The rupture directivity analysis shows that the strike-slip May 25 event (Mw6.0) ruptured from SW to NE along the right-lateral plane (60°/81°/173°) for ∼7 km, the strike-slip July 24 event (Mw5.5) on ruptured from NNE to SSW along the right-lateral plane (16°/67°/147°) for ∼6 km, and the thrust-slip August 5 event (Mw5.9) ruptured upwards along the northeast dipping plane (339°/56°/83°) for 6–8 km. The strike of ruptured faults changes from NE to NNE, differing from the Qingchuan fault. The estimated stress drop of the event in the middle crust (∼19 km, 9.3 MPa) is larger than that of the shallower event (∼4 km, 1.9 MPa), possibly due to the low strength of the shallow crust. Moreover, the rupture direction of the July 24 event is opposite to that of the mainshock, potentially due to the Bikou block's differing bi-material contrast, which may have hindered the northeastward extension of the mainshock's rupture.
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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