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Seismogenic structure in the source zone of the 1918 M7.5 NanAo earthquake in the northern South China Sea
Xia, Shaohong1,3; Zhou, Pengxiang4; Zhao, Dapeng2; Cao, Jinghe1,3
2020
Source PublicationPHYSICS OF THE EARTH AND PLANETARY INTERIORS
ISSN1872-7395
Volume302Pages:106472
AbstractAs a typical rifted margin, the coastal region of the northern South China Sea has experienced many large crustal earthquakes in the past 400 years. For example, two destructive earthquakes with similar to M7.0 in 1600 and similar to M7.5 in 1918 occurred close to the NanAo Island. However, the mechanism of these earthquakes and seismotectonics of the region are still unclear. In this work we make the first study of the detailed three-dimensional crustal structure in the source zone of the 1918 NanAo earthquake (M7.5) using newly acquired wide-angle seismic reflection data. Our results show that current seismicity mostly occurred in a midcrustal low-velocity zone or its nearby high-to-low velocity transitional areas. We ascertain locations of the ENE-strike Littoral fault zone and the NW-strike Huanggangshui fault based on the seismic reflection profiles. These faults have caused a large-scale vertical dislocation of the sedimentary basement. The structure of the upper crust is very heterogeneous, containing many high or low velocity anomalies. However, the lower crustal structure is less heterogeneous, mainly characterized by low velocity mostly in the northern part of the study area and high velocity mainly in the southern part. The crust in the seismicity zone shows strong heterogeneity, reflecting highly cracked structural features possibly caused by destructive earthquakes. We infer that the midcrustal low-velocity zone and the intersection between the Littoral fault zone and the Huanggangshui fault could reflect weak structures in the crust and form a local stress buildup, which strongly affected or controlled the generation of intraplate seismicity. The 1918 NanAo earthquake very likely occurred within the current seismicity zone with a depth range of 15-25 km estimated from our tomographic images and previous geological and geophysical results.
DepartmentOMG
KeywordCrustal structure Intraplate seismicity 1918 NanAo earthquake South China Sea Midcrustal low-velocity zone
DOI10.1016/j.pepi.2020.106472
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Document Type期刊论文
Identifierhttp://ir.scsio.ac.cn/handle/344004/18553
Collection中科院边缘海地质重点实验室
Affiliation1.Chinese Acad Sci, South China Sea Inst Oceanol, CAS Key Lab Ocean & Marginal Sea Geol, Guangzhou, Peoples R China
2.Southern Marine Sci & Engn Guangdong Lab Guangzho, Guangzhou, Peoples R China
3.Tohoku Univ, Grad Sch Sci, Dept Geophys, Sendai, Miyagi, Japan
4.Chinese Acad Sci, Innovat Acad South China Sea Ecol & Environm Engn, Guangzhou, Peoples R China
5.Univ Chinese Acad Sci, Beijing, Peoples R China
Recommended Citation
GB/T 7714
Xia, Shaohong,Zhou, Pengxiang,Zhao, Dapeng,et al. Seismogenic structure in the source zone of the 1918 M7.5 NanAo earthquake in the northern South China Sea[J]. PHYSICS OF THE EARTH AND PLANETARY INTERIORS,2020,302:106472.
APA Xia, Shaohong,Zhou, Pengxiang,Zhao, Dapeng,&Cao, Jinghe.(2020).Seismogenic structure in the source zone of the 1918 M7.5 NanAo earthquake in the northern South China Sea.PHYSICS OF THE EARTH AND PLANETARY INTERIORS,302,106472.
MLA Xia, Shaohong,et al."Seismogenic structure in the source zone of the 1918 M7.5 NanAo earthquake in the northern South China Sea".PHYSICS OF THE EARTH AND PLANETARY INTERIORS 302(2020):106472.
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