Journal
TECTONOPHYSICS
Volume 845, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.tecto.2022.229642
Keywords
Fault geometry; Earthquake relocation; Focal mechanism; Seismic tomography; Ms 7; 8 Tangshan earthquake
Categories
Funding
- National Institute of Natural Hazards, Ministry of Emergency Manage-ment of China
- National Natural Science Foundation of China
- [ZDJ2020-09]
- [ZDJ2019-16]
- [41804053]
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Investigating the fine structure of fault zones is essential for understanding the mechanism of large earthquake nucleation. The study on the complex fault geometry of the Tangshan fault zone in North China provides detailed information on the fault zone structural features and suggests that the ascending of hot mantle material into the lower crust may have weakened the Tangshan fault zone and generated the 1976 Ms. 7.8 Tangshan earthquake.
Investigating the fine structure of fault zones is essential for understanding the mechanism of large earthquake nucleation. In this paper we study the complex fault geometry of the Tangshan fault zone in North China using a new seismic data set from 2010 to 2020 that spans-10 years. Based on the well-located hypocenters and focal mechanism solutions, we obtained more detailed information on the fault zone structural features: (1) the fault zone is divided into five segments according to different dip angles of the fault plane; (2) the spatial distribution of seismicity reveals conjugate fault branches and a flower-shaped structure at the northern part of the fault zone; and (3) the fault zone is dominated by a strike-slip type, but their intersecting segments are characterized by a normal-fault type. We further obtained high-resolution seismic images of Vp, Vs and Vp/Vs around the Tangshan source region. Combining the fault geometry with the low-velocity anomalies below 10 km depth, we infer that the ascending of hot mantle material into the lower crust may have weakened the Tangshan fault zone and generate the 1976 Ms. 7.8 Tangshan earthquake.
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