Spatial variations of current tectonic stress field and its relationship to the structure and rheology of lithosphere around the Bohai Sea, North China. (15th May 2017)

• Record Type: Journal Article
• Authors: Li, Xianrui; Wang, Jie; Zeng, Zuoxun; Dai, Qingqin
• Is Part Of: Journal of Asian earth sciences. Volume 139(2017)
• Page Start: 83
• Page End: 94
• Publication Date: 2017-05-15
• Subjects: Rheology -- Focal mechanism solutions -- Tectonic stress field -- Low-velocity body -- Bohai sea; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2016.12.023
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Focal mechanism solutions of 62 earthquakes in circum-Bohai-Sea area are presented. Circum-Bohai-Sea area is predominantly under a strike-slip faulting stress regime. Maximum principle axes are oriented horizontally in NEE-SWW or nearly E-W direction. Localized normal faulting stress regimes are observed in Tangshan and Haicheng areas. The normal faulting stress regimes are caused by strike-slip transtension. Abstract: The tectonic stress field in the middle-upper crust is closely related to the structure and rheology of the lithosphere. To determine the stress field in the deep crust, we inversed the focal mechanism solutions (FMSs) of 62 earthquakes that occurred between 2009 and 2015 in the Bohai Sea and its surrounding areas using broadband seismic waveforms collected from 140 stations. We then derived the tectonic stress field using the software SATSI (Spatial And Temporal Stress Inversion) based on the damped linear inversion method. The inversion results show that both the maximum (σ1 ) and minimum (σ3 ) principle stress axes throughout the entire region are nearly horizontal except in the Tangshan and Haicheng areas, suggesting that the study area is predominantly under a strike-slip faulting stress regime. The σ1 and σ3 axes are found to be oriented in the NEE-SWW or nearly E-W and NNW-SSE or nearly S-N directions, respectively. These results indicate that the stress field in the North China Craton is controlled by the combined effects of the Pacific Plate westward subduction and the India-Eurasia Plate collision. However, localized normal faulting stress regimes (where the vertical stress σv ≈ σ1 ) are observed in the Tangshan and Haicheng areas, where low viscosity bodies (LVBs) were identified using geophysical data. Based on the analysis of focal mechanism solutions, active faults and lithosphere rheology characteristics in the Tangshan and Haicheng areas, we speculate that the anomalous stress regime is caused by the local extension resulting from the movement of strike-slip faults under the action of the regional stress field. The existence of LVB may indicate weakness in the crust that favors the accumulation of tectonic stress and triggers large earthquakes.